Fountain Clocks
CLUB E
Monday, July 22 2013, 10:30 am - 12:00 pm
Chair:

Krzysztof Szymaniec
NPL

IFCS-EFTF3-A1-1

Contributing to the International Atomic Time
Using an Atomic 87Rb Fountain Clock
J. Guéna, M. Abgrall, A. Clairon, S. Bize
LNE-SYRTE, Observatoire de Paris, UMR CNRS 8630, UPMC, Paris, France
Email: jocelyne.guena@obspm.fr
The second of the International System of Units (SI) is defined using the ground state hyperfine
transition of the caesium 133 atom. Today the accuracy of the widely used international atomic time(TAI) is provided by an ensemble of atomic caesium fountains worldwide used as primary frequency
standards (PFS), which give the most accurate realization of the SI second. In 2001, considering thedevelopment of new frequency standards, the Consultative Committee for Time and Frequency (CCTF)
of the Comité International des Poids et Mesures recommended that a list of secondary representationsof the second (SRS) be established to eventually be used in a new definition of the second. In 2004, a
first SRS, the 87Rb ground state hyperfine transition, was proposed. In 2012, CCTF established a list of
11 recommended transitions.
In the last years, the FO2-Rb fountain frequency standard, part of the dual Rb/Cs fountain FO21 at LNESYRTE, has reached performances in terms of precision, reproducibility and reliability, equivalent tothat of the PFSs2. The frequency measurements of a H-maser with FO2-Rb, in an almost continuous
Rb/Cs comparison over the years 2010-2012, are already worth of more than 22 monthly calibrations of
TAI. Therefore it was interesting to go throughout the process of contributing to TAI with a SRS, toexplore implications in terms of both procedures and science.
We will report the first contribution to TAI based on a SRS, here 87Rb using the FO2-Rb measurements.
We present the process from end-to-end. Asides from the fountain and its performances, we describe
how it is connected to time scales. We report on measurements of this frequency standard against LNESYRTE primary frequency standards, down to a fractional uncertainty of 4.410-16, and on theestablishment of the recommended value for the 87Rb hyperfine transition frequency. We describe theprocedure used to incorporate this secondary representation into Circular T and demonstrate the link of
FO2-Rb to the TAI ensemble with a statistical uncertainty of ~1.310-16. This work is anexperimentation of what could be done with optical frequency standards in the prospect of a redefinitionof the SI second.
This work with FO2-Rb, and more generally with the PFSs, benefits now also to the new realization of
UTC(OP), the prediction of UTC for France, which is based on a H-maser steered by the SYRTE
fountains.

1

J. Guéna et al., “Demonstration of a Dual Alkali Rb/Cs Fountain Clock”, IEEE Trans. Ultrason. Ferroelectr. Freq. Control,
vol. 57, no.3, p. 647–653, 2010.
2

J. Guéna et al., “Progress in atomic fountains at LNE-SYRTE”, IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 59,
no.3, p. 391-410, 2012.

IFCS-EFTF3-A1-2Ramsey pulling in fountain clocks
V. Gerginov, N. Nemitz, S. Weyers
Time and Frequency Department, Physikalisch-Technische Bundesanstalt, Braunschweig,
Germany
Email: Stefan.Weyers@ptb.de
The frequency shifting effect of Ramsey pulling3, which is caused by asymmetric hyperfine σ-transitions(F = 1, mF = ±1) in the Ramsey cavity, usually plays a minor role in the overall uncertainty budget offountain clocks. The reason is that due to the employed state selection technique most of the atoms are
in an mF = 0 clock ground state and the neighbouring mF ≠ 0 ground states are essentially emptied.
Moreover, the remaining mF ≠ 0 state populations are usually quite symmetrically distributed among the±mF states. However some peculiarities of fountain clocks can give reason for refreshed consideration.
Recently we have revisited frequency shifts in caesium fountains due to Ramsey pulling, boththeoretically and experimentally. Extending the work of Cutler et al.1, Zeeman ground state coherences
which are created before the first Ramsey interaction during the state selection process have been taken
into account in the calculations. The role of such initial Zeeman ground state coherences for Ramsey
pulling has been already investigated for thermal beam clocks, where the state selection is effectuated by
optical pumping4. Here we included initial Zeeman ground state coherences in a six-level density matrix
model to take into account the effects of the microwave pulse of the state selection process in a fountainclock. Solving numerically the von Neumann equation for this system we find similarly to the work of
Lee et al.2 that in the presence of initial coherences frequency shifts due to Ramsey pulling are largely
enhanced and can become significant under certain conditions. In contrast to the perturbative approachof previous work, the numerical approach enables us to take into account the phase variation of  of thetransverse rf cavity fields along the flight path of the atoms and to perform Monte Carlo simulations forrealistic atom cloud geometries and trajectories including cloud position offsets from the fountain axis.
We also experimentally explored the effects of Ramsey pulling in the PTB fountain CSF15. This
fountain is a suitable choice, because its state selection cavity is located just below the Ramsey cavity
within the magnetically shielded C-field region. Therefore the phases of the coherences created during
the state selection process do no average out and can result in detectable frequency shifts. For thegeneration of significant asymmetric coherent superpositions of the ground state components (F = 3, 0)and (F = 3, ±1), the microwave frequency in the state selection cavity was intentionally detuned from theclock transition frequency. Additionally, the excitation of hyperfine σ-transitions (F = ±1, mF = ±1)
was enhanced in both cavities by operating the state selection cavity at 9 and the Ramsey cavity at 7/2
microwave pulse areas. As a result, we observed frequency shifts up to ±310-14 at state selection
frequency detunings of ±120 Hz. For a range of detunings and magnetic field strengths in the cavity
region the observed frequency shifts match well the predictions of the model.

3

L. S. Cutler et al., Journal of Applied Physics 69, 2780 (1991)

4

H. S. Lee et al., Metrologia 40, 224 (2003)

5

S. Weyers et al., Metrologia 38, 343 (2001); S. Weyers et al., Proc. 6th SFSM, St. Andrews 2001, 64–71

IFCS-EFTF3-A1-3

Scattering of Cold Atom Coherences by Hot Atoms:
Background Gas Collision Shifts of Primary Fountain Clocks
Kurt Gibble1
1

Department of Physics, The Pennsylvania State University, University Park, PA, USA
Email: kgibble@psu.edu

Several primary cesium fountain frequency standards report an uncertainty of 1×1016 for the frequency
shift due to background gas collisions6-8. It contributes noticeably to a number of overall uncertainty
budgets, as low as 2.1×1016,8 and can be the largest single contribution in the uncertainty budget. These
uncertainties are estimated using the measured pressure shift for H2 in room-temperature Cs cell clocks9.
This is not justified since any momentum transferred to a cold atom almost always prevents it frombeing detected. We theoretically analyze the quantum scattering and show that H2 room-temperature
measurements produce frequency shifts with the opposite sign and overestimate the cold-atombackground-gas shift by an order of magnitude. Highly polarizable gases, including background Cs
vapor, produce similar shifts for cold atoms as H2. We also show that general considerations allow thebackground shift to bounded by measuring the loss in Ramsey fringe contrast due to background gas
collisions. Measuring the contrast or using the calculated shifts for cold atoms can significantly reducethe background gas shift in uncertainty budgets so that it no longer contributes significantly.

6

S. Weyers, U. Hübner, R. Schröder, “Uncertainty evaluation of the atomic caesium fountain CSF1 of the PTB,” Chr. Tamm,and A. Bauch, Metrologia vol. 38, p. 343-352, 2001.

7

R. Li, K. Gibble and K. Szymaniec, "Improved accuracy of the NPL-CsF2 primary frequency standard: evaluation of
distributed cavity phase and microwave lensing frequency shifts," Metrologia vol. 48, p. 283-289, 2011.

8

J. Guéna, M. Abgrall, D. Rovera, P. Laurent, B. Chupin, M. Lours, G. Santarelli, P. Rosenbusch, M. E. Tobar, R. Li, K.
Gibble, A. Clairon, and S. Bize, "Progress in Atomic Fountains at LNE-SYRTE," IEEE Trans. Ultrasonics,
Ferroelectrics, and Freq. Control, vol. 59, p. 391-410, 2012.

9

C. W. Beer and R. A. Bernheim, “Hyperfine pressure shift of 133Cs atoms in noble and molecular buffer gases,” Phys. Rev.
A vol. 13, p. 1052-1057, 1976.

IFCS-EFTF3-A1-4

Accuracy evaluation of IT CsF2
Filippo Levi1, Giovanni A. Costanzo2, Claudio E. Calosso1, Davide Calonico1,
Steven R. Jefferts3, Thomas P. Heavner3
1

2

Optic Division, INRIM, Torino, Italy
Electronic Department, Politecnico di Torino, Torino, Italy
3
Time and Frequency Division, NIST, Boulder, Co, USA
Email: f.levi@inrim.it

At INRIM we have realized and characterized a nitrogen cooled Cs fountain, the new Italian primary
frequency standard. Our fountain is the result of a fruitful collaboration with NIST Time and Frequency
Division, where the physical package of two twin fountains NIST F2 and ITCsF2 was realized.
The fountain accuracy was evaluated with respect to the following frequency shift: atom density,
blackbody radiation, Zeeman effect, gravitational potential, microwave leakage, distributed cavity phaseand other minor effects. Thanks to nitrogen cooling, low atomic density and particular care in thephysical structure design, we could reduce significantly important sources of uncertainty. The accuracy
budget of IT CsF2 combine to a total type B uncertainty of 1.8x10-16, and a similar statistical uncertainty
over a twenty day measurement evaluation (density shift is accounted for in the type A uncertainty).
Preliminary comparisons between ITCsF2, NIST F1 and NIST F2 have shown an agreement better than
5x10-16.
The most relevant contribution to the uncertainty budget are summarized in the following table.
ITCsF2 Accuracy Budget
Bias
Uncertainty
Effect(10-16)(10-16)
Blackbody Radiation-1.5
0.5
Zeeman Effect1103
1.0
Gavitation
261.2
0.1
Microwave-3.5
1.4
Total Type B
1.8
Atomic Density-3.2
2.1
Dead Time
1.2
Total Type A
2.4
Total
1356
3.0

IFCS-EFTF3-A1-5

Preliminary Results on the KRISS-F1 Primary Atomic
Fountain Frequency Standard
Sang Eon Park1, Myoung-Sun Heo1, Sang-Bum Lee1, Kurt Gibble2,
Yu1, Chang Yong Park1, Won-Kyu Lee1, Taeg Yong Kwon1

Dai-Hyuk

1

Division of Physical Metrology, Korea Research Institute of Standards and Science,
Daejeon 305-340, Korea
2
Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA
Email: parkse@kriss.re.kr
We present preliminary results of the primary fountainfrequency standard KRISS-F1. Figure 1 is a 3D drawing of
the KRISS-F1 physics package. Previously we have observedRamsey fringes with 133Cs atoms using a test interrogation
cavity. The linewidth of the central fringe was 1 Hz, and thesignal-to-noise ratio about 60010. With 133Cs and 87Rb
interrogation cavities, KRISS-F1 can be operated as a 133Cs
and 87Rb fountain11. Since the distributed cavity phase shifterror (DCP) gives one of the largest uncertainties of atomic
fountain primary frequency standards, new Cs and Rb cavities
that are designed to minimize DCP12 are about to be installed.
Our atomic sources are two 150 mg 133Cs and one 100 mg
87
Rb getters (Alvasource). With the getter sources we cancontrol atomic vapor pressure by adjusting getter currents,choosing to evaporate only the atom that we want to use.
We use two fiber port clusters (two-to-three) to distributecooling laser beams for Cs (852 nm) and Rb (780 nm) withsame splitting ratios. The outputs of fiber port clusters areconnected to fiber collimators with PM fibers. Six fiber
collimators are directly connected to the surfaces of trap
chamber ports to avoid beam misalignments. Each fiber
collimator contains monitor photodiodes. Of order 107 and
106 Cs atoms are trapped and cooled with MOT and opticalmolasses, respectively. An accuracy evaluation will be carried Fig. 1: 3D model of the KRISS-F1
out after installing the new cavities. Our conference paper physics package.
will update our progress towards the KRISS-F1 accuracy
evaluation.
10

S. E. Park, L. Z. Li, S.-B. Lee, D.-H. Yu, C. Y. Park, W.-K. Lee, T. Y. Kwon, "KRISS atomic fountain clock: Current
status," CPEM 2012 Conf. Digest, pp. 608-609, July 2012.
11

J. Guena, P. Rosenbusch, P. Laurent, M. Abgrall, D. Rovera, G. Santarelli, M.E. Tobar, S. Bize, A. Clairon,"Demonstration of a dual alkali Rb/Cs fountain clock," IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 57, no.3, pp.
647-653, 2010.
12

R. Li and K. Gibble, “Evaluating and minimizing distributed cavity pase errors in atomic clocks,” Metrologia, vol. 47, no.
5, pp. 534-551, 2010.

Opto-Electronic Oscillators
CLUB H
Monday, July 22 2013, 10:30 am - 12:00 pm
Chair:

Gilles Cibiel
CNES

IFCS-EFTF2-A2-1

Widely Tunable Opto-Electronic Oscillator
D. Eliyahu, W. Liang, E. Dale, A. Savchenkov,
V. Ilchenko, A. B. Matsko*, D. Seidel, and L. Maleki
OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA 91107, USA*Email: andrey.matsko@oewaves.com
We describe a novel photonic oscillator based on an optical whispering gallery mode (WGM)
microresonator. The oscillator features low phase noise (better than -100 dBc/Hz at 10 kHz), low power
consumption, compact size, and wideband tunability (1.6-15.6 GHz, limited by the bandwidth of the RF
amplifier). Performance parameters of the oscillator are superior to existing free running tunable
electronic oscillators and synthesizers operating in the frequency band, with the close-in phase noise atleast 10 dB lower than what is currently achieved. The oscillator is projected to have low acceleration
sensitivity. The successful fabrication of the device supports the development of novel ultra-wideband
receivers for communications and radar applications.
The oscillator takes advantage of the opto-electronic oscillator (OEO) architecture. The OEO is based on
an opto-electronic feedback loop that directly converts light energy to spectrally pure microwave or RF
oscillation, and has been described in detail in the literature. The oscillator is driven with a continuous
wave laser that acts as a source of energy. Additional RF amplification might be needed if the opticalpower is insufficient for the oscillation to start. An
important feature of the OEO architecture is that thephase noise does not degrade with increasing
oscillation frequency, in contrast to electronic based
oscillators.
The novel tunable OEO operates as follows. Light
from an agile tunable semiconductor laser is fed into a
broadband phase modulator, then to an ultra-high-Q
optical WGM microresonator, and then to a fast
photodiode, to produce an electric signal. A
comparably short fiber link (100-300 m or shorter) Fig. 2: Example of spectra of the RF signal
can be inserted at the front of the photodiode to generated by the tunable oscillator.
improve the phase noise of the oscillator. The signal
from the photodiode is amplified before being fed back to the phase modulator to complete the OEO
loop. Self-sustained oscillation starts when amplification in this feedback loop exceeds the loss. The
narrow optical bandwidth of the resonator (10 MHz) provides the filter function required for the loop.
The change in the laser frequency provides the tunability of the oscillator. The spectral purity depends
on the Q of the optical part of the circuit circuit ensured by the optical WGM microresonator. Thisconfiguration eliminates supermodes in the noise spectra associated with fiber OEOs.
The device does not require the laser light to pass through the ultra-high-Q optical resonator, as was
required in all previous implementations of resonator-based OEOs. Only one modulation sideband
passes the resonator mode. Aside from simplification of the architecture, this feature allows improving
the linearity of the optical part of the opto-electronic loop. Moreover, it allows reducing the resonatorsize leading to reduction of the vibration sensitivity of the system.

IFCS-EFTF2-A2-2

Kerr Frequency Comb-Based Ka-band RF Photonic Oscillator
V. Ilchenko, J. Byrd, A. Savchenkov, D. Eliyahu,
W. Liang, A. B. Matsko*, D. Seidel, and L. Maleki
OEwaves Inc., 465 North Halstead Street, Suite 140, Pasadena, CA 91107, USA*Email: andrey.matsko@oewaves.com
We report on the realization of a packaged RF photonic oscillator based on Kerr optical frequency comb
generated in an ultra-high Q crystalline whispering gallery mode (WGM) resonator. The oscillator
produces spectrally pure RF signals in Ka frequency band, characterized with single sideband phasenoise of -110 dBc/Hz at 10 kHz (see Fig. 1). The stability of the free running oscillator is characterizedwith Allan deviation of 10 -10 at 1s. We show that self-injection locking of the laser frequency to an
optical WGM is important for the stable operation of the device.
The optical Kerr frequency comb is a product of cubic optical nonlinearity of the material of which theresonator is made, and is generated by pumping one of the resonator modes with a continuous wave
coherent light. Kerr frequency comb generation is a unitary process, and can occur in a resonator where
the only losses are related to coupling to the external world. In such a case the repetition frequency ofthe comb does not depend on either frequency or
power of the pump light, and the comb becomes anideal oscillator that does not require any stabilization.
The phase noise of the repetition rate of such a comb
is given by Leeson formula with oscillator bandwidthcoinciding with the bandwidth of the optical modes of
the nonlinear resonator and the phase noise has only f2
and f0 spectral frequency components.
In practice, contact of the resonator with theenvironment as well as finite absorption in theresonator host material spoil the stability conditions,and the repetition rate of the comb becomes dependent
on parameters of the pump light. To regain thestability, locking the laser to the resonator mode
becomes necessary.
Fig. 3: Example of spectra of the RF signal

An important feature of the Kerr comb is that it isgenerated by the Kerr frequency comb-based RF
enough to stabilize only a single point in its frequency photonic oscillator (red line). The hump around 200
spectrum to obtain its stable operation. Since the kHz results from the noise of the x4 divider utilized
frequency of one comb line coincides with the to reduce the oscillation frequency to be able tofrequency of the pump laser, and the comb repetition measure it with OEwaves phase noise measurement
rate is fixed by the properties of the monolithic system. The theoretical curve for the phase noise ofresonator generating the comb, the entire Kerr comb is the particular oscillator is shown by blue dashedstabilized once the frequency of the pump laser is line.
stabilized to an external reference. There is no need togenerate an octave spanning Kerr comb to stabilize it. We discuss our progress in experimental
realization of the frequency stabilization scheme.

IFCS-EFTF2-A2-3

Fiber ring resonators with Q factors in excess of 1010
for Time and Frequency Applications
K. Saleh*, A. Fernandez*, O. Llopis*, Gilles Cibiel+* CNRS ; LAAS ; Université de Toulouse ; 7 av. du Colonel Roche, 31077 Toulouse, France+
CNES, 18 avenue Edouard Belin, F-31410 Toulouse, France
Email: llopis@laas.fr
Recent work has shown the capability of fiber ring resonators (FRRs) of featuring very high opticalquality factors (QOpt)13.These FRRs are compact and easy to use. However, their high quality factor,
combined with significant intra-cavity power enhancement factor, lead to the generation of nonlinear
optical effects inside the resonator, especially Rayleigh and Brillouin scattering. When the FRR is used
to stabilize the frequency of an optoelectronic oscillator (OEO), these nonlinear optical effects degrade
the OEO phase noise14. In order to eliminate a great part of these effects, an optical isolator has been
inserted inside a 100 m-long FRR that featured a QOpt of 2.1x109. The use of this FRR to stabilize thefrequency of a 10 GHz OEO has resulted in a phase noise level as low as -50 dBc/Hz at 10 Hz offset
frequency1. This result establishes the state-of-the-art phase noise level obtained in a passive opticalresonator based OEO.
-10RF IL= 15 dB

0
Since this aforementioned work, different studies
Δ = 15.4 kHz-20
have been performed to increase the FRR’s
quality factor above 1010. We have recently-40
measured an ultra-high QOpt of 1.25x1010 in a
-60
120 m-long FRR (see Fig. 1), but without an-80
isolator inside the fiber loop. When this FRR has
been included in the OEO setup, the use of a very-100
low optical power at the resonator’s input was-120
mandatory to prevent the nonlinear optical effects-140
from being generated efficiently. This has of
10
100
1 000
10 000100 000
1 000 000 10 000 000
Frequency (Hz)course degraded the noise to carrier ratio at theresonator output, resulting in an excess phase Fig. 4: Phase noise spectrum of a 10 GHz
based on a 120m-long FRR
noise of the OEO. Indeed, we have measured a optoelectronic oscillator
10
featuringa
1.25x10QOpt factor. The noise-40 dBc/Hz phase noise level at 10 Hz offset
measurement was performed at very low injected
frequency from a 10 GHz RF carrier (see Fig. 1)
optical power.
in spite of the ultra-high Q. Currently, we are designing a new 1 km-long immunized and optimized
FRR. This resonator will include a low loss isolator and the simulated QOpt is 1.5x1010. The use of thisBrillouin-immunized 1 km-long FRR in an OEO setup may lead to a much lower phase noise level thanthe one obtained with the 120 m-long FRR. Results on this new device will be presented at theconference.
-15

3dB

-25
-30
-35
-40

Rejection = 37 dB

S21 Magnitude (dB)

Phase noise (dBc/Hz)

-20

-45
-50

-55
10,1787

10,1792

10,1797

10,1802

10,1807

10,1812

10,1817Frequency (GHz)13

K. SALEH, P.H. MERRER, O. LLOPIS, and G. CIBIEL, “Optoelectronic oscillator based on fiber ring resonator: overallsystem optimization and phase noise reduction”, 2012 IEEE International Frequency Control Symposium (IFCS), 21-24 may
2012.
14

K. SALEH, O. LLOPIS, and G. CIBIEL, “Optical Scattering Induced Noise in Fiber Ring Resonators and Optoelectronic
Oscillators”, to be published in Journal of Lightwave Technology, (2013).

IFCS-EFTF2-A2-4

Experimental characterization of optoelectronic oscillators basedon optical mini-resonators
Rémi Henriet, Aurélien Coillet, Patrice Salzenstein, Khaldoun Saleh,
Larger, Yanne K. Chembo

Laurent

Franche Comté Electronique Mécanique Optique Thermique Sciences et Technologies (FEMTO-ST),
Centre National de la Recherche Scientifique (CNRS), Besançon, France
Email: patrice.salzenstein@femto-st.fr
We develop an optoelectronic resonator15 (OEO) based on intensity modulation and a high-Q disk
resonator. In this OEO, the resonant element is a 5 mm diameter crystalline whispering-gallery-mode
resonator16 (WGM). It selects the microwave oscillating frequency as an optical storage energy element.
This resonator also filters the microwave modulation signal. The generated oscillating frequency
corresponds to the free spectral range of the mini-resonator in the range 10–11 GHz17. Therefore nodelay-induced spurious peaks are present in the spectrum, in contrast to the case of the classicaloptoelectronic oscillator where the storage element consists of an optical fiber delay line18,19. This
resonator has a high quality factor which can be characterized by the cavity ring-down method20.
Another advantage of our system resides in its compactness allowing for efficient control of thetemperature. We present experimental results related to the temporal dynamics and phase noise
performance of WGM-based OEO. The analysis proceeds by matching the theoretical and experimental
results21. Power spectrum is given and the generated microwave signal stands 50 dB above the filterednoise of the RF amplifier. We evaluate the phase noise performance22 of this OEO, and also provide a
discussion relatively to its main features.

L. Maleki, "The optoelectronic oscillator," Nature Photonics, 5(12), 728–730 (2011).
V. S. Ilchenko, X. S. Yao, L. Maleki, "High-Q microsphere cavity for laser stabilization and optoelectronic
microwave oscillator," Proceedings of SPIE, 3611, 190–198 (1999).
K. Volyanskiy, P. Salzenstein, H. Tavernier, M. Pogurmirskiy, Y. K. Chembo, L. Larger, "Compact Optoelectronic
Microwave Oscillators using Ultra-High Q Whispering Gallery Mode Disk-Resonators and Phase Modulation," Optics
Express, 18(21), 22358–22363 (2010).
X. S. Yao, L. Maleki, "High frequency optical subcarrier generator," Electronics Letters, 30(18), 1525–1526 (1994).
K. Volyanskiy, J. Cussey, H. Tavernier, P. Salzenstein, G. Sauvage, L. Larger, E. Rubiola, "Applications of the
optical fiber to the generation and to the measurement of low-phase-noise microwave signals," J. Opt. Soc. Am. B, 25(12),2140-2150 (2008).
Y. Dumeige, S. Trebaol, L. Ghisa, Thi Kim Ngan Nguyen, H. Tavernier, P. Féron, "Determination of coupling
regime of high-Q resonators and optical gain of highly selective amplifiers," J. Opt. Soc. Am. B 25(12), 2073–2080 (2008).
Y. K. Chembo, K. Volyanskiy, L. Larger, E. Rubiola and P. Colet, "Determination of phase noise spectra in
optoelectronic microwave oscillators: a Langevin approach," IEEE J. of Quantum Electron., 45, 178–186 (2009).
P. Salzenstein, E. Pavlyuchenko, A. Hmima, N. Cholley, M. Zarubin, S. Galliou, Y. K. Chembo and L. Larger,"Estimation of the uncertainty for a phase noise optoelectronic metrology system", Physica Scripta, 2012(T149), 014025(2012).

IFCS-EFTF2-A2-5

High spectral purity microwave and terahertz oscillator
Gwennaël Danion1, Goulc’hen Loas1, Ludovic Frein1, Cyril Hamel1, Anthony Carré1, Steve Bouhier1,
Marc Vallet1, Marc Brunel1, Antoine Rolland1, Mehdi Alouini1, François Bondu1, Alain Brillet2, JeanPierre Coulon2, Frédéric Cleva2, Mourad Merzougui2, Alexandre Beck3, Guillaume Ducournau3, JeanFrançois Lampin3, Mohamed Zaknoune3, Christophe Coinon3, Xavier Wallart3, Emilien Peytavit3,
Tahsin Akalin3, Grégoire Pillet4, Loïc Morvan4, Ghaya Baili4 and Jérôme Bourderionnet4
1
Departement Optique et Photonique, IPR, Université Rennes1 CNRS, Rennes, France
2
ARTEMIS, Observatoire de la côte d’Azur, Nice, France
3
Groupe Photonique/THz, IEMN, Université de Lille CNRS,Villeuneuve d’Ascq, France
4
Thales Research and Technology, Palaiseau, France
Email: gwennael.danion@univ-rennes1.fr
We present a microwave/THz oscillator project (2012-2014) excepted to show below -150 dB rad2/Hz
phase noise at an offset frequency of 10 kHz for a 30 GHz carrier frequency as well as 18 GHz, 100
GHz, 400 GHz, 1 THz. The microwave/THz signal is obtained by mixing two optical frequencies with aphotomixer.
A dual-axis two frequency cross polarization laser will be stabilized onto two resonances of one FabryPerot cavity. The two frequencies sense the same cavity length fluctuations so that the best possible
relative stability of the beat note is limited by the relative dimensional stability of the cavity. This cavity
spacer is made with an ultra low expansion ceramic (ULE) placed in vacuum. A 75% fraction of thebeam transmitted by the cavity is used to stabilize the amplitude of the laser, and a 25% fraction is sent
on a polarizer and a photomixer for optical to millimetre wave conversion. The AM/PM conversion,
especially the opto-thermal conversion in the cavity i.e. the absorbed power fluctuations, is negligible ata 1 Hz frequency offset by stabilization of the
optical carrier at the 8.10-9/Hz1/2 level.
This oscillator is based on a dual frequency laser
system whose beat note frequency is continuously
tunable from DC to 600 GHz. An
Erbium/Ytterbium solid-state two-axis dualfrequency laser system followed by amplifier
stage has been developed. Each polarization
frequencies is independently tunable by 1.7 GHz
Fig. 5: One microwave/THz oscillator
steps by tilting its etalon and continuously with anelectro-optic crystal. We have chosen two lithium
tantalate (LiTaO3) crystals; thermo-optic(600MHz/°C) and electro-optic (1.1MHz/V) effects enable to lock each frequency on the resonance of a
1.5 GHz free spectral range Fabry Perot cavity. Each polarization light beam is amplified by a fiber
system. Our system amplifier is composed of an erbium doped fiber amplifier (EDFA) and asemiconductor optical amplifier (SOA) per polarization axis. This amplifier system permits to deliver 18
dBm power, to stabilize the power fluctuations and to reduce the relative intensity noise by 20 dB,
especially the relaxation oscillation.

IFCS-EFTF2-A2-6

Inverse Relationship between OEO Q-factor and g-sensitivity
James P. Cahill1,2, Justin Pritchett1, Ryan Sorensen1, Morris Berman1, Olukayode Okusaga1, Weimin
Zhou1, Gary M. Carter2, Curtis R. Menyuk2
1

2

U.S. Army Research Laboratory, Adelphi, MD
University of Maryland: Baltimore County, Baltimore, MD
Email: james.p.cahill.ctr@us.army.mil

We present evidence that the vibration (g-) sensitivity of a fiber-based OEO decreases as the fiber length
wound to a single spool increases. This is the result of two effects. First, the magnitude of the vibrationinduced perturbation remains constant with increasing fiber length because of diminishing mechanicalcoupling between the outer layers of fiber and the spool. Second, the power spectral density (PSD) of
the phase noise induced by a constant magnitude perturbation decreases as the Q factor (i.e. fiber length)of the cavity increases. This is an oscillator filtering effect. We can exploit these effects to constructfiber-based OEOs with lower g-sensitivity.
A sinusoidal vibration induces a peak in the OEO phase noise at the vibration frequency with PSD
proportional to ( ⁄ ) , whereis the vibration-induced change in length of the fiber delay, and is
the length of the total fiber delay.i We use this sideband to characterize both the filter effect and themechanical coupling between fiber and spool. In order to maintain consistency we use identical spools inall tests.

Figure 1. PSD of the vibration-induced phase noise peak
as a function of the length of fiber exposed to vibration.
Total OEO delay is fixed.
Figure 2. PSD of the vibration-induced phase noise peak
as a function of total OEO fiber delay length. The entire
delay is exposed to vibration.

To demonstrate the diminished coupling between fiber and spool, we keep the total fiber delay of the
OEO at a constant length while exposing only a portion,, of the fiber delay to a sinusoidal vibration.
Fig. 1 plots the PSD of the vibrational sideband as a function of. Because we hold all relevant
parameters constant, the PSD of the vibrational sideband will be proportional to. Yet fig. 1 showsthat the PSD is independent of. Thus, the mechanical coupling between the fiber and spool has
effectively saturated, and is independent of the fiber length.
To demonstrate the oscillator filtering effect, we expose the entire fiber delay of the OEO to a sinusoidal
vibration. Fig. 2 plots the PSD of the vibration-induced sideband as a function of the total delay length,. The PSD of the sideband decreases approximately quadratically as fiber length increases. Thus, as the
OEO Q increases, the vibrational noise is effectively filtered out.

Micro- Nano- Devices
CLUB D
Monday, July 22 2013, 10:30 am - 12:00 pm
Chair:

Ashwin Seshia
University of Cambridge

IFCS-EFTF4-A3-1

Nanoscale Resonant Sensors and Transducers with
1D and 2D Carbon Nanostructures
Max Zenghui Wang1
1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
Email: zenghui.wang@case.edu

Carbon-based nanostructures, such as graphene and carbon nanotubes, have outstanding mechanicalproperties and can be implemented as novel nanomechanical devices. Such devices, owing to theirminiature sizes and the unique physical properties of the materials, make excellent candidates forphysical and chemical sensors. In particular, nanomechanical resonators based on carbon nanotubes andgraphene have demonstrated exceptional sensitivities to various processes. On the other hand, theunique geometries of these miniature devices allow the mechanical motion of the carbon nanostructure
to be excited, detected, and tuned both optically and electrically, making them nanoscale mechanicaltransducers.

(c)

(a)
(b)

1.29

1.30

1/2

20

1/2

1/2

1.311.29
1.321.30
1.331.31
1.341.32

20
1.33

Frequency (MHz)Frequency (MHz)Fig. 6: Nanomechanical resonator devices based on 1D and 2D carbon
nanomaterials. (a) Enhanced illustration of Krypton atoms adsorbed ona single-walled carbon nanotube resonator, forming an atomic layer ofcommensurate solid. (b) Resonance frequency of a carbon resonator
decreases as background Kr pressure increases at 77K, revealing thecondensation of an adsorbed Kr layer on the nanotube surface. (c)Enhanced illustration of a doubly-clamped graphene resonator with local
gate electrode. (d) Thermomechanical resonance from a 1.315MHz
graphene resonator, and calibration of the noise floor and quality (Q)factor. Inset: SEM image of the device. Right axis shows scale indisplacement spectral density.

(pm/Hz )

1

40

1.34

Sx

40

1/2

2

60

(pm/Hz )

1/2

60

SV

SV
1

Krypton Gas Pressure p

3

Sx

2

(nV/Hz )

Q500

1/2

1/2

(nV/Hz )

(d)
3

1/2

f (MHz)In this paper, we will focus onthestate-of-the-art
nanomechanicalresonators
made of carbon nanotubes andgraphene, and evaluate theirpotential as ultra-sensitive
sensors and the ultimate limitson
theirsensitivities.
Specifically, we will describe
nanotuberesonator
mass
sensors with the best ones
achieving single-atom mass
sensitivity, a graphene resonantpenta-cene sensor, and ananotube resonant sensor forsurface processes such as
adsorption
and
phase
transitionii. In addition, we will
briefly discuss the ultimate
limits for these resonators forphysical sensing, identify the
key unresolved issues, andpropose the future possibilities
and directions of technicaleffortsiii.

IFCS-EFTF4-A3-2

NANOMECHANICAL MASS SPECTROMETRY FOR THE CHARACTERIZATION OF
HIGH MASS NANOPARTICLES
E. Sage1, A. Brenac2, R. Morel2, C. Dupré1, C. Marcoux1, H. Blanc1, M. S. Hanay3, S. Kelber3, M.L.
Roukes3, E. Colinet1, L. Duraffourg1 and S. Hentz1
1

CEA, LETI, MINATEC campus, 17 rue des martyrs, 38054 GRENOBLE Cedex 9, France.
2
INAC/SP2M and Université Joseph Fourier, CEA Grenoble, 38054 Grenoble, France.
3
Kavli Nanoscience Institute and Departments of Physics, Applied Physics, and Bioengineering,
California Institute of Technology, MC 149-33, Pasadena, California 91125 USA.
Email: eric.sage@cea.fr
Nano Electro Mechanical Systems (NEMS)-based Mass Spectrometry (MS) holds great promise forpoint of care applications23 or air quality monitoring. Real-time, single protein MS has recently been
demonstrated with top-down silicon resonators24. These devices operate in a mostly unexplored mass
range where particles display a wide mass distribution and where there is no mass standard. A directcomparison of NEMS-MS and reference MS measurement (here conventional Time-Of-Flight (TOF)
MS) is therefore crucial and is presented for the first time in this paper. The NEMS device is fabricatedon a 200mm SOI wafer with VLSI process. It is a 160nm thick doubly clamped beam, electrostaticallyactuated, with heterodyne piezoresistive detection25. Its first two resonance frequencies are
simultaneously tracked with Phase Locked Loops.
The NEMS device is inserted in the deposition chamber of acustom sputtering-gas aggregation setup able to produce
nanometric metallic clusters with tunable deposition rate anddiameter26 (see Figure 1). First the NEMS experimental mass
sensitivity is calculated by varying the deposition rate,measured with a Quartz Crystal Microbalance (QCM). In asecond step, tantalum clusters were projected onto the surface
Figure 1: Schematic of the mass deposition setupof the NEMS with a flux rate allowing for individual particle
measurement. Figure 2 shows preliminary mass distributions obtained with both NEMS-MS and TOFMS: the distribution shape is reproduced with fidelity (widths at half maximum 352kDa and 408kDa
respectively) and the mean masses are very close. NEMS-MS displays a resolving power similar to
TOF-MS in this mass range, and even better at higher mass
ranges. This demonstrates all the potential of NEMS-MS in
this mass range. The mass offset as well various mass
distributions are under investigation.

Figure 2: TOF-MS and NEMS-MS mass spectra oftantalum clusters. (1 Da=1.66 × 10-27 kg). Inset:
frequency jumps induced by individual landing
events.
23

A. Boisen, Nature Nanotechnology, vol. 4, pp. 404-405, 2009.

24

M. S. Hanay et al, Nature Nanotechnology, vol. 7, pp. 602-608, 2012.

25

E. Mile et al, Nanotechnology, vol. 21, pp. 165504, 2010.

26

R. Morel et al, Eur. Phys. J. D, 24, pp. 287-290, 2003.

IFCS-EFTF4-A3-3

Micro-electro-mechanical resonant tilt sensor with 250 nanoradian resolution
Xudong Zou, Pradyumna Thiruvenkatanathan and Ashwin A. Seshia
Nanoscience Centre, Department of Engineering, University of Cambridge, United Kingdom
Email: xz280@cam.ac.uk
This paper reports on a high-resolution frequency-output MEMS tilt sensor based on resonant sensing
principles1. The tilt sensor measures orientation by sensing the component of gravitational acceleration
along a specified input axis (Fig. 1). The devices consist of a suspended proof mass connected to two
double-ended tuning fork (DETF) resonators at each end through a lever arrangement. When subjected
to a tilt with respect to the gravitational axis, the tuning forks respond through a shift in their resonant
frequency and the differential frequency shift can be then calibrated with respect to the tilt angle.
Prototype devices are fabricated in a foundry SOI-MEMS process and optical micrographs of the device
are shown in Fig.2. The microfabricated chips are mounted onto standard chip carriers and then vacuum
packaged using a custom process. A combination of design enhancements enables significantly higher
sensitivity for this device as compared to previously reported prototype sensors1.
The vacuum packaged sensor chip is co-integrated with oscillator circuits on a PCB and mounted on amanual tilt table. Figure 3 depicts the tilt test set-up and Fig. 4 shows the output frequency variation of
DETF_1 (see Fig. 1) observed in a 0o-90o tilt test. The tilt test results indicate that the new sensor
provides a relatively linear response in the range of ±20o with a scale factor of approximately 50.06
Hz/degree. Fig. 5 shows the results of a measurement on the output stability of the device as determinedby Modified Allan Deviation measurements. The resolution of the resonant tilt sensor is found to beapproximately 250 nano-radian for an integration time of 0.8 s, which is over an order of magnitude
better than previously reported results27. The impact of polarization voltage induced noise and drift isalso seen by comparing the two plots in Fig. 5.
s
re s
mp s
Co tres
S

in
g*s

M pro
F≈

DETF_1q
Freq.1
Increaseensil
Te essStrofθ

Freq.2
Decrease

DETF_2Z
Tilt Axis

Fig.1: Tilt sensor operation principle. Fig.2: Optical micrograph of sensor (inset: vacuum packaged device).
DC Power
SourceFrequency
CounterManual Tilt
Table
Alkaline
Battery for
Device Bias

MEM Chip with Frequency
Tracking
VacuumOscillator on
Package
PCB

Fig.3: Experimental set- up.
27

Fig.4: Output response versus tilt angle.

Fig.5: Measured output stability.

X.Zou, et al., "Micro-electro-mechanical resonant tilt sensor," Frequency Control Symposium (FCS), 2012 IEEE International, 21-24 May 2012.

IFCS-EFTF4-A3-4

Two-Dimensional (2D) Semiconducting Crystal
Nanomechanical Resonators with Frequency Scaling
Jaesung Lee1*, Zenghui Wang1, Keliang He2, Jie Shan2, and Philip X.-L. Feng1*
1

Department of Electrical Engineering & Computer Science, 2Department of Physics
Case Western Reserve University, Cleveland, OH 44016, USA
Email: jaesung.lee@case.edu, philip.feng@case.edu

We report the first demonstration of resonant nanoelectromechanical systems (NEMS) based on
ultrathin molybdenum disulfide (MoS2) crystals down to only a few atomic layers, with measurementsof resonances in the HF/VHF bands, and studies of frequency scaling pathways toward the
UHF/microwave regimes. Atomically-thin 2D crystals have recently shown interesting promises forenabling new nanoelectronic and optoelectronic devicesiv. The unique mechanical properties of these2D crystals, including excellent elastic modulus (~0.21TPa) and extremely high strain limits (~102103
times higher than in 3D crystals), also make them attractive for 2D NEMS v,vi. Atomically-thin MoS2,
successfully isolated from the bulk only recently, is the first direct-bandgap semiconducting crystal in
2D form. The extensive measurements and analysis in this work with many devices establish MoS2 as a
new material for frequency-scalable NEMS resonators and transducers. Our study opens up possibilities
for new types of NEMS, where the mechanical properties of 2D MoS 2 can be coupled to its
semiconducting attributes.
Resonance Frequency (MHz)S1/2(V/Hz1/2)
V

We fabricate our devices
Number of Layers
(a)
(b)
using
mechanical1 2 3 4 5 10100
exfoliationand103 =Q = 500
m
0

.
5
5
N/m
characterize them with
0.
0.3
d=
opticalmicroscope,
0.1N
/m
SEM,
and
AFM.
m
102
2.5
0.2
Nanomechanicalmresonances
of
the
6
suspended MoS2 devices
are
0.1
101
detected with a sensitive
laser
interferometer. Figure 1ashows the characteristics
of a
0.7
7
70
17.5
18.0
18.5
typical device. We haveThickness (nm)Frequency (MHz)studied >20 devices with Fig. 1: (a) Thermomechanical resonance of a MoS2 Resonator. Insets:
diameters of d~1.5 to Device images from optical microscope (top left), SEM (top right), and~6m, and thicknesses AFM (bottom). (b) Calculated resonance frequency versus MoS2 thickness
t~10100
layers. for three different device diameters, each with 0.1 and 0.5N/m built-in
Combining data with tension. Dashed slopes indicate the plate and membrane limits. Horizontal
dashed line indicates the onset of VHF band. Measured resonancemodeling, we clearlyfrequencies from devices with different sizes are shown with different
identify the different symbols.
elastic regimes (Fig. 1b). The full paper will present our experiments in detail, including the fullanalysis with quantitative design rules and scaling laws for engineering UHF devices.

IFCS-EFTF4-A3-5

Aluminum Nitride Nano-Plate Resonant Infrared Sensor with
Self-Sustained CMOS Oscillator for Nano-Watts Range Power
Detection
Yu Hui and Matteo Rinaldi
Department of Electrical and Computer Engineering, Northeastern University, Boston, MA/USA
Email: hui.y@husky.neu.edu, rinaldi@ece.neu.edu
This paper presents, for the first time, a fast (thermal time constant of 1.3 ms) and sensitive(responsitivity of 267 Hz/µW) Infrared (IR) detector based on a MEMS-CMOS oscillator consisting ofan Aluminum Nitride (AlN) nano-plate resonator (NPR) connected to a compact and low power CMOS
self-sustained oscillator (fabricated in the AMIS 0.5 µm CMOS process) as a direct frequency readout.
A high performance (quality factor Q = 1433 and electromechanical coupling coefficient kt2 = 1.56%)
MEMS resonant structure based on a thin AlN (250 nm thick) NPR coated with Si3N4 (100 nm thick) as
IR absorber was fabricated and tested, showing a measured temperature coefficient of frequency (TCF)
of -30 ppm/K and FEM simulated temperature rise factor of 72.5 mK/µW. Thanks to the highelectromechanical performance of the MEMS resonator, a compact and low power (2.3 mW) selfsustained CMOS oscillator circuit was used as a direct frequency readout, enabling the demonstration of
a novel uncooled IR detector with a low Noise Equivalent Power (NEP) of 18 nW/Hz1/2.
High performance MEMS resonant IR detectors based on gallium nitride28 and Y-cut quartz29 have beenpreviously demonstrated, showing high sensitivity and low detection limit, however, none of them havebeen interfaced with CMOS readout circuits. This work takes the advantages of excellent piezoelectrictransduction and unique scaling properties of AlN (which, differently from gallium nitride and quartz,
can be deposited directly on silicon substrate with a low temperature sputtering process), enabling theuse of a self-sustained CMOS oscillator circuit, which drastically reduces the size, complexity, power
and noise performance of the frequency read-out and paves the way for the implementation of a newgeneration of NEMS uncooled, compact, fast, sensitive and low power IR focal plane arrays.

Figure 1: (a) The fabricated AlN nano-plate IR sensor connected to a self-sustained CMOS oscillator circuit for direct
frequency readout. (b) Measured Allan Deviation of the sensor output signal showing an ultra-low noise induced frequency
fluctuation of only ~28 ppb (3.5 Hz/122.6 MHz). (c) Sensor response for IR absorbed power of ~1 W. The inset shows the
AlN NPRs chip bonded to the CMOS readout chip fabricated in the AMIS 0.5 µm CMOS process.

28

V. J. Gokhale, J. Roberts, and M. Rais-Zadeh, Hilton Head 2012, pp. 46-49, 2012.

29

M. B. Pisani, K. L. Ren, P. Kao, and S. Tadigadapa, J. Microelectromech. Syst. Vol. 20, pp. 288, 2011.

Optical Fiber T+F Transfer I
CLUB E
Monday, July 22 2013, 02:00 pm - 03:30 pm
Chair:

Ronald Holzwarth
Menlo Systems

IFCS-EFTF5-B1-1

White Rabbit for Time Transfer
Erik van der Bij, Maciej Lipiński, Javier Serrano
CERN, Geneva, Switzerland
Email: Erik.van.der.Bij@cern.ch
White Rabbit30 (WR) is a protocol developed to synchronize nodes in a packet-based network with subns accuracy. The protocol results from the combination of IEEE1588-2008 (PTP) with two further
requirements: precise knowledge of the link delay and clock syntonization over the physical layer with
Synchronous Ethernet.
The master node in a WR link uses a clock derived from a reference (e.g, a 10 MHz from a Cs clock orGPS) to encode data over the physical layer, while the slave recovers this clock (syntonization) andbases its timekeeping on it. Absolute time synchronization between master and slave is achieved byadjusting the clock phase and offset of the slave to that of the master. The phase and offset adjustment isdone through the two-way exchange of PTP sync messages that are time-stamped to achieve sub-ns
accuracy thanks to dedicated hardware support.
In White Rabbit, the precise knowledge of the link delay is obtained by accurate hardware timestamps
and calculation of the delay asymmetry supported by knowledge of delays introduced by the hardware.
Multi-link WR networks can be made by chaining WR links forming a hierarchical topology of masterand slave nodes. The protocol allows the use of redundant links, thereby making the network morerobust to link failures.
Although originally specified to transfer timewith accuracy better than 1 ns on a network of
up to 2000 nodes over a distance up to 10 km,
tests show that better results and longer distances
can be obtained. Work is underway to integrate
the WR protocol into the next revisions of theIEEE1588 standard.
The complete electronics and firmware designsof WR interfaces and switches are publishedunder the CERN Open Hardware Licence;
therefore anyone can study the implementationand contribute to improve the performance andfunctionality. At the same time this hardware iscommercially available from engineering
companies who can provide support.

Fig.1: Measured offset and standard deviation
between the Pulse-Per-Second output of thereference switch (Master) and each of the threecascaded switches (Slaves 1, 2 and 3), connected
through 5 km of single mode fiber (total of 15 km
from the Master to the Slave 3 switch).

White Rabbit is currently being tested for
applications in control systems of particle accelerators, telescope arrays and for long distance accurate
time transfer.

30

White Rabbit. http://www.ohwr.org/projects/white-rabbit

IFCS-EFTF5-B1-2

Towards a Large-Scale, Optical Timing Distribution Systemwith Sub-Femtosecond Residual Timing Jitter
Michael Y. Peng1, Patrick T. Callahan1, Amir H. Nejadmalayeri1, Stefano Valente2,3, Kemal Ahmed2,
Ming Xin2, Eric Monberg4, Man Yan4, Lars Grüner-Nielsen4, John M. Fini4, Tony D. Roberts5,
Philip Battle5 and Franz X. Kärtner1,2
1

Department of EECS and Research Laboratory for Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA
2
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Hamburg, Germany
3
Department of Electrical Engineering and Computer Science, University of L'Aquila, L'Aquila, Italy
4
OFS Laboratories, Somerset, NJ, USA and 5AdvR, Inc., Bozeman, MT, USA
Email: mypeng@mit.edu

Over the past 10 years, we have developed a pulsed optical timing distribution system31 for large-scale,
long-term synchronization of radio-frequency and optical sources in X-ray laser facilities, which may extend
over several kilometers. The system consists of a femtosecond laser tightly locked to a microwave reference
and fiber links stabilized via compact, single-crystal balanced optical cross-correlators (BOCs). Sub-10-fs
performance over days of operation has been achieved32 but is limited mainly by polarization mode
dispersion in standard single-mode fiber. In the near future, it is necessary to improve timing distribution
down to sub-femtosecond precision; current facilities, such as LCLS at Stanford, can already produce X-ray
pulses shorter than 10 fs and concepts for sub-fs X-ray pulse generation are already in place. In the past two
years, we have developed key components and characterized commercial femtosecond lasers suitable forrealizing the next-generation, sub-femtosecond, fiber-based timing distribution system.
As demonstrated by Kim et al.33, BOCs can be used to characterize the timing jitter of mode locked
lasers with attosecond precision. We used this technique to characterize the jitter of two identical,
commercially-available femtosecond lasers (OneFive-ORIGAMI) and confirmed that their high-frequency
jitter for frequencies higher than 1 kHz is less than 70 as (Fig.1a). These lasers therefore have sufficiently
low noise to serve as master oscillators for sub-fs timing distribution. Second, to eliminate slow drifts
induced by polarization mode dispersion, we implemented a 1.2-km polarization-maintaining fiber link using
1 km of standard PM fiber and 0.2 km of novel dispersion-compensating PM fiber from OFS. Link operationfor 16 days showed only 0.9 fs RMS timing drift and during a 3-day interval only 0.2 fs drift (Fig.1b). Lastly,
we present a hybrid integrated BOC fabricated by AdvR using PPKTP waveguides34 (Fig.1c). We seek tosolve long-term drift issues by eliminating alignment drifts in free-space BOCs and to reduce the required
optical power by a factor of 10-100 while achieving similar signal-to-noise levels as those from bulk-crystal
BOCs. With further development, these components can soon be interfaced to realize a completely fibercoupled, sub-femtosecond optical timing distribution system.

Figure 1. (a) Optical-to-optical synchronization of two femtosecond lasers with an integrated timing jitter of 67 as for frequencies above 1 kHz; (b) 1.2-km
timing-stabilized PM fiber link with uninterrupted operation for 16 days with ~0.9 fs RMS timing drift and 3 days with ~0.2 fs drift; (c) Effective timing
sensitivity curve for an integrated PPKTP waveguide operated as a double-pass, balanced optical correlator.

J. Kim et al., “Drift-free femtosecond timing synchronization of remote optical and microwave sources,” Nature Photon., 2: 12, 733–736, 2008.
M. Ferianis et al., "All-optical Femtosecond Timing System for the Fermi@ Elettra FEL," Proc. FEL., Vol 11, 2011.
J. Kim et al., “Attosecond-resolution timing jitter characterization of free-running mode-locked lasers,” Opt. Lett., 32: 24, 3519–3521, 2007.
34
A. Nejadmalayeri et al., “Guided wave optics in periodically poled KTP,” Opt. Lett., 34, 2522-2524, 2009.
31
32
33

IFCS-EFTF5-B1-3

Local ties control in application of laser time transfer
Jan Kodet, Ulrich Schreiber, Johann Eckl#, Ivan Prochazka*, Petr Panek+
Technische Universität München, Wettzell Observatory, 93444 Bad Koetzting, Germany
Bundesamt für Kartographie und Geodäsie, Geodätisches Observatorium Wettzell, Germany*Czech Technical University in Prague, Brehova 7, 115 19 Prague 1, Czech Republic+
Institute of Photonics and Electronics, Chaberska 57, 182 51, Prague, Czech Republic#kodet@fs.wettzell.de

In many fundamental physical experiments time plays an important role. The standard way for thecomparison of time and frequency is the application of GNSS signals and the Two-Way Satellite Timeand Frequency Transfer - TWSTFT. This technique is based on radiofrequency signal transmission.
Recently, there is a rapid increase of optical time comparison development, which uses the Satellite
Laser Ranging network (SLR). Currently the French project T2L2 is in operation on board Jason 2 andthe European Space Agency project ELT in support of the Atomic Clock Ensemble in Space (ACES) is
under development. The goal of both projects is the time synchronization with a precision below 40 ps
rms and an absolute error well below 100 ps. Comparing the results of the optical time transfer with the
GNSS time comparison requires unprecedented control of the local ties between the different
observation techniques. One of the possible methods is the application of the Two Way Time Transfer(TWTT) on a single coaxial cable. Such a system can be implemented using two or more event timers,
which are interconnected by a standard coaxial cable. The event timers are exchanging pulses between
each other and time tagging them. Out of the measured result one can evaluate the difference of timescale represented by the event timers. It was shown that such a technique can be used for time transfer
with a precision of a few picoseconds of rms and an absolute error below 20 ps for distances reaching
several hundreds of meters.
We have implemented this technique for establishing and monitoring the absolute time delays between
the SLR system and the time laboratory on the Geodetic Observatory in Wettzell. The event timers weredeveloped at the Czech Technical University. The measurement principal is based on a SAW filter
excitation. The Event Timers were located in different buildings 50 meters apart and with the help of the
TWTT technique, the delay between them was measured. The second input sockets of the event timers
were used to monitor the respective local timescale.

IFCS-EFTF5-B1-4

Single Photons Optical Two Way Time Transfer
Providing Picosecond Accuracy
Ivan Prochazka1, Josef Blazej1, Jan Kodet1,2, Petr Panek3
1

Czech Technical University in Prague, Brehova 7, 115 19 Prague, Czech Republic2
Technical University Munich, Station Wettzell, 93444 Koetzting, Germany
3Institute of Photonics and Electronics, ASCR, Chaberska 57, 182 51 Prague, Czech Rep.
Email: prochazk@cesnet.cz
We are reporting on a new approach to an optical Two Way Time Transfer (TWTT) which is based on
optical signals of individual photons. This approach enables to reach extreme timing stabilities andminimal systematic errors using existing electro-optic technologies.
The two way time transfer is an effective way to synchronize two independent time scales with highprecision and accuracy independently on the variations of the interconnecting channel35. In our previous
work we have demonstrated electronic circuits for two-way time transfer via a single coaxial cable withpicosecond accuracy and precision36. This technique may be effectively applied in conﬁgurations, where
the sites may be interconnected by a broad bandwidth coaxial cable. Considering the performance of the
top quality coaxial cables available, the picosecond performance may be accomplished over distances up
to 2 km maximum. For longer distances the optical approach may be considered.
We have designed and tested the optical analogy of the two way time transfer using a common opticalchannel. To minimize the systematic error sources the photon counting approach has been applied. The
pilot experiment has been completed in our lab. The test pulses were generated by laser diodes in a formof short pulses. The signal may be propagated either in a single mode optical ﬁber or in a free space.
Thanks to photon counting approach the optical loses on the line is not a critical issue, one way losses of
90 dB may be tolerated. The optical signals are detected by solid state photon counters, the timing isaccomplished by sub-ps timing systems NPET37. The experiment proved the capability of this techniqueto maintain picosecond stability of TWTT over the periods of seconds to days. The systematic errors are
expected to be of the order of units of picoseconds. The experiment results will be presented.

35

J. Levine, “A review of time and frequency transfer methods,” Metrologia, vol. 45, p. S162 - S174, 2008.
I. Prochazka, J.Kodet, and P.Panek, “Electronic circuit for two-way time transfer via a single coaxial cable withpicosecond accuracy and precision,” Rev. of Sci. Instruments, vol 83 (11), 116104, 2012.
37
I. Prochazka, J. Blazej, J. Kodet, “New technologies for time transfer with picoseconds precision and accuracy,” In2012 International Frequency Control Symposium Proceedings, Baltimore, MD, USA, 2012 IEEE International, pp. 298 304, May 21 - 24 2012, doi: 10.1109/FCS.2012.6243610
36

IFCS-EFTF5-B1-5

Implementing a nationwide robust time- and frequency
distribution
Per Olof Hedekvist, Sven-Christian Ebenhag, Carsten Rieck, Kenneth Jaldehag1, Jonatan Walck, Patrik
Fältström2, Peter Löthberg3,Ove Landberg, Håkan Swedenborg4
1

SP Technical Research Institute of Sweden, Borås, Sweden
2
Netnod Internet Exchange, Stockholm, Sweden
3
Stupi, Los Altos, CA/USA
4
PTS, Swedish Post and Telecom Agency, Stockholm, Sweden
Email: per.olof.hedekvist@sp.se
There is an increasing need for accurate and reliable time information in digital communication,
including network timing, data time stamping, smart grid surveillance and control, cyber forensics, etc.
The efforts have to a wide extent being focused on accuracy, precision and authentication, to assure thatthe given time and frequency signals are accurate and reliable. In addition to this, the implementation in
Sweden has worked on the robustness of the time keeping, and the access to reliable signals from a
network of spatially distributed redundant clock sites.
The Swedish UTC-realization, UTC(SP), is managed by SP, the National Metrology Institute of
Sweden, and located in Borås in the SW part of Sweden. UTC(SP) is based on an H-maser corrected toan ensemble of atomic clocks located in their own facilities, and at two other locations. In the new
distributed system, two redundant timescales are also implemented at a new location in Stockholm. Eachof these timescales will be based on an H-maser, and constantly managed and adjusted using the datafrom all other available atomic clocks in the network as well as the UTC-data from SP. If any of theclocks are disconnected, each timescale will automatically make a best estimate based on the data fromthe remaining clocks. In addition, 4 distribution
points operated by Netnod in Stockholm,
Gothenburg, Malmo and Sundsvall will be
upgraded with two Cs clocks at each site, also
reporting data for the time scales. Each
distribution point is right at the Internet
exchanges, synchronized to UTC(SP) using timetransfer links, and offers 2 independent NTPservers to the general public adding robustness tothe time system at large and bringing timesynchronization services closer to the Internet
community.
The time is made available to network users
through NTP, both IPv4 and IPv6, and one server
implemented for the distribution of authenticatedntp. Furthermore, the access to stable E1
frequency is offered at the Netnod locations, andthe SP sites can be used as references for GNSS
time transfer. The time and frequency data, Fig. 7: National distribution of atomic clocks, for a
including uncertainties and accessibility, is robust access to reliable time and frequency signals
logged and published online for free evaluation.

Micro-Scale Oscillators
CLUB D
Monday, July 22 2013, 02:00 pm - 03:30 pm
Chair:Dan Stevens
Consultant

IFCS-EFTF1-B2-1

UHF Quartz MEMS Oscillators for Dynamics-Based System Enhancements
R.L. Kubena, D.J. Kirby, Yook-Kong Yong*, D.T. Chang, F.P. Stratton, H.D. Nguyen, R.J. Joyce, R. Perahia, H.P Moyer, &R.G. Nagele
HRL Laboratories, LLC, Malibu, CA., 90265 USA*Rutgers Univ., Piscataway, New Jersey
Email: rlkubena@hrl.com
Processes for fabricating full wafers of UHF quartz MEMS oscillators bonded to Si have been developed at HRL over the
past several years. These devices have shown state-of-the-art noise and stability38 along with extremely small vacuum
packaged die size of less than 3 mm2. An interesting by-product of the high frequency, small size, and wafer-scale fabricationof these devices is that several novel dynamics-based enhancements can be considered. These include the reduction of thephase noise contributions of the amplifier by driving the resonator into a non-linear state with a high phase slope versus
frequency.39,40 In addition, large enhancements of the Q through nonlinear modal coupling of the fundamental and third
overtone have been predicted.41 By adding control electrodes on the Si substrate and in the capping wafer and capacitiveelectrodes on the quartz, dynamic force rebalancing can be utilized to reduce the vibration sensitivity using low voltages.
Finally, co-integration of these devices with other sensors on a chip, such as a microgyro, becomes possible and allows active
frequency-locking schemes to be implemented in a small ovenized housing for improved inertial bias stability. These features
may provide important performance enhancements for future mobile communication systems.
An example of the phase noise enhancements that are possible with these techniques is shown in Fig. 1. An 804-MHz
fundamental-mode AT-cut oscillator circuit was configured with a variable gain amplifier, phase shifter, and admittancemeasurement probes to allow sweeping the phase (frequency) across the resonator at different known applied AC voltages.
As the drive level approaches the bifurcation point (>150 mV), a sharp drop in the phase noise is observed near the highest
phase slope. We believe this is the first time such a
sharp drop in phase noise has been observed near thecritical point for nonlinearly operated quartz oscillators.
For 200 mV of applied voltage, the true phase noise
reduction was masked due to limited gain from theamplifier in the loop. For automated start-up, a phasedither in the loop in conjunction with an AGC circuit
can be used to adjust the operating point for locating thehighest phase slope conditions. Since the quartz plate is
only about 2-µm thick, the required voltages forbifurcation are within CMOS levels.
COMSOL models have been developed to enable themodeling of stress propagation from the mounts into theactive resonator and the effect on the f/T curves.
Fig.1. Phase Noise versus operating frequency orControlling and minimizing these stresses in small
phase versus drive voltage for an 804-MHz AT-cut
quartz resonators is critical for maintaining high stability oscillator.
while concurrently implementing these new concepts. In this paper, we will review these concepts and describe our recent
modeling and experimental work for implementing them.

38

R.L. Kubena, et. al., “Next Generation Quartz Oscillators and Filters for VHF-UHF Systems,” Proc. 2006 IEEE
International Microwave Symposium, San Francisco, Ca., June 11-16, 2006.
39

B. Yurke, et. al., “ Theory of amplifier-noise evasion in an oscillator employing a nonlinear resonator,” Phys. Rev. A, vol.
51, no. 5, pp. 4211-4229, May 1995.
40

H.P. Moyer, et. al., “Nonlinear Behavior of an UHF Quartz Resonator in an Oscillating System,” 2012 IEEE IFCS, May
21-24, 2012.
41

Yook-Kong Yong, “Resonator Q Increase and Noise Reduction in Third Overtone Thickness Shear Resonators by the
Nonlinear Characteristics of their Fundamental Thickness Shear Mode,” Proc. 2012 IEEE IFCS, May 21-24, 2012.

IFCS-EFTF1-B2-2

Nonlinear Dynamics in Aluminum Nitride Contour-ModeResonators
Nicholas Miller, Gianluca Piazza
Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh,
Pennsylvania, USA
Email: njmiller@andrew.cmu.edu
Aluminum nitride (AlN) contour-mode resonators (CMRs), see figure 1 right, have previously beenshown to exhibit a softening nonlinearity due to self-heating1,2. In previous analysis2 the resonator wasmodeled quasi-statically leading to a Duffing resonator model. In this work we show that the slow
dynamics of the resonator amplitude and phase are described by the model
̇

(

)

(

)
̇

| |

where u is the resonator’s normalized complex amplitude and τ is the normalized resonator temperaturedeviation from ambient. The resonator admittance, Y, is a linear function of u. The fixed points( ̇̇) of this model agree with that of the Duffing resonator model with nonlinear damping.
However, the dynamics differ due to thermal relaxation over the time scale γ. This is typically in the
millisecond range for AlN CMRs. Accordingly, the difference between the self-heating model and theDuffing model can be revealed during fast frequency sweeps using a vector network analyzer, see figure
1 left. This has important ramifications for applications of resonator nonlinearity, for example theevasion of amplifier noise in oscillators3.

Comment [GP1]: Fix label on Y axis of first plot
as you have Y^2…(it should be Y).
Any chance we could make the lines a bit thicker orsomehow more easily viewable?
The definition of fixed points is not very clear….what
exactly do you mean in this case?
Finally, how about sticking in an SEM of theresonator?...just in case some reviewer only look at
the title and figure.
Comment [GP2]: Maybe add a reference here…

Fig. 8: (Left) Admittance, Y, and temperature, τ, response to a frequency sweep. The model prediction
is shown with solid curves and the measured sweeps up and down with markers. The black dashedline shows the fixed points of the above resonator model. (Right) Microscope image of AlN CMR.
1

A. Tazzoli et al., “Experimental investigation of thermally induced nonlinearities in aluminum nitride contour-mode mems
resonators.” IEEE Electron Device Letters, vol. 33, p.724-726, 2012.
2
3

J. Segovia-Fernandez and G. Piazza, “Thermal nonlinearities in AlN contour mode resonators”, in review, 2013.

L.G. Villanueva et al., “Surpassing fundamental limits of oscillator using nonlinear resonators”, arXiv:1210.8075[condmat.mes-hall], 2012.

IFCS-EFTF1-B2-3

Close-in Phase Noise Reduction in an Oscillator based on 222
MHz Non-Linear Contour Mode AlN Resonators
J. Segovia-Fernandez, C. Cassella, G. Piazza
Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
Email: jsegovia@andrew.cmu.edu
Phase Noise (PN) reduction in oscillators has been traditionally accomplished by using low noise
amplifiers or high quality factor (Q) resonators, in accordance with Lesson theory42. However, previous
work on nonlinearly driven resonators has suggested that locking the device into a particular nonlinear
state (so-called bifurcation) can help evading the amplifier noise43. AlN Contour Mode Resonators(CMRs) are an emerging class of piezoelectric MEMS devices exhibiting high Q and low motional
resistance at high frequencies (fres). Because of their micron-scale size the AlN CMRs have revealed anonlinear behavior induced by self-heating when driven with relatively high power44. In this work, weshow a substantial improvement of the PN close-in (-20dBc/Hz @ 100Hz) of a 222 MHz oscillator thatincorporates a nonlinearly driven AlN CMR.
The oscillator circuit presented here was built using coaxial electronic components (Fig. 1). The
experiments were carried out by setting the DC bias of the amplifier to 6V, therefore ensuring enoughgain to both sustain oscillations and drive the resonator nonlinearly. The phase shifter was manually
tuned in steps of 5° to increase the circuit delay and, hence, lock the oscillator at different frequencies(fosc) on the non-linear resonance curve of the 222 MHz AlN CMR device. Fig. 2 depicts PN (dBc/Hz)
versus offset frequency (foff) for different phase delays. A dramatic change of slope in the PN close-in(foff<1kHz) is observed when fosc<fres (fres is indicated on the plot). This frequency corresponds to thedevice operating past bifurcation, as we can infer by measuring the resonator admittance in open loop
for the same output power. The data highlight that for particular phase shifts >15°, the PN curve
experiences a significant reduction in slope (from 1/f4 to 1/f2). Furthermore, the experimental results
show that the AlN CMR thermal time constant (τTH)3 limits the maximum foff for which a PN
improvement can be recorded.

42

Fig. 9: SEM of the 222MHz AlN CMR; b)
wirebonded AlN CMR on a PCB; andboth c) schematics and d) actual oscillator
setup including (1) AlN CMR, (2) Fig. 10: a) PN vs foff at DC bias=6V and different phase
amplifier, (3) power splitter, and (4) phase shifts (q). b) Open loop amplitude and phase of AlN CMR
admittance for various input powers.
shifter.

D. B. Leeson, “A simple model of feedback oscillator noises spectrum,” Proc. IEEE, vol. 54, pp. 329–330, 1966.
B. Yurke, D.S. Greywall, A.N. Pargellis, and P.A Busch, “Theory of amplifier-noise evasion in an oscillator employing anonlinear resonator,” Phys. Rev. A, vol. 51, pp. 4211-4229, 1995.
44
J. Segovia-Fernandez, A. Tazzoli, M. Rinaldi, G. Piazza, "Nonlinear lumped electrical model for contour mode AlN
resonators," IEEE Int. Ultrasonics Symp., pp.1846-1849, 201143

IFCS-EFTF1-B2-4

MEMS-based mechanical AGC for oscillator circuits
Andreja Erbes1, Xueyong Wei2, Ashwin A. Seshia1
1

Engineering Department, University of Cambridge, Cambridge, United Kingdom
2
School of Mechanical Engineering, Xi'An Jiaotong University, Xi'An, China
Email: ae279@cam.ac.uk

This paper investigates a nonlinear amplitude saturation behavior in an electrostatically transduced, Si
MEMS disk resonator (Fig. 1), operating in its secondary elliptical bulk-mode (2EBM) at 3.932 MHz
towards its implementation as an all-mechanical automatic gain control (AGC) element. The nonlinear
vibration behavior of the 2EBM mode is experimentally observed in open-loop testing (Fig. 2) such thatabove a threshold small signal drive vac = 1.22 Vp-p at a polarization voltage of VDC = 100 V, thevibration amplitude of the mode saturates. Such nonlinear clamping behaviors have been reported inother MEMS resonators45, 46.We also study this nonlinearity in an oscillator circuit (Fig. 3) designed
such that the driving power level at the resonator input (vac) is manually tuned as the circuit operates andthe oscillation amplitude is recorded (voutput), for different VDC. Fig. 4 shows a clear transition of theoscillator amplitude from the linear to the nonlinear saturation region as the driving power increases.
This transition point is consistent with the behavior measured in open-loop testing. Short-term frequency
stability measurements were also conducted for different vac and the resulting Allan deviation plots (Fig.
5) show an improvement in the short-term stability (0.5s averaging time) from 1.4 ppb in the linear
region (vac = 1.2 Vp-p) to 0.4 ppb for operation in the amplitude saturation region (vac = 1.6-2.4 Vp-p).
These results indicate that the amplitude clamping effect in nonlinear microresonators can be applied in
MEMS based oscillator circuits as a mechanical AGC to simplify the circuit configuration as well as
retain excellent short term frequency stability.

Fig. 1: Optical micrograph ofthe 3.932 MHz disk resonatorFig. 2: Measured S21 parameter at the 2EBM
mode for different drive vac and VDC=100 V.

Fig. 4: Oscillation amplitude voutput for different drive
vac in the closed loop configuration of Fig. 3.

45

Fig. 3: Schematic of theoscillator circuit using thedisk resonatorFig. 5: Allan deviation plots for different drive vac and
VDC=120V.

C. van der Avoort et al., “Amplitude saturation of MEMS resonators explained by autoparametric resonance”, J.
Micromech. Microeng., vol. 20, no. 10, 2010.
46
L. Lipiäinen et al., “Nonlinear excitation of a rotational mode in a piezoelectrically excited square-extensional mode
resonator”, Appl. Physics Lett., vol. 100, no. 153508, 2010.

IFCS-EFTF1-B2-5

A 1 GHz SAW oscillator on epitaxial GaN/Si substrate: toward cointegrated frequency sources
Marc Faucher1, Gilles Martin2, Jean-Michel Friedt2, Sylvain Ballandras3,4
1
2

IEMN UMR CNRS 8520, Villeneuve d'Ascq, France

FEMTO-ST, UMR 6174 CNRS-UFC-ENSMM-UTBM, Besançon France
3

SENSeOR SAS, TEMIS Innovation, Besançon France4

frec|n|sys SAS, Besançon France

Email: marc.faucher@iemn.univ-lille1.fr
Motivation :SAW-resonator based oscillators are fabricated for embedded applications such as Radar and local
oscillator for space missions requiring frequency transposition for telecommunications. Although rather
compact, these discrete devices contribute to on-board charge and are currently poorly suited to cointegration. The possibility for providing ultimately compact sources able to operate on the same board
than most radio-frequency circuits would yield a major advance for integrated time-frequency systems.
Achieved work :We investigated the use of GaN/Si(111) epilayers for fabrication of SAW oscillators. Devices have been
designed on 1.8µm thick GaN. Tank to the analysis of the obtained results, a set of elastic constants has
been fitted. Comparison between experimental and theoretical transfer functions has been also exploited
to refine the estimation of the wave characteristics. An oscillator has been finally built using theobtained resonators to assess the interest of this material for this kind of application.
Results:
SAW resonators have been processed using E-beam lithography with a 2 µm period, yielding resonators
operating near 1 GHz with Q factor close to 2000 and insertion losses better than 12 dB. Two port
resonators were inserted in a feed-back loop oscillator based on a low-noise HX2400 amplifier, enabling
short term measurements as well as phase noise extraction. A short term stability of 10-7 per second has
been measured, clearly penalized by the temperature sensitivity of the SAW (near -30 ppm.K-1). A phasenoise figure of -115 dBc/Hz was found at 10 kHz from the carrier and a flour of -165 dBc/Hz was finallymeasured (Fig. 1). Although these figures are not the best achievable using this material, they are reallypromising as High Electron Mobility Transistors (HEMTs) are currently manufactured on the same
substrate, allowing for future development of co-integrated SAW oscillators.

Fig. 11: Measured response of the GaN resonator (left) and phase noise measurement (right)

Lattice Clocks I
CLUB H
Monday, July 22 2013, 02:00 pm - 03:30 pm
Chair:

Tetsuya Ido
NICTIFCS-EFTF6-B3-1

Strontium lattice clocks with reduced BBR uncertainty
Stephan Falke, Nathan Lemke, Stefan Vogt, Uwe Sterr, Christian Lisdat
Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany
Email: stephan.falke@ptb.de
The leading contribution to the uncertainty of state-of-the-art optical lattice clocks is related to theblackbody radiation (BBR) emitted by the surfaces surrounding the atoms that are interrogated while
being held in an optical lattice. In strontium and ytterbium optical lattice clocks relative frequency
corrections of several 10-15 are applied to account for an ac Stark frequency shift due to the BBR of theapparatus at room temperature. Its uncertainty causes the leading contribution to the uncertainty budgetof the clock of a few times 10-17.
Both, the environmental temperature and the correction coefficient need to be known precisely to reduce
this uncertainty contribution. We will present work that improved significantly the knowledge of thecorrection coefficient for strontium lattice clocks. We measured the differential dc polarizabilty of theclock states to a high precision. This quantity was used along with other available data, such as themagic wavelength or oscillator strengths of atomic transitions, to model the ac polarizability of the clockstates. It is then possible to integrate the ac Stark shift of the clock transition over the temperaturedependent BBR spectrum. We used Monte-Carlo simulations to determine the uncertainty of thecorrection.47 (See related work on ytterbium.48) Now, the uncertainty of the BBR correction coefficient
limits the uncertainty at room temperature to a few 10-18 fractional frequency uncertainty. Absolutetemperature measurements of the environment of better than 0.05 K will be required at room
temperature to fully exploit the improved correction coefficient. At present, despite a reduction ofthermal gradients across our vacuum chamber, the associated temperature uncertainty of 0.4 K translates
to an uncertainty due to blackbody radiation of 3×10-17.
To target sub-10-17 relative frequency uncertainty with optical lattice clocks, the design of the setup mustallow for a precise description of the BBR field. We follow two approaches:(a) a more homogeneous temperature of the vacuum chamber and(b) shuttling the atoms into an environment providing a cryogenic blackbody radiation field.49
With the improved blackbody radiation correction the systematic uncertainty of lattice clocks is alreadysignificantly below even the best cesium fountain clocks. Moreover, their instabilities are typicallyorders of magnitude below those of microwave clocks.50 Direct comparisons between two or more
optical clocks are becoming the method of choice. At PTB the strontium optical lattice clock is
compared to an ytterbium single ion clock51 for studies of systematic frequency shifts and direct
frequency ratio measurements evaluating the clocks with respect to a possible re-definition of theSecond.

47

T. Middelmann et al., Phys. Rev. Lett. 109, 263004 (2012).

48

J. Sherman et al., Phys. Rev. Lett. 108, 153002 (2012), K. Beloy et al., Phys. Rev A 86, 051404 (2012).

49

T. Middelmann et al., IEEE Trans. Instrum. Meas. 60, 2550 (2011), T. Middelmann et al.,New. J. Phys. 14 073020 (2012).

50

C. Hagemann, IEEE Trans. Instrum. Meas., DOI: 10.1109/TIM.2013.2242597 (2013).

51

N. Huntemann et al., Phys. Rev. Lett. 108, 090801 (2011).

IFCS-EFTF6-B3-2

Characterizing the blackbody shift in a lattice clock to 1x10-18
A. D. Ludlow1, K. Beloy1, J. A. Sherman1, N. Hinkley1,2,
N. Phillips1, N. D. Lemke1, M. Schioppo1, C. W. Oates1
1Time & Frequency Division, National Institute of Standards and Technology,
Boulder, Colorado USA
2
Department of Physics, University of Colorado, Boulder, Colorado USA
Email: ludlow@boulder.nist.gov

The optical lattice clock promises frequency uncertainty and instability at fractional levels of
10-18. To achieve such performance, several key advances are first required and research with this focus
is being undertaken worldwide. Perhaps the most formidable obstacle to be overcome is controlling theblackbody radiation (BBR) shift at the 10-18 level.
Characterization of the BBR shift first requires accurate knowledge of the atomic sensitivity to thermalradiation, rooted in the details of the electronic structure. Because of the low-frequency nature of roomtemperature blackbody emission, this atomic sensitivity can be neatly divided into two terms: the static
polarizability and a small dynamic correction accounting for time-dependent aspects of the thermalradiation field with the corresponding atomic response. We report a high accuracy measurement of thedifferential static polarizability of the clock transition in a Yb lattice clock, yielding an uncertainty in thestatic atomic sensitivity which corresponds to < 1x10-19 clock uncertainty52. Furthermore, we report two
independent determinations of the dynamic correction53, which consequently contributes to a BBR shiftuncertainty of 1x10-18 at room temperature.
To realize a total BBR shift uncertainty at such a level, the thermal radiation environment bathing theatoms must be known to high accuracy. To date, imperfect knowledge of this environment has led toclock uncertainties of 3x10-17 or higher. We describe here in detail a radiation enclosure surrounding
the lattice trapped atoms designed to constrain the thermal environment sufficiently well to achieve
1x10-18 clock uncertainty. The shield is designed for operation at either room or cryogenic temperatures.
Finally, we will present early results from comparative measurements between two Yb lattice clocks.
Exploiting an ultra-stable laser for clock interrogation54, both systems have demonstrated measurement
instability at or better than 5x10-16/t1/2. Using this measurement capability, we further characterize lightshifts originating from the optical lattice confinement.

52

J. A. Sherman et al., “High-Accuracy Measurement of Atomic Polarizability in an Optical Lattice Clock”, Phys. Rev. Lett.,
vol. 108, 153002, 2012.
53

K. Beloy et al., “Determination of the 5d6s 3D1 state lifetime and blackbody-radiation clock shifts in Yb”, Phys. Rev. A.,
vol. 86, 051404(R), 2012.
54

Y. Y. Jiang et al., “Making optical atomic clocks more stable with 10-16-level laser stabilization”, Nat. Photonics, vol. 5, p.
158-161, 2011.

IFCS-EFTF6-B3-3

First spectroscopy of the 1S0 – 3P0 transition in Lamb-Dicke
confined magnesium atoms

André Kulosa, Steffen Rühmann, Dominika Fim, Klaus Zipfel, Wolfgang Ertmer, Ernst M. Rasel
Institut für Quantenoptik, Leibniz Universität Hannover, Hannover, Germany
Email: kulosa@iqo.uni-hannover.de
We report on the status of the magnesium optical clock experiment in Hannover. Recently, wedemonstrated the first spectroscopy of the spin-forbidden 1S0 – 3P0 clock transition in µK cold
magnesium atoms that were trapped in an optical lattice at the predicted magic wavelength of 469 nm.
Due to the lack of sub-Doppler cooling techniques, we prepare our atoms using a continuous loading
scheme for an optical dipole trap at 1064 nm55: Atoms with milli-Kelvin temperature are continuouslytransferred to the dipole trap by creating a loss channel for 3P0 atoms. The coldest among them can be
captured by the optical potential for subsequent transfer into the optical lattice.
Applying an external homogeneous magnetic field creates a mixture of the 3P0 and 3P1 states weakly
allowing the 1S0 – 3P0 transition56. Performing such a magnetic field-induced spectroscopy, we havebeen able to de-excite 25% of 3P0 atoms on the 458 nm intercombination transition to the 1S0 groundstate.
The interrogation laser for the ultra-narrow clock transition is a frequency doubled diode laser at 916 nm
stabilized to a vibration insensitive optical cavity. The laser system shows a fractional frequency
instability of y(= 1 s) = 5 x 10-16.
As a next step, we will experimentally investigate the magic wavelength for magnesium.

55
56

M. Riedmann, et al., Phys. Rev. A 86, 043416 (2012)
A. V. Taichenachev, et al., Phys. Rev. Lett. 96, 083001 (2006)

IFCS-EFTF6-B3-4

Mercury optical lattice clock at LNE-SYRTE
R. Tyumenev, Z. Xu, J. J. McFerran and S. Bize.
SYRTE, 61 avenue de l’Observatoire, 75014 Paris, France
Email: sebastien.bize@obspm.fr
An ensemble of atomic clocks is being developed at LNE-SYRTE, comprising Cs and Rb
atomic fountains, two Sr optical lattice clocks, and a Mercury (Hg) optical lattice clock. Hg is avery interesting candidate for making an optical lattice clock, due to several favorable atomic
properties. The 1S0 – 3P0 clock transition in Hg has very low blackbody radiation shift. For
instance blackbody radiation sensitivity in Hg is a factor of 34 less than in Sr. Hg has a highvapor pressure at room temperature, which allows eliminating large temperature gradients inthe experimental setup due to heating systems. Hg atoms can be laser-cooled to rather low
temperature of 30 K with a single stage magneto optical trap (MOT), performed on 1S0 – 3P1
transition, and directly loaded in the optical lattice.
In this poster, we describe our experimental setup and the latest results that we obtained with
it. Atoms are confined in a vertically orientated optical lattice with depth about 20 recoils
energy at 362 nm. Atoms are loaded in optical lattice from a MOT with cooling light at 253.7
nm. Once atoms are trapped in optical lattice, we apply Rabi light pulse at 265.6 nm, deliveredfrom ultra-stable laser source connected to the LNE-SYRTE primary reference signal via
optical frequency combs. High precision spectroscopy experiments allowed us to determine
magic wavelength for Hg with precision up to 10 -3 nm [1]. We demonstrated atomic quality
factors as high as 1014 (11 Hz at 1128 THz), locked an ultra-stable laser to the ultra-narrow 1S0− 3P0 clock transition and demonstrated a fractional frequency instability of 5.4 × 10−15 ∕ for ≤ 400 s [2]. We performed a preliminary study of systematic shifts and a series of absolute
frequency measurements with an uncertainty of 5.7 parts in 1015 [3].
In future, we are planning to improve our cooling light source and have more power in MOT
light beams, increase trap depth in our 1D optical lattice trap, which is a significant challenge
given the magic wavelength in the UV range. This will help us to increase the atom number bymore than one order of magnitude, to improve the signal to noise ratio in the clock transition
spectroscopy, to determine the magic wavelength with increased precision, and to study
systematic frequency shifts down to the 10 -16 level, as a first step before seeking the limits ofthe Hg system which are expected in the low 10 -18 range, at room temperature.

[1] J. J. McFerran et al., PRL 108, 183004 (2012).
[2] J. J. McFerran et al., Optics Letters, 37, 3477 (2012).
[3] J. J. McFerran et al., Oral presentation at the 2012 EFTF.

GNSS and Services
CLUB E
Monday, July 22 2013, 04:30 pm - 06:00 pm
Chair:

Alexander Kuna
Institute of Photonics and Electronics

IFCS-EFTF5-C1-1

Technical Status of Galileo Development
Alexander Mudrak1, Joerg Hahn1, Daniel Blonski 1
1

Galileo Project Office, European Space Agency, Noordwijk, The Netherlands
Email: alexander.mudrak@esa.int

Galileo is Europe’s own global navigation satellite system, providing a highly accurate global
positioning service under civilian control. It is inter-operable with GPS and Glonass, the US and Russian
global satellite navigation systems.
By offering dual frequencies as standard, Galileo will deliver real-time positioning accuracy down to themetre range. Galileo will also disseminate UTC with the accuracy of 30 ns.
Experimental satellites GIOVE-A and GIOVE-B were launched in 2005 and 2008 respectively, serving
to test critical Galileo technologies, while also the securing of the Galileo frequencies within theInternational Telecommunications Union.
On 21 October 2011 the first two of four operational satellites have been successfully launched, two
additional satellites followed on 12 October 2012. Those satellites have been developed together with
the necessary ground infrastructure to validate the Galileo concepts in orbit. This In-Orbit Validation(IOV) phase will be executed during the early summer this year.
The four operational satellites launched so far - the basic minimum for satellite navigation in principle serve to validate the Galileo concept with both segments: space and related ground infrastructure. The
satellites are carrying 2 passive Hydrogen masers and 2 RAFS each.
The IOV satellites form part of the final constellation of satellites and will be followed by additional
satellite launches to reach Initial Operational Capability (IOC) by mid-decade.
At this stage, The Open Service, Search and Rescue and Public Regulated Service will be available withinitial performances. A range of Galileo services will be extended as the system is built up from IOC toreach the Full Operational Capability (FOC) by this decade’s end.
Two Galileo Control Centres (GCCs) have been implemented on European ground to provide for thecontrol of the satellites and to perform the navigation mission management.

IFCS-EFTF5-C1-2

Absolute Timing Calibration of a
GPS/Galileo Combined Receiver
Blair Fonville1, Edward Powers1
Alexander Mudrak2, Joerg Hahn2, Pierluigi De Simone2, Rigas Ioannides2
1

2

U.S. Naval Observatory, Washington, United States
Galileo Project Office, European Space Agency, Noordwijk, The Netherlands
Email: blair.fonville@usno.navy.mil

Future GNSS navigation users will benefit from multiple satellite constellations, with improved satellite
visibility, reduced dilution of precision (DOP), and better multipath mitigation, among others benefits.
In order to utilize multiple navigation systems, receivers must establish within themselves a common
system time reference. Therefore, GPS and Galileo will broadcast GPS-to-Galileo Time Offset (GGTO),
which will enhance the system interoperability.
Through GGTO Subgroup of EU-US WG-A, USNO (representing GPS) and ESA (for Galileo) haveagreed on the methods to compute and coordinate the GGTO values. During the initial stages of thecoordination, and throughout Galileo’s IOV campaign, the different methods will provide validation to
the GGTO computations, ensuring the most accurate results.
One of the techniques to be employed for GGTO determination will utilize a GPS/Galileo combined
receiver. For its proper application, the receiver must be precisely calibrated to account for its internal
time delays among all of the GPS and Galileo channels, which would result in errors in the GGTO
computation. In September of 2012, the USNO team visited the European Space Research andTechnology Centre (ESTEC) in Noordwijk, the Netherlands, to jointly conduct the initial absolute
receiver calibration. Afterwards, the receiver calibration procedure has been consolidated and the final
calibration has been executed in May 2013 for both USNO and ESTEC receivers (commercial off-theshelf models).
This paper described the consolidated procedures and the results of the calibration.

IFCS-EFTF5-C1-3

Research and Compare of Timing Methods for Compass Satellite
Navigation System
H. Sha1, J.W. Zhan1,J.H. Wang, G.Z. Zhang1, G. Ou1
1

Satellite Navigation R&D Center, National Univ. of Defense Technology, Changsha 410073, China
Email: sandhai@163.com

The timing method for the COMPASS system, its full coverage, all-weather, high precision timing, hasbeen widely used in China's electric power, communications, finance and other industries. However,taking into account national security and economic stability, and the COMPASS system timing products
must to be used in the important foundation network relationship to the national economy. Currently, theCOMPASS system timing methods are including the RDSS two-way timing, RDSS one-way timing and
RNSS timing, totaling three methods. There into RDSS two-way timing is active timing mode, has hightiming accuracy, but the limited number of users; the RDSS one-way timing needs to be known locationof the user, has lower timing accuracy; The RNSS timing can be produced the positioning and clock
error data at the same time. This paper first analyzes the system composition and working principle ofthe three timing methods, and explores the various sources of error in timing methods. Then through thebudget of the sources of error, the precision on various timing methods is drawn. Finally, it is detailed
comparison of the three timing methods of performance, features, functions, summed up the direction ofvarious timing application, and its future development prospects.

IFCS-EFTF5-C1-4

Performances of EGNOS Network Time : an update
Delporte Jérôme1, Suard Norbert1, Uhrich Pierre2
12

CNES, French Space Agency, Toulouse, France
LNE-SYRTE, Observatoire de Paris, Paris, France
Email: jerome.delporte@cnes.fr

EGNOS (European Geostationary Navigation Overlay Service) is the European Satellite Based GPS
Augmentation System. It generates its own system time scale ENT (EGNOS Network Time) that is
steered by EGNOS ground control segment to GPS time (GPST). The time offset between ENT and
UTC is broadcast in EGNOS navigation message. To compute that offset, an EGNOS ground station
was set up in Observatoire de Paris and is connected to UTC(OP), the local realization of UTC at LNESYRTE in Observatoire de Paris.
Applying EGNOS corrections on GPS measurements provides a precise time and navigation solution
referenced to ENT. Therefore the assessment of the time difference between ENT and UTC is a key
issue for time users. We previously described the EGNOS ground station in Observatoire de Paris andits connection to UTC(OP)57 and more recently the timing performances of ENT with respect to GPSTand UTC58. We also described a method used to validate the EGNOS Message Type #12 that contains
ENT – UTC(OP). This method is using another dual-frequency GPS time receiver (OPMT) connected to
UTC(OP).
In this paper, we provide an update on:the status of the EGNOS operational service

the performances of ENT with respect to GPST and UTC using more than 5 years of broadcastdata

the performances of the broadcast ENT – UTC(OP) using more than 4 years of real data of
OPMT receiver.

The latter provides interesting indications on the timing stability of the internal delays of both the
EGNOS ground station at OP and the OPMT reception chain used for validation.
Finally, LNE-SYRTE has improved the performances of UTC(OP) since October 201259. The impact
for EGNOS and its time users is discussed.

57

P. Uhrich et al., “The French Time Reference UTC(OP) and the Connection of the EGNOS Network Time”, Proc. of
EFTF 2005, pp. 539-544
58

J. Delporte et al., “EGNOS Network Time and its relationships to UTC and GPS time”, proc. of PTTI 2009.

59

G.D. Rovera et al., “The new UTC(OP) based on LNE-SYRTE atomic fountains”, abstract submitted to this conference.

IFCS-EFTF5-C1-5

Exponential Degrading of NTP Synchronization with Number of
Network Hops
Akihiko Machizawa, Tsukasa Iwama
National Institute of Information and Communications Technology, Tokyo, Japan
Email: machi@nict.go.jp
The Network Time Protocol (NTP) is a standard for time synchronization in IP-based network. There are
hundreds of public NTP servers in the world. Conventional client software select a peer / server using
statistics of packet delay jitters for some manually listed servers, even though it is often said that the nearest
NTP server should be used. What is “nearest”? There are two metrics for network distance 60. One is delay
time and another is hop-count. The hop-count tells the number of routers on the network path. The
communication quality is degraded due to the hop-count, because most of jitters and packet losses occurredat routers. Although it is known that packet delay jitters are proportional to the square root of hop-count61, it
has not yet suggested how much degrading increasing hops affect NTP synchronization. In this article, weshow the client accuracy degrading with the hop-count in a quantitative way. We also propose a nearest NTP
server detection method using Round Trip Hop-counts (RTH). RTH is the total number of hops on the pathfrom a client to a server (forward path) and the backward path.
Fig. 1 plots the standard deviation of one-way delay between our NTP server, ntp.nict.jp, and some client
along the estimated RTH on a semi-log scale. The one-way delay represents the client synchronization,
because it is sum of the clock offset and network delay. The accuracy of time synchronization of clientsdegrades exponentially with the hop-counts. An IPv4 header has a Time-to-Live (TTL) field and an IPv6
header has a Hop Limit (HL) field. Since each router subtracts one count from these fields, the hop-count canbe estimated with the fields. The estimation of RTH is twice of estimated one-way hop-count from clients tothe server.
The forward path and the backward path may bedifferent. We propose TTL/HL reflecting method
at servers to measure the RTH. This method
copies the TTL/HL values of in-coming request
packets at the servers into the field of the outgoing NTP server response packets. The TTL/HL
values are decreased successively throughforward and backward path. The clients canselect the nearest NTP server among listed
servers with this method.
Selecting the nearest server will lead, (1) toimprove client accuracy, (2) to reduce network
traffic, and (3) to reduce power consumption. We
implemented the TTL/HL reflecting function on
the servers associated with ntp.nict.jp (this NTP
server is a multiple IP address host).

Fig. 12: Client accuracy degrading with Round Trip
Hop-count. The standard deviation of one-way
delay from clients to ntp.nict.jp rises exponentiallywith increasing of network distance (RTH).

60

V. Paxson et al. :”Framework for IP performance metrics,” IETF, RFC 2330 (1998)

61

C. Barry et al. :”Synchronization in Packet Networks: Timing Metrics and Monitoring ,” Proc. PTTI 2008

Emerging Sensors
CLUB D
Monday, July 22 2013, 04:30 pm - 06:00 pm
Chair:

Mauricio Pereira da Cunha
University of Maine

IFCS-EFTF4-C2-1

Bernard Legrand1, Marc Faucher1, Lionel Buchaillot1, Estelle Mairiaux1, Benjamin Walter1, Zhuang Xiong11
NAM6, IEMN CNRS, Villeneuve d'Ascq, France

Silicon MEMS resonators: a story from signal processing
devices to Atomic Force Microscopy sensors
Bernard Legrand, Marc Faucher, Lionel Buchaillot,
Estelle Mairiaux, Benjamin Walter, Zhuang Xiong
IEMN – UMR 8520 CNRS, NAM6 group, Villeneuve d’Ascq, France
Email: bernard.legrand@isen.iemn.univ-lille1.fr
Electromechanical micro-resonators (MEMS resonators) are devices that give access in the electrical
domain to the properties of a mechanical resonance thanks to electromechanical transducers. They havebenefited since the 1980’s from surface micromachining processes compatible with silicon integrated
circuit technologies. Many academic and industrial research works have been carried out especially inthe field of signal processing, e.g. filters or time references, but also in the field of sensors. In particular,
MEMS resonators can be used as Atomic Force Microscopy (AFM) probes, taking advantage of higher
resonance frequencies and quality factors thanthose of standard AFM probes based on
cantilevers.
AFM systems have been widely used for 20 years
in academic and industrial work. They give accessto microscopy images at the nanoscale. Many labs
are currently trying to use the oscillating mode of
AFM to probe biological nanosystems and theirdynamics in a liquid environment. However,
AFM performances are limited by the AFM
oscillator itself. It is typically made of a tip
supported by a cantilever beam whose oscillating
properties are drastically degraded once placed ina liquid. Our approach consists in changing the Fig. 13: Atomic Force Microscopy probe based on
MEMS ring resonator. Resonance frequency isoverall AFM oscillator and choosing an in-plane 12 MHz. Capacitive transduction is used to drive
vibration mode in the 10-100 MHz range that and sense the device vibration.
reduces the hydrodynamic damping. This new
generation of high sensitivity AFM force sensor is
expected to be an unprecedented tool for imaging biological and chemical systems at the nanoscale andthe possibility of kinetic spectroscopy in liquids.
The presentation will focus on our recent development of MEMS based AFM probes that make use ofvibrating rings in the range of 10 to 20 MHz with capacitive transducers (Fig. 1). Integration of suchforce sensors in a commercial AFM set-up will be described as well as the imaging capabilities obtainedon DNA origamis samples. Force resolution is currently in the range of a few picoNewtons.

IFCS-EFTF4-C2-2

The Optoelectronic Oscillator as an Acoustic Sensor
Olukayode Okusaga,1 James P. Cahill,1,2 Justin Pritchett,1 Ryan Sorenson,1 Weimin Zhou,1Morris Berman,1 Gary M. Carter,2 Curtis R. Menyuk2
1

2

U.S. Army Research Laboratory, Adelphi, MD
University of Maryland: Baltimore County, Baltimore, MD
Email: olukayode.k.okusaga.civ@mail.mil

In this work, we present a novel fiber-optic acoustic sensor based on a high-Q optoelectronic oscillator(OEO) and a fiber delay-line interferometer. Fig. 1 shows a schematic diagram of our acoustic sensor.
The OEO fiber loop acts as the transducer: converting pressure waves into phase fluctuations on the
OEO’s RF signal. Fiber-based sensors typically have greater dynamic range than other highperformance sensors. In addition, the low loss-per-unit-length of optical fiber allows for the use of fiberspools that over 100 m long: increasing acoustic sensitivity and range. However, optical scattering infibers tends to distort the measured signal spectrum.62 By detecting phase fluctuations – not on the laser
carrier – but on the OEO’s RF signal, we have constructed a long-fiber-loop acoustic sensor with both
high sensitivity and spectral resolution.
At offset frequencies that are relevant for acoustic sensing – <1 Hz to 100 kHz – the OEO’s phase noise
is over 60 dB lower than that of a typical laser

Fig. 14: A schematic diagram of our OEO-based Fig. 2: Plots of the measured acoustic signal fromacoustic sensor.
the OEO-based and a conventional fiber sensor.

used in sensing applications. In addition, by suppressing optical scattering63 in the OEO’s fiber spool,
we suppress the effects of fiber-induced noise on the detected acoustic spectrum. The result, as shownin Fig. 2, is an acoustic sensor with both high sensitivity and frequency resolution. Our OEO-based
sensor can detect a 10 dBa signal with sub-Hertz resolution. In Fig. 2, we have included data measured
using a conventional fiber-optic interferometer to measure the same 1 kHz acoustic source forcomparison.

62

O. Okusaga, J. Cahill, W. Zhou, A. Docherty, G. M. Carter, C. R. Menyuk, "Optical scattering induced noise in RFphotonic systems," Frequency Control Symposium (FCS), 2011 IEEE International, pp. 1–6, 2011.
63

O. Okusaga, W. Zhou, J. Cahill, A. Docherty, C. R. Menyuk, "Fiber-induced degradation in RF-over-fiber links,"
Frequency Control Symposium (FCS), 2012 IEEE International, pp.1-5, 21-24 May 2012.

IFCS-EFTF4-C2-3

TOWARDS A SAW BASED PHONONIC CRYSTAL SENSOR
PLATFORM
R. Lucklum1, M. Zubtsov1, M.-P. Schmidt2, A. Oseev1, S. Hirsch2, Falk Hagemann3
1Institute of Micro and Sensor Systems, Otto von Guericke University Magdeburg, Germany
2
Teprosa GmbH, Magdeburg, Germany
3
SAW Components Dresden GmbH, Germany
Email: ralf.lucklum@ovgu.de

A sensor platform based on phononic crystals specifically attractive for biosensing will be introduced.
The unique feature of this sensor concept is the determination of volumetric properties of analytes atvolume as low as 1 nl and less. The sensor platform has the capability paving the way to study
biomaterials directly in their physiological environment without any label.
Phononic Crystals (PnC’s) belong to the group of metamaterials. These artificial materials areengineered to have properties that have not been found in nature. The typical structure consists ofperiodically arranged scattering centers with properties different to a homogeneous matrix. Sensors aredesigned in a way that the PnC offers specific mini transmission bands realized with certain defectstructures. The material of interest constitutes one component of the phononic crystal, e.g., a liquid in a
fluidic channel as part of the PnC64. Meeting the typical dimensions of microfluidic systems requires
frequencies in the range of several MHz to several 100 MHz. Higher frequencies contribute to enhanced
sensitivity. The key difference to acoustic or micromechanical resonators is that the resonance frequencyof the PnC cavity is strongly governed by the group velocity of sound of the confined liquid or relatedparameters, not by properties of a sensitive film immobilized on the surface of the resonator (although
this version is another way of exploiting the sensor platform).
The challenge to access higher frequencies is threefold: Devices providing good electromechanicalcoupling and low insertion loss at MHz frequencies, design of the PnC with appropriate band gaps,
technology to realize the structure. Most appropriate for acoustic waves in the mid-MHz range are
piezoelectric surface acoustic wave (SAW) devices. It has been shown previously that phononic crystal
designs exist featuring a full band gap for SAW65. However, significant extension of the models is
required to incorporate a liquid into the structure.
Numerical simulations (Comsol Multiphysics) deal withfinding the desired design to achieve a band gap
overlapping with the transmission region of the SAW
device. Unfortunately, etching technology is far lessdeveloped for piezoelectric materials compared to Si.
Wewill present our theoretical and experimental results
achieved with quartz-based wafers. Figure 1 shows
100 µmexemplarily an array of etched holes as required for
different SAW frequencies.
Fig. 1: SEM picture of a set of holearrays etched into a quartz crystal.

64

R. Lucklum, M. Ke, M. Zubtsov, Sensors Actuators B 171-172, 271-277 (2012).

65

V. Laude, M. Wilm, S. Benchabane, A. Khelif, Phys. Rev. E 71, 036607 (2005).

IFCS-EFTF4-C2-4

Absolute phase and amplitude mapping of surface acoustic wave
fieldsDamien Teyssieux, Thomas Baron, Jean-Michel Friedt and Pascal Vairac
FEMTO-ST, UMR CNRS 6174, 32 Avenue de l’Observatoire, F-25044 Besançon, France
Email: damien.teyssieux@femto-st.fr
Energy confinement in acoustic transducers is a significant parameter since it is closely related to thequality factor of the device. Thus, mapping acoustic energy at the surface of bulk and surface acoustic
devices is of significant interest in validating design parameters and identifying sources of energy
leakage. In this context, a scanning heterodyne interferometer is presented for acoustic wave acoustic
energy mapping with the measurement of the absolute phase and out-of-plane vibration amplitude in the[5-1200] MHz range. The flexible experimental setup allows for a vibration detection limit of 10 pm andthe frequency range can be increased up to 4.5 GHz
by only improving the photo-detector bandwidth.
We consider the acoustic energy mapping and acomplementary analysis to the classical electrical Sparameters characterization since the latter isinsufficient for a good acoustic phenomena
comprehension. Consequently, several opticalsetups have been developed in order to measure thesurface acoustic vibrationviiviiiix
The presented interferometer is based on a doublepass structure which presents several advantages
compared with the classical structure: simplicity(fewer components) and ease of alignment. A
dedicated high frequency demodulator is used inorder to detect the absolute phase of the vibration,with obsolute amplitude obtained without
calibration due to the heterodyne structure. The
scanning speed depends on the amplitude of thevibration and can be around >50000 points per hour(for a vibration of 100 pm). Phase unwrapping
demonstrates consistent slope with the expected
acoustic velocity in the mirrors of a resonator andthe standing wave is observed in the acoustic cavity.

Fig. 15: Vibration amplitude (pm)Fig. 16 : Vibration phase (°)
Acoustic energy distribution on a single-port
quartz SAW operating @ 392 MHz.

IFCS-EFTF4-C2-5

Mapping Thermomechanical Vibrations and Mode Shapes
in High Frequency SiC-on-Insulator Nanoscale Resonators
Jaesung Lee1*, Zenghui Wang1, Mehran Mehregany1, Philip X.-L. Feng1*
1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
Email: jaesung.lee@case.edu, philip.feng@case.edu

We report on experimental demonstration of multi-mode radio-frequency nanomechanical disk resonators ina novel 500nm SiC-on-insulator (SiCOI) technology, and on measurements of directly mapping the modeshapes of the multiple resonances with high spatial resolution. By employing and engineering ultrasensitive
optical interferometric techniques, we measure the lowest possible levels of vibrations, i.e., the undriven
thermomechanical resonances arising from the intrinsic Brownian motions, in these SiCOI disk resonators.
Spatially mapping the resonant mode shapes of multi-mode nanomechanical resonators can greatly facilitate
understanding and harnessing these multiple modes for sensing and frequency control applications.
Our resonant devices (500nm-thick poly-SiC disks anchored on SiO2 center pedestals) feature a uniform
optical cavity (depth=500nm) with the underneath Si substrate. We use an optical interferometer with
fm/Hz1/2-level displacement sensitivity66,67, to transduce the thermomechanical motion of the device into
electrical signals. The ~1μm laser spot enables spatially mapping the different resonance modes.

S1/2(V/Hz1/2)
V

S1/2(V/Hz1/2)
V

S1/2(V/Hz1/2)
V

Figure 1 shows measured noise
0.8(a)spectraldensityof
five
0.6
mechanical resonance modes.
The peak amplitude of the mode
0.4
strongly depends on the laser
16.4
16.5
10.10 10.15
10.35 10.40
12.15 12.20
0.2
spot position (see insets). In the
0.8
center of the disk (position (a)),(b)
no measurable motion signal is0.6
observed. In the positions (b)0.4
and (c), we detect 5 and 4
resonance modes, respectively.
0.2
Measured resonance frequencies
0.8(c)and spatial maps of the mode
0.6
shapes (center row insets) agree
very well with COMSOL
0.4
simulation results (bottom row
0.2
insets).
We also observe
10
15
20interesting effects such as theFrequency (MHz)off-center position of the Fig. 1: Measured thermomechanical resonance spectra. Right insets:pedestal lifting the frequency optical images showing the exact actual positions of the laser spot. Top
degeneracy between the first two insets: plots of resonances with fit (same y axis and scale as in main plots).
modes
and
breaking
the Middle insets: spatial intensity map for each mode. Bottom insets:
azimuthal symmetry in the mode COMSOL simulation of the mode shapes. Top right: SEM image (scale
shape of the third resonance bar: 10µm).
mode, as well as electronically tuning the resonances, which we will report in detail in the full paper.

66
67

W. K. Hiebert, D. Vick, V. Sauer, M. R. Freeman, J. Micromech. Microeng. 20, 115038 (2010).
J. Lee, P. X.-L. Feng, Proc. IEEE Inter. Freq. Contr. Symp. (IFCS2012), DOI: 10.1109/FCS.2012.6243742.

Optical Combs I
CLUB H
Monday, July 22 2013, 04:30 pm - 06:00 pm
Chair:

Jason Jones
University of Arizona

IFCS-EFTF6-C3-1

Tobias Kippenberg1
1
EPFL, Switzerland

Soliton mode-locking in optical microresonators
T. Herr1, V. Brasch1, J.D. Jost1, C.Y. Wang1, N.M. Kondratiev2, M.L. Gorodetsky2, T.J. Kippenberg1,3
1

École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
2
Faculty of Physics, Moscow State University, Moscow 119991, Russia
3
Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

Abstract: We demonstrate soliton mode-locking in continuously pumped, non-linear optical MgF2
microresonators, resulting in low noise frequency comb spectra and ultra-short pulses of 200 fs duration
with a repetition rate of 35.2 GHz.
OCIS codes: (140.3945) Microcavities; (190.4380) Nonlinear optics, four-wave mixing; (060.5530) Pulse propagation and temporalsolitons; (140.4050) mode-locked lasers; (140.7090) Ultrafast lasers; (190.7110) Ultrafast nonlinear optics

The discovery of passive mode-locking via saturable absorbers has led to optical femto-second pulses
with applications ranging from eye-surgery to the analysis of chemical reactions on ultra-shorttimescales. In the frequency domain a train of such optical pulses corresponds to a frequency comb
(equidistant optical laser lines spaced by the pulse repetition rate), which finds use in precision
spectroscopy and optical frequency metrology. Not relying on mode-locking, and without the formationof pulses, frequency combs can also be generated in continuously driven, high quality-factor, Kerrnonlinear optical microresonators via cascaded four-wave mixing. Applying a pulse-shaping modelocking mechanism to such microresonator based frequency combs could enable compact and robust
femto-second pulse generators. However, saturable absorbers are challenging to apply to
microresonators as they affect the high quality factor essential to nonlinear frequency conversion.
Here, we demonstrate passive mode-locking of a microresonators comb via soliton formation without
saturable absorber. Indeed solitons are stable and attractive states of the system and a saturable absorber,as required for stability in soliton mode-locked lasers, is not necessary. The formation of solitons isenabled by the balance between anomalous resonator dispersion and Kerr-nonlinearity. The employed
crystalline MgF2 resonator, has a coupled resonance width of 450 kHz and a free-spectral range of 35.2
GHz. Frequency combs can be generated when coupling a continuous wave pump laser (10-100 mW,
1553 nm) to the resonator via a tapered fiber. The transitions to and between different soliton modelocked states manifest themselves as discrete steps in the transmission signal when scanning the pumplaser over a resonance. These steps deviate markedly from the expected triangular, non-linear resonanceshape (cf. Fig. 1b). Each step corresponds to a change of state, namely the number of solitons
propagating inside the resonator. When tuning the pump laser into a soliton mode-locked state, we
observe the generation of pulses with 200 fs duration (detected by frequency resolved optical gating,
FROG). The generated optical spectra are low noise as evidenced by the narrow repetition rate beatnote
at a frequency of 35.2 GHz. In the single soliton case the frequency comb spectrum shows very little
line-to-line power variation, as required for broadband telecom and spectroscopy applications.
Numerical simulations based on coupled, non-linear mode equations reproduce the step features and theformation of multiple and single cavity solitons. These simulations are also in excellent agreement withan analytical model of solitons on a weak continuous wave background. In addition, we verify that thesolitons in the microresonator can be analytically described by the solutions of the driven, damped nonlinear Schroedinger equation.
The presented results open the route towards compact microresonator based femto-second sources,
where the parametric gain in principle gives access to pulse center wavelength that are difficult to accessusing conventional mode-locked lasers, such as the mid-infrared. Our observations apply equally toother microresonator comb platforms. In this context, we note that independent research has very

recently reported on femto-second pulse generation and mode-locking in Si3N4 microresonators. The
smooth optical soliton spectra are essential for frequency domain applications such as channel
generators in advanced telecommunication or in fundamental studies such as astrophysical spectrometer
calibration. Moreover, femto-second pulses in conjunction with external broadening provide a viable
route to a microresonator based RF-to-optical links.

IFCS-EFTF6-C3-2

Low-noise 1-micron optical frequency comb based on diodepumped solid-state laser technology
S. Kundermann, Erwin Portuondo-Campa, Jonathan Bennès, Steve Lecomte
Time & Frequency, Centre Suisse d’Electronique et de Microtechnique, Neuchâtel, Switzerland
Email: steve.lecomte@csem.ch
Optical frequency combs (OFCs) have revolutionized the way optical frequency metrology can be done
since more than 10 years and are a key component in optical atomic clocks. Initially demonstrated with
Ti:Sapphire lasers, optical frequency combs have been generated with several other laser technologies.
Fiber laser technology at wavelengths of 1 micron and 1.55 microns has been the object of many efforts
for improving their performances and in particular the noise properties. OFCs based on passively modelocked diode-pumped solid-state lasers (DPSSLs) have been less studied while offering excellent
prospects for low-noise high-performance operation due to the low-loss low-gain laser configuration. A
1.55-microns DPSSL has been self-referenced and characterized in Ref. 68 while in Ref. 69 a selfreferenced 1-micron Yb:KYW has demonstrated state-of-the-art low phase-noise microwave generation.
Here we present a passively mode-locked diode-pumped Yb:glass laser that has been self-referenced.
The laser is mode-locked via a saturable absorber mirror and delivers 111 fs transform limited soliton
pulses with an average output power of 205 mW at a repetition rate of 100 MHz. After propagation in ahighly nonlinear optical fiber, the laser pulses generate
an octave spanning supercontinuum amounting
110 mW of average power which is then sent into an f2f Michelson interferometer for carrier-envelope offset
frequency (f0) detection. No external optical amplifieris needed. A signal-to-noise ratio of up to 40 dB for f0(at an instrument resolution bandwidth of 91 kHz) has
been detected. Using standard locking electronics andfeedback to the pump diode injection current, f0 was
phase locked to an H-maser referenced microwave
synthesizer. The in-loop integrated phase noise Fig. 17: Phase-noise power spectrum density
amounts 736 mrad when integrated from 1 Hz to of the divided by 16 274-MHz carrierenvelope offset frequency
1 MHz for a measured f0 frequency of 274 MHz (seeFig. 1). The achieved integrated phase noise is comparable to the best fiber lasers. The f0 phase-locking
is very robust and lasts for days. The relative intensity noise (RIN) of the laser has been measured. For afree-running laser, at offset frequencies above the laser pump modulation bandwidth (100 kHz), shotnoise limited RIN is achieved with a level of -154 dBc/Hz.
In conclusion we have demonstrated a robust and low-noise self-referenced passively mode-locked
diode-pumped Yb:glass solid-state laser. The authors would like to thank the Canton de Neuchâtel for
financial support and Scott Diddams and Stephanie Meyer for helpful discussions.

68

S. Schilt et al., “Fully stabilized optical frequency comb with sub-radian CEO phase noise from a SESAM-modelocked
1.5-μm solid-state laser” Opt. Expr. Vol. 24, p. 2471-24181, 2011
69

S. Meyer, T. M. Fortier, S. Lecomte, S. A. Diddams, “A frequency-stabilized Yb :KYW femtosecond laser frequency
comb and its application to low-phase noise microwave generation”, submitted to Appl. Phys. B

IFCS-EFTF6-C3-3

Terahertz activities based on an optical frequency comb
Motohiro Kumagai, Shigeo Nagano, Hiroyuki Ito, Masatoshi Kajita, Yuko Hanado
Space-time Standards Laboratory
National Institute of Information and Communications Technology (NICT), Tokyo, JAPAN
Email: mkumagai@nict.go.jp

Research at Terahertz (THz) frequencies is very active in applications such as material analysis, wirelesscommunication, remote sensing, and biological imaging. However, no accurate frequency standard
exists in THz region. This has led NICT start research to establish a new frequency standard in the THz
region.
Firstly we address the absolute frequency measurement of a THz frequency continuous wave (CW.) Our
measurement system is based on a femto-second (fs) pulse fiber laser comb and a photoconductive
antenna (PCA). Pulsed light from the fs fiber laser is focused onto the antenna gap of the PCA. In theantenna, a time-varying photocarrier is created and its Fourier expansion forms a comb structure. The
comb structure mode extends to THz region, resulting in the generation of frequency grids in the THz
region, which we call “THz comb”. By mixing the THz comb and the CW-THz, an absolute frequency
measurement is possible. In a measurement of a 300GHz wave, we have confirmed that themeasurement system has a fractional instability at the 10-16 level at averaging time of over 1000 seconds.
The present resolution is limited by the electronic noise of the current-to-voltage conversion amplifier
used at the output of the PCA. The photocarrier THz comb can be used for not only microwave-to-THz
conversion but also THz-to-microwave conversion. We have demonstrated a generation of low-phasenoise microwave signal synthesized from a 0.3 THz radiation. The phase information of the 0.3 THz
signal was copied to the 1GHz signal without degradation. This technique potentially transfers the phase
information of THz radiation into accessible microwave region.
THz CW generation by photomixing of two optical lasers whose frequencies have a THz-levelseparation is capable of providing an accurate frequency reference. One candidate for such a techniqueis the use of two optical modes of a mode-locked laser whose repetition frequency is well-stabilized.
However, it is difficult to extract only two modes from the mode-locked laser with a conventional
optical bandpass filter (a bandwidth of about 10 GHz) because the repetition frequency of the laser isnormally less than 1GHz. By applying ultra-narrow optical filtering based on stimulated Brillouinscattering to the fs fiber comb we have successfully extracted only two optical modes and generated ahighly accurate and high contrast 100GHz wave using an uni-travelling carrier photo detector.

IFCS-EFTF6-C3-4

Robust, frequency-stable and accurate mid-IR laser spectrometerbased on frequency comb metrology of quantum cascade lasers
up-converted in orientation-patterned GaAs
S. Schiller1, M. Hansen1, I. Ernsting1, S. Vasilyev1, A. Nevsky1
A. Grisard2, E. Lallier2, B. Gerard2
1

2

Heinrich-Heine-Universität Düsseldorf, Germany
Thales Research and Technology / III-V Lab, Campus Polytech., 91767 Palaiseau, France
Email: step.schiller@uni-duesseldorf.de

The mid-infrared spectral range (12 µm >  > 4.5 µm) is of interest in both applied and fundamental
spectroscopy. Approaches pursued for enabling mid-IR spectroscopy are based on generating the desiredradiation by down-conversion, either of frequency combs or of cw near-IR sources. Such downconverted
sources, however, typically have low spectral power density. Upconversion of the mid-IR radiation to thenear-IR range provides a way to take advantage of the frequency measurement capabilities of the standard
Erbium-fiber frequency comb. In this work we present a simple and robust solution applicable to the whole
mid-IR spectral range, based on the use of quantum cascade lasers (QCL) as the source of spectroscopic
radiation.
Orientation-patterned gallium arsenide is used as the nonlinear material to generate the sum-frequency
wave of a QCL with a standard high-power cw Erbium fiber laser. The sum-frequency wave is further
amplified by a semiconductor amplifier. Continuous measurements of this wave’s and the fiber laser’s
frequency by a standard Erbium fiber frequency comb provide sinals allowing frequency control of the MIR
laser. The proof of principle is performed with a quantum cascade laser at 5.4 µm, which is upconverted to
1.2 µm. Both the QCL and the cw fiber laser are stabilized to the frequency comb using feedback control. At
the same time, the absolute QCL frequency is determined relative to an atomic frequency reference. We
achieved a frequency instability at the sub-10 kHz-level and also long-term stability and controlled frequency
tuning.
With its current performance and its ease of use, this type of spectrometer could be used e.g. forphotoacoustic spectroscopy, multipass-cell spectroscopy, integrated cavity output spectroscopy, or Lamb-dip
spectroscopy.

Fig. 1 Left: Long-term frequency stability of the QCL. Right: Spectrometer frequency scan over a range of 2.5 GHz,
performed by scanning the repetition rate of the frequency comb. An absorption line of N2O was recorded simultaneously.
Bottom: QCL frequency linear fit residuals.

IFCS-EFTF6-C3-5

Long distance phase-coherent link between near- and midinfrared frequencies
B. Argence1, B. Chanteau1, O. Lopez1, D. Nicolodi2, G. Santarelli2,3, C. Chardonnet1, C. Daussy1, B.
Darquié1, Y. Le Coq2, A. Amy-Klein1
1

Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, Villetaneuse,France2
LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France
3
Laboratoire Photonique, Numérique et Nanosciences, Université de Bordeaux 1, Institut d’Optique and
CNRS, Talence, France
Email: berengere.argence@univ-paris13.fr
Ultra-high-resolution spectroscopy enables to test fundamental physics with molecules as for instancethe non conservation of parity70 or the stability of the electron-to-proton mass ratio71. However many ofthese tests rely on the availability of ultrastable and accurate laser sources emitting in the mid-infrared(IR) where molecules exhibit rovibrational transitions. It is thus very challenging to develop afrequency stabilization scheme in the mid-IR with performance similar to the visible and near-infrared
domain.
For that purpose, we have built a frequency chain which enables to transfer coherently the stability andaccuracy of an ultrastable laser emitting at 1.54 µm to the mid-IR spectral region (Fig. 1). Thisultrastable signal is generated at LNE-SYRTE where its frequency is measured against a set of primary
standards using an optical frequency comb. It is transferred from LNE-SYRTE to LPL through an
optical link72. A second optical frequency comb is phase-locked to this signal and, using sum-frequency
generation in a nonlinear crystal73, the midSYRTE
LPL
43 km
IR
frequency
isHigh-resolution
Primary
Ultrastable
Mid-IR
molecular
comparedtoahigh1,54
µm
laser
laser
clocksspectroscopy
Stability andharmonic of the comb
200 THzaccuracy transfer 30 THz
repetition rate.
With this set-up, we
stabilized a CO2 laser
and obtained a relative frequency stability at the state-of-the art74. We are now progressing towards theextension of this stabilization scheme to Quantum Cascade Lasers.
Fig. 18: Principle of the mid-IR frequency stabilization

70

B. Darquié et al, “Progress toward a first observation of parity violation in chiral molecules by high-resolution laser
spectroscopy”, Chirality, vol. 22, pp. 870-884, 2010.
71
A. Shelkovnikov et al, “Stability of the Proton-to-Electron mass ratio”, Phys. Rev. Lett., vol. 100, p. 150801-150803, 2008.
72
O. Lopez et al., "Cascaded multiplexed optical link on a telecommunication network for frequency dissemination," Opt.
Expr., vol. 18, p. 16849-16857, 2010.
73
A. Amy-Klein et al, “Absolute frequency measurement of an SF6 two-photon line using a femtosecond optical comb andsum-frequency generation”, Opt. Lett., vol. 30, p. 3320-3322, 2005.
74
V. Bernard et al, "CO2 laser stabilization to 0.1-Hz level using external electrooptic modulation", IEEE J. of Quant. Electr.,
vol. 33, pp. 1282-1287, 1997.

IFCS-EFTF Group 1 poster session 1
Forum Hall
Monday & Tuesday, July 22-23, 2013, 01:00 pm - 02:00 pm and 3:30 pm - 4:30 pm
Chair:

Derek Puccio
Quartzdyne

IFCS-EFTF1-PAB1-1

Improving frequency Control of Temperature Compensated Surface Acoustic Wave
Devices
Sergey Mishin

Michael Gutkin

Advanced Modular Systems, Inc
Goleta, CA/USA
smishin@amssb.com

Advanced Modular Systems, Inc
Goleta, CA/USA
mgutkin@amssb.com

A. Bizyukov

Vladimir Sleptsov

School of Physics and Technologies
Karazin Kharkiv National University. Kharkiv,
UkraineMoscow State Aviation Technological University
Moscow, Russia

Abstract— In this paper, we demonstrated improvement of
frequency uniformity for Temperature Compensated Surface
Acoustic Wave (SAW) devices. SiO2 has been used to obtain low
Temperature Coefficient (TempCo) in SAW devices for more than
three decades [1]. One of the big issues is that SAW devices have tobe processed at temperatures below 300C. When low temperature
SiO2 is exposed to the ambient environment, it interacts with
ambient humidity [2], [3], [5], [6]. Such interactions can change
frequency of the SAW devices and can make frequency trimmingwith a focused Ion Beam [7], [8] extremely challenging. UV andsteam treatment of SiO2 improved trimming rate stability on the firsttrimming [4] and [9], but was not sufficient to provide tightfrequency control required for SAW devices after the second
trimming. Using silicon nitride (Si3N4) capping layer on top of SiO2
showed some improvement in frequency control after trimming
process. Most improvement was obtained using aluminum nitride(AlN) capping layer on top of SiO2 followed by two trimming steps.

.

Figure 1. Average Frequency as a function of time
exposure to atmosphere for different methods of SiO2
treatments and capping processes

Figure 2. Cross wafer Frequency variation as a function oftime exposure to atmosphere for different methods of SiO2
treatments and capping processes
REFERENCES[1]

Willingham, C.B., et.al., “Temperature Compensated Surface Wave Devices”, UnitedStates Patent #3965444I. S. Jacobs and C. P. Bean, “Fine particles, thin films andexchange anisotropy,” in Magnetism, vol. III, G. T. Rado and H. Suhl, Eds. New
York: Academic, 1963, pp. 271–350.

[2]

H.A.Naseem, et.al., “Stress and bonding characterization of PECVD silicon dioxide
films”,Electrochemical Society, Vol.97-10, pp.217-226,4-9 May,1997[3]

Leplan H., “Ressidual stresses in evaporated silicon dioxide thin films: Correlation
with deposition parameters and aging behavior”, Journal of Applied Physics, pp.962968, 1995

[4]

M.S. Haque, et.al., “Post-deposition processing of low temperature PECVD silicon
dioxide films for enhanced stress stability”, Thin Solid Films, Volumes 308-309,
1997, pp. 68-73[5]

Leplan H., “Kinetics of residual stress evolution in evaporated silicon dioxide films
exposed to room air”, Journal of Applied Physics, pp.6926-6931, 1996

[6]

Parada E. G., “Aging of photochemical vapor deposited silicon oxide thin films”,
Journal of Vacuum Science &Technology, Volume 14, pp.436-440[7]Quiang Zou, et.al., “High Coupling Coefficient Temperature Compensated FBAR
Rsonator for Oscillator Apllication with wide Pulling Range”, 2010 IEEE
International Frequency Control Symposium, pp. 646-650[8]S. Mishin, “Improving Manufacturability of Bulk Acoustic Wave and Surface
Acoustic Wave Devices”, SPAWDA 2011, IEEE

[9]S. Mishin, et.al., “Production Issues in Using Silicon Dioxide Films for Temperature
Compensated Bulk and Surface Acoustic Wave Devices”, 2012 IEEE International
Frequency Control Symposium

IFCS-EFTF1-PAB1-2

Investigation of the electrode coating influence on the frequency
temperature characteristics of the resonators operating at the rotated Ycut Ca3TaGa3Si2O14 single crystals
Andrey Medvedev, Aleksey Zabelin, Svetlana Bazalevskaya, Oleg Buzanov, Sergey SakharovОАО «Fomos - Materials», Moscow, Russia
medvedev@newpiezo.com[INTRODUCTION] More stringent requirements for temperature stability of piezoelectric devices haveencouraged the development of new materials for use in resonators and filters operating on bulk acoustic
waves. Ca3TaGa3Si2O14 (CTGS) single crystal is of special interest. CTGS has small frequency deviation in
the temperature range (temperature frequency coefficient of the second order (TFC(2)) is about −0.026
ppm/(°C-2) [1], −0.039 ppm/(°C-2) [2]). In this work, the influence of electrode materials and sizes onfrequency temperature characteristics of CTGS resonators operating at TS-mode was investigated.
[EXPERIMENTAL] Piezoelectric resonators were made from CTGS crystals grown by CZ method. The
plates of six cuts (YZw)–25°, (YZw)–22°20', (YZw)–21°20', (YZw)–21°, (YZw)–20°30', (YZw)–20° were
produced. The fundamental frequency of TS-mode was about 10.8 kHz. Electrodes of different sizes andfrom diverse metals (Al, Ag and Au) were deposited. The thickness of the electrodes was 200 um. The
measurements of the temperature frequency characteristics were performed in the S&A W2200B
Temperature Test System. The attenuation characteristics of the CTGS resonators were measured using
Agilent Е5061А specter analyzer.
[RESULTS AND DISCUSSION]
The frequency temperature characteristic of the CTGS resonators
operating at rotated Y- cuts is represented by a parabola. The dependences of turnover temperature asfunctions of angle cuts for different diameters of Ag electrodes are given in fig.1. TFC (2) for −21°20' angle
cut is −0.022 ppm/ (°C-2). Also, for this angle, the ratio of the electrode diameter to the plate thickness(Bechmann’s number) has been obtained (fig.2) below which there is only one discrete eigenmode. The
investigation results of the frequency temperature and amplitude frequency characteristics of CTGS
resonators with Al and Au electrodes will be shown at the conference.

Fig. 1: Turnover temperature vs. rotation angle
for Ag electrodes.

_________________________[1] Shen Jen et al.:2002 IEEE Int. Freq. Con. Symp., p.307-310[2] Fapeng Yu et al.:J. Appl. Phys. 109,114103 (2011)

Fig. 2: Bechmann’s number vs. thickness of
Ag electrodes.

IFCS-EFTF1-PAB1-3

IR-reflectance assessment of the tilt angle of AlN-wurtzite films
for shear mode resonators
Jimena Olivares1, Mario de Miguel-Ramos1, Enrique Iborra1, Marta Clement1, Milena Moreira2, Ilia
Katardjiev2
1
GMME-CEMDATIC-ETSIT, Universidad Politécnica de Madrid, Madrid, Spain
2
Department of Solid State Electronics, Uppsala University, Uppsala, Sweden
Email: eiborra@etsit.upm.es
Shear mode resonators are becoming increasingly interesting as biochemical sensors due to theircapacity to operate in liquid media. Previous studies show that, unlike longitudinal mode resonators, thequality factor and the electromechanical coupling factor of shear resonators do not diminish as muchwhen operating in liquid media. Transverse electric fields can excite shear modes in AlN films exhibitinga nonzero c-axis mean tilt with respect to the normal through the component of the field normal to the caxis and the piezoelectric coefficient d15. Assessment of the c-axis tilt of AlN microcrystals is usually
performed by x-ray diffraction, by scanning the ψ axis when θ is fixed at the value of the (00·2) direction.
However, such a measurement is time-consuming and difficult to implement in-line. Infraredcharacterization is a fast and reliable alternative to XRD. In this communication we assess the angle
between the c-axis of AlN microcrystals and the substrate surface by evaluating the wavenumber of thelongitudinal optical (LO) vibrational mode absorption band obtained from the IR reflectance spectrum of
the film surface.
AlsiliconXRD
ψ axisIR spectra and AFM images
3000

Tilt=0º2500

AbsorbanceAlN films with tilted grains were
deposited by off-axis sputtering of antarget in Ar/N2 mixtures on oxidized
wafers covered with a metallic layer.
θ/2θ patterns and the dispersion in theof the (00·2) AlN reflection were
measured along the wafer in several
positions. Infrared reflectance spectra
provided the local thickness of the AlN
and the structure of the A1-E1
combined absorption LO mode, which
related to the tilt of the c-axis of AlN
figure). Bow measurements done byprofilometry gave the local in-plane
Atomic force microscopy was used tothe surface topography of the films.

2000

1500

film

Tilt=29º

is
(see

1000

500

stress.
assess

0
860

880

900

920

940

Band position (cm-1)

960

The tilt angle of the c-axis oriented
AlN
microcrystals measured by XRD varied from 0° at the center of a 100 mm-wafer to 34° at its edge. Thiswas correlated with the position of the band of A1-E1 mixed LO mode, which was shifted towards
greater wavelengths as the tilt angle increased. The influence of stress on the position of the IR band was
negligible compared to the shift associated to the increasing tilt of the grains. IR reflectancemeasurements offer a straightforward non-destructive diagnostic method for the assessment of tilted
grains in AlN films.

IFCS-EFTF1-PAB1-4

Measurement of independent piezoelectric constants of alanthanumgallium silicate family crystals by x-ray diffraction
methodBuzanov Oleg1, Irzhak Dmitrii2, Roshchupkin Dmitry2
1

2

OAO Fomos materials, Moscow, Russsia
Institute of Microelectronics Technology and High-Purity Materials RAS,
Chernogolovka, Russia
Email: irzhak@iptm.ru

This work presents results of measurements of piezoelectric tensor components for a lanthanum
gallosilicate family crystals with x-ray diffraction technique using. For crystal of this family (point
group 32, space group P321) the piezomodulus tensor has only two independent components d11 and d14.
The method used to measure piezoelectric constants of the studied material is based on the phenomenonof reverse piezoelectric effect. The effect consists in that a piezoelectric crystal undergoes deformation
when external electric field is applied to it. In
certain crystallographic directions, the appliedexternal
electric
field
would
cause
compression or tension of the crystal lattice(diagonal components of the deformation
tensor). It should be noted that diagonalcomponents of deformation tensor are nothing
short of the interplanar spacing changing incorresponding direction. Changes of theinterplanar spacing in the crystal can bemeasured by x-ray diffractometry through Fig. 19: Rocking curves measured on (440)following the changes of the Bragg peak reflection of calcium-tantalum gallosilicate crystal
position. Experimental rocking curves under applied voltage: “+” +1900 V, “-” -1900 V,
demonstrated this phenomenon are shown on “0” 0 V.
Fig. 1.
It should be noted that single-crystal X-cut plate is sufficient for the measurement of both piezoelectric
constants d11 and d14. In this case reflection and transmission geometries of Bragg diffraction should be
used.

IFCS-EFTF1-PAB1-5

Method of controlling coupling coefficient in sputtered Aluminum
Scandium Nitride for high volume production.
Sergey Mishin1, Michael Gutkin1, Alexander Bizyukov2 , Vladimir Sleptsov3
1

Advanced Modular Systems, Inc, Goleta, CA/USA, smishin@amssb.com
Karazin Kharkiv National University, Kharkiv, Ukraine
3
Moscow State Aviation Technological University Moscow, Russia
Email: smishin@amssb.com; mgutkin@amssb.com
2

Abstract— In this paper, we studied the effect of stress of Aluminum Nitride film containing various
concentrations of Scandium (Sc). Coupling coefficient (kt2) was measured across wafer and wafer towafer as a function of stress and Sc content of the film. Previous studies demonstrate a considerable
increase in kt2 as a function of Sc content of the film [1], [2], [4], [5]. Unfortunately, when deposited on
200mm wafers we observed that kt2 varies significantly more than that of standard Aluminum Nitride(AlN). Both stress and concentration of Sc must be controlled across a wafer to achieve uniform kt2
acceptable for production of Bulk Acoustic Resonator (BAW) devices [3], [6], [7]. We were able tocontrol kt2 across a wafer and wafer-to-wafer by adjusting magnetic fields in our magnetron as well as
adjusting concentration of Sc in our two sputtering targets.

Figure 1. Variation of kt2 as a functionof stress for AlN and AlScN films

Figure 2. Stress variation across awafer as a function of the ratio of innerand outer target magnetic field

REFERENCES[1]Milena Moeira, et.al., “Aluminum scandium nitride thin-film bulk acoustic resonators for wide band applications”,
Vacuum, July 2011, Issue 1, pp. 23-26[2]Morito Akiyama, “Influence of temperature and scandium concentration on piezoelectic response of scandium aluminum
nitride alloy thin films”, Applied Physics Letters, Oct. 2009, Vol.95, Iss. 16, pp. 2107-2107-3[3]H.P.Lobl, et.al.. "Piezoelectric materials for BAW resonator and filters", 2001 IEEE International Ultrasonics Symposium,
Atlanta, GA, Oct. 7-10,pp.807-811.
[4]Pau Muralt, et.al.. “Electromechanical properties of AlScN thin films evaluated at 2.5 GJz film bulk acoustic resonators”,
Applied Physics Letters 99, 2011[5]Keiichi Umeda1, et.al.. “Piezolecetric properties of ScAlN thin films for piezo-MEMS devices", MEMS 2013, Taipei,
Taiwan, January 20 – 24, 2013

IFCS-EFTF1-PAB1-6

High temperature perovskite-structured BiFeO3-PbTiO3Bi(Zn1/2Ti1/2)O3 piezoelectric ceramics
Jian Yu and Xianbo Hou
Functional Materials Research Laboratory, Tongji University, Shanghai 200092, China
Email: jyu@tongji.edu.cn
High temperature and high performance ferroelectric piezoelectric ceramics are striking strongly for
emerging high temperature applications of piezoelectric filters, sensors and actuators. Lead ZirconateTitanate (PZT) near the morphotropic phase boundary (MPB) dominates commercial piezoceramics but
has relatively low Curie temperature (TC) below 386oC. The BiFeO3-PbTiO3 (BF-PT) system wasreported to have TC ~ 632oC at its coexistent phase boundary (CPB) with around 32 at.% PbTiO3
content. Nevertheless, poor mechanical and insulating properties limit their piezoelectriccharacterizations and applications in the form of ceramics.
In this presentation, the authors demonstrated experimentally that adding Bi(Zn1/2Ti1/2)O3 (BZT) into
BiFeO3-PbTiO3 system makes their ceramics mechanically robust, owing to reduced negative thermal
expansion coefficient. Perovskite-structured BF-PT-BZT ternary solid solution keeps the CPB feature
but TC increases up to about 700oC. Systematical investigations showed that the CPB position, TC andpiezoelectric properties of BF-PT-BZT are closely dependent on the ceramic grain size, resulting fromdifferent processing and thermal treatments. A maximum piezoelectric property of TC = 560oC, d33 = 30
pC/N, 33T/0 = 302, and tan = 0.02 was obtained here for the CPB 0.53BF-0.32PT-0.15BZT ceramics
with average grain size about 0.3m, which is better than that of commercial K-15 piezoceramics: TC ~610oC, d33 = 18 pC/N, 33T/0 = 140, and tan ~ 0.03.
The La substitution effect on the lattice structure and piezoelectric properties of tetragonal 0.50BF0.35PT-0.15BZT ceramics was also studied. It was observed that the tetragonality of c/a ratio and TC
decrease but the piezoelectric properties increase with increasing La substitution. The enhanced
piezoelectric performance with La substitution was preferably attributed to the structural phase transition
fromtetragonal
into
coexistenttetragonal
andrhombohedral.
For
the
CPB
Pb0.35Bi0.625La0.025(Ti0.425Zn0.075Fe0.5)O3 ceramics poled at 140oC with 5 kV/mm DC electric field, a goodpiezoelectric property of TC = 497oC, ε33T/ε0 = 367 and d33 = 43 pC/N was obtained, which iscomparable with the commercial MLT piezoceramics with TC = 495oC, ε33T/ε0 = 170 and d33 = 51 pC/N.
Our experimental studies demonstrate that BF-PT-BZT ceramics exhibit not only good high temperature
piezoelectric properties but also better mechanical properties. In contrast to MLT and K-15 commercial
piezoceramics, BLF-PT-BZT provides a big space like the PZT to adjust piezoelectric performance andtemperature stabilities by changing composition near the CPB for applications of high temperaturefilters and sensors. Our essay is anticipated to excite new designs of high temperature and highperformance perovskite-structured ferroelectric piezoceramics and extend their application fields ofpiezoelectric transducers and sensors.

IFCS-EFTF1-PAB1-7

Optimization of tether geometry to achieve low anchor loss inLamé mode resonators
Vikram Thakar1 and Mina Rais-Zadeh1, 2
1

Department of Mechanical Engineering, University of Michigan, Ann Arbor, USA
Department of Electrical Engineering, University of Michigan, Ann Arbor, USA

2

Email: thakar@umich.edu
The quality factor (Q) of micromachined resonatorsin the sub-GHz regime is most often limited by theanchor loss (design dependent) rather than thefundamental material limitations1. In this work westudy the fundamental cause of anchor dissipationin Lamé or wineglass mode resonators and showthat by optimizing the resonator tether geometry, Fig. 1:(a) Resonator mode shape. (b) First two flexural
low anchor losses can be achieved76; thus, making modes of the tether. Tether width is 2 μm for both.
it possible to reach the intrinsic frequencyQ (fQ)limit of the resonator.
In order to support the Lamé mode resonance, thetethers are required to undergo forced flexuralvibrations. As a consequence the anchor loss insuch resonators is strongly dictated by theresonance frequency of the tether. When the tether
Fig. 2: Comparison of measured and predicted Q (withresonance frequency is close to the frequency of the anchor and phonon loss75 limit) as a function of tether
Lamé mode, the resonator Q is reduced due to the length for a tether width of 2 μm.
larger amount of energy lost from the tethers (Fig.
1). On the other hand, tether geometries having
resonances far from the Lamé mode frequency
show a higher anchor Q. To verify this hypothesis,
finite element analysis of the structures isperformed using COMSOL with anchor loss
estimated using the Perfectly Matched Layer(PML) approach (Fig. 2)77. For experimental
characterization, devices are fabricated on a lowresistivity SOI substrate with 1 μm actuation gaps
and released using backside DRIE. Both the Fig. 3: Measured response and a SEM image of a Lamé
simulation and measurement results for the mode resonator (tether width 2 μm, length 17.5 μm).
fundamental Lamé mode are found to corroborate
the presented hypothesis (Fig. 2). Using such an optimization technique, a high-Q Lamé mode resonator
operating in its fundamental mode at 41.5 MHz is demonstrated with a Q of 296,000 (in vacuum, at room
temperature and 300V bias). The fQ of the resonator is 1.23  1013, which is close to the fundamental limit
for silicon (Fig. 3)1. Note that the required bias voltage can be reduced by reducing the actuation gap.

75

R. Tabrizian, M. Rais-Zadeh and F. Ayazi, Transducers, 2009.

76

L Khine and M. Palaniapan, J. Micromech. Microeng., vol. 19, pp. 015017, 2009.

77

D. Bindel and S. Govindjee, Int. J Numer. Meth. Eng., vol. 64, pp. 789-818, 2005.

IFCS-EFTF1-PAB1-8

Mechanically Coupled SOI Lamé-Mode Resonator-Arrays:
Synchronized Oscillations with High Q Factors of 1 Million
Yuanjie Xu and Joshua E.-Y. Lee
Department of Electronic Engineering, City University of Hong Kong, Hong Kong SAR
Email: joshua.lee@cityu.edu.hk
In this work, we present the first demonstration of synchronized oscillations in an SOI resonator arraywith Q’s of 106 through mechanical coupling. Our experimental results indicate that even as the lengthof the array is expanded, Q is maintained at 106 (f-Q of 1.3×1013); close to that of a single Lamé
resonator. These results in turn suggest that mechanical coupling can be extended to even yet longer
arrays for improved transduction and power handling without diminishing Q.
Mechanically coupling resonators into
arrays for synchronized oscillation has been
demonstrated previously in CMOS
MEMS78 and PolySi79 to achieve reduced
motional resistance and increased power
handling.
However, till now no
mechanical-coupled array approaching the
f-Q limit of Si has been demonstrated. Herewe apply mechanical coupling to theisochoric Lamé mode where thermoelastic
damping is insignificant relative to anchor Fig. 20: FE simulation and micrograph (showing also theand Akhiezer effect loss.
transduction configuration) of a coupled 6-resonator array
An array of up to 6 resonators (each 320×320μm2) was fabricated using a standard SOI MEMS process.
To allow fully-differential capacitive transduction, the array is divided into 2 sections (Fig 1). The 3
resonators in each section are designed to resonate in phase using half-wavelength (λ/2) beam couplers.
Between the 2 sections, the vibration-combination is anti-phase through a full wavelength (λ) beamcoupler.
The devices were measured in vacuum using a
DC bias voltage Vdc of 50V and RF source
power of 0dBm. Fig. 2 shows the measured
electrical transmission of arrays of 6 and 4
resonators, including a single Lamé resonator(360µm). Q is the same between the two arrays,
and just slightly lower compared to the single
Lamé (1.2 million).
An increase in the
nonlinear bifurcation point could be observed
when increasing the array length.
Fig. 2: Measured transmission of a 6-resonator relative
to a 4-resonator array and single Lamé resonator
78

M.-H. Li, W.-C. Chen, S.-S. Li, “Mechanically coupled CMOS-MEMS free-free beam resonator arrays with enhanced
power handling capability,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 59, no. 3, pp. 346-357, Mar. 2012.
79

Y.-W. Lin, S.-S. Li, Z. Ren, C. T.-C. Nguyen, “Low phase noise array-composite micromechanical wine-glass disk
oscillator,” Tech. Dig. IEEE Int. Electron Devices Mtg., Washington, DC, Dec. 5-7, 2005, pp. 287-290.

IFCS-EFTF1-PAB1-9

A Parallel-Class Thermally-Actuated Micromechanical Filter with
Tunable Center Frequency and Bandwidth
Cheng Tu, Joshua E.-Y Lee
Department of Electronic Engineering, City University of Hong Kong, Hong Kong
Email: mems305@gmail.com
In this paper, we report the very first thermally-actuated micromechanical filter. As a proof of concept,
the filter has a modest center frequency of 64 MHz, which in principle can be scaled to yet higher
frequencies. Resonators using thermal actuation and piezoresistive readout (thermal-piezoresistive
resonators) have attracted much interest owing to a promising frequency-scaling characteristic in termsof electromechanical transduction and the simplicity in fabrication80; but they also suffer fromsubstantial direct resistive coupling between the input and output ports. By using a parallel-classconfiguration81 applied to a pair of these resonators, feedthrough cancellation can be achieved while
simultaneously realizing a 2nd-order high stopband rejection filter.
Fig. 1 shows SEMs of a pair of dog-bone shaped twin resonators fabricated side-by-side on the same dieusing a standard SOI MEMS process. Also shown is the circuit schematic to realize a parallel-classfilter. Both resonators are electro-thermally excited by the same AC drive voltage, but their output
motional currents are sensed differentially. A slight mismatch between their resonant frequencies results
in a bandpass filter frequency response. Since the resonant frequencies of each resonator can be can betuned by adjusting the bias voltage due to the Joule heating effect, their separation and thus the
bandwidth of the filter can be tuned as shown in Fig. 2 (from 0.004% to 0.002%). The center frequencyof the filter is also tunable by the same effect (72.2ppm tuning range achieved so far). The out-of-band
rejection is more than 10dB. It should be noted that the response shown in Fig. 2 was measured without
proper termination, but still showing very little ripple in the passband (<1dB). These results further
highlight the applicability of thermal actuation to high frequency applications to now also include evenfiltering.

Fig. 21: Circuit schematic for the parallel classfilter with SEMs of two 64MHz 10-μm-thick dogbone resonators fabricated using a standard SOI
MEMS process.

Fig. 2: Measured electrical transmission of thefilter. Vb2 is varied to demonstrate tuning of the
bandwidth while Vb1 is kept constant at 3.52V.

80

A. Rahafrooz, S. Pourkamali, “High-frequency thermally actuated electromechanical resonators with piezoresistive
readout”, IEEE Trans. Electron Devices, vol. 58, p. 1205-1214, 2011.
81

S.-S. Li, Y.-W. Lin, Z. Ren, C. T.-C. Nguyen, “A micromechanical parallel-class disk-array filter”, Proceedings of 2006
IEEE Int. Frequency Control Symp., Geneva, Switzerland, May 29-June 1, 2007, pp. 1356-1361.

IFCS-EFTF1-PAB1-10

Anomalous DC-Current-Induced Attenuation of Q Factor in a
Silicon Contour Mode Micromechanical Resonator
Haoshen Zhu, Cheng Tu and Joshua Lee
Department of Electronic Engineering, City University of Hong Kong, Hong Kong
Email: haoshezhu2-c@my.cityu.edu.hk
Micromachined silicon resonators have the advantage of employing intrinsic gain in the form ofpiezoresistive sensing82 or a resonant body transistor83 to enhance electromechanical transduction. Thisentails applying a DC bias current through the resonator. In this paper, we show that simply applying a DC
current for such a purpose could significantly reduce the quality factor (Q) given the right combination of
conditions such that the thermal and elastic
eigenmodes overlap.
We applied a DC bias current ranging from 1mA to
20 mA through a single-crystal-silicon square plate
resonator vibrating in the square extensional (SE)mode for piezoresistive sensing with capacitive
drive. Self-heating due to the bias current causes theresonant frequency to shift, which we have modeledusing finite element simulation.
Unreported
elsewhere, Q was found to drop by more than halfaround a precise bias current level as shown in Fig.
1. By fine tuning the bias current around 15mA, it isfound that the peak height decreases while the -3dB Fig. 22: Q vs. bias current profile of an 800μm wide
bandwidth notably widens as the bias current is SE-mode resonator aligned along the <110> crystal
tuned closer to a precise bias point given by axis. Significant Q drop is detected around 15mA.
15.246mA. This effect appears to be symmetric
about this biasing (Fig 2). It can be further notedthat the original single peak splits to two peaks at
this bias point.
To rule out its causal relation to piezoresistive
electromechanical coupling, we have repeatedmultiple measurements using capacitive sensing
with a heating current through the device.
Resonators of different dimensions and orientations
were also measured, all confirming the same trends. Fig. 2: Measured transmission of resonator as theThis effect is believed to arise from thermo-elastic bias current is fine-tuned around 15mA (highlighted
coupling. Due to the temperature dependence of by red box in Fig. 1), showing the transition of Q.
silicon’s elasticity, self-heating due to bias current
causes the mechanical frequency to shift. As the elastic and thermal modes overlap, thermo-elastic
damping84 is magnified, thus leading to a significant drop in Q.

82

J. T. M. van Beek, et al., IEEE IEDM 2007, pp. 411–414.

83

D. Grogg, et al., IEEE IEDM 2008, pp.1-4.

84

A. Duwel, et al., JMEMS, vol. 15, no. 6, pp. 1437-1445, 2006.

IFCS-EFTF1-PAB1-11

Multimode Characteristics in Mechanically-Coupled
Silicon Carbide (SiC) Nanowire Array Resonators
Rui Yang1*, Jaesung Lee1, Zenghui Wang1, Philip X.-L. Feng1*
1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
Email: rui.yang@case.edu, philip.feng@case.edu

85

A

0.1
0.0
-0.1

(a)

B

0.4

A

C

0.30

0.5

B

D

C

0.24

0.3

0.25

0.4

0.22

0.2

0.20

0.3

0.20

3.7 3.8

5

0.15

6

7

8.2

D

0.22
0.21

E

0.4

from

0.20

0.2

0.1

E

S1/2
(pm/Hz1/2)
x

0.2

S1/2
(V/Hz1/2)
V

Figure 1a shows measured multimode response
an array of 10 SiC NWs with individual
dimensions
Lwt10µm50nm50nm.
Sensitive detection of mechanical displacement
down to the levels of Brownian motions of thedevices is achieved by using a laserinterferometer with ~1μm spot size and pm/Hz
displacement sensitivity (on SiC NWs). We
directly map the mode shapes with high spatial
resolution, and compare the results with finite
element modeling (COMSOL, Fig. 1).
Mechanical coupling (via the clamping plate)
suppresses the natural modes of each individual
NWs, while enabling the system to exhibit newcollective resonances. Probing the characteristics
the coupled modes and degeneracy allows us todetermine and further engineer the couplingstrength, toward higher performance SiC NEMS
arrays for specific applications85,86,87.
By
carefully examining the resonance characteristics
their scaling laws with array size (N, number ofNWs), we advance this SiC device technology as
platform,withsensitive
optomechanicaltransduction, for studying new phenomena inlarge-N systems, from chaos to synchronization.

S1/2(V/Hz1/2)
V

We report measurements and modeling of arrays of mechanically-coupled very thin SiC nanowire (SiC NW)
nanomechanical resonators. The exceptional mechanical properties and very attractive optical properties of
SiC make it highly interesting for nanoelectromechanical systems (NEMS) and optomechanical devices, withresonant modes operating at high frequencies that can be exploited for resonance-based signal processing andsensing applications. In this work, we demonstrate arrays consisting of SiC NWs as narrow as 50nm
(patterned by electron beam lithography on a
0.5
~50nm SiC epilayer) and investigate the0.4
multimode resonances in mechanically coupled
0.6
0.3
arrays.

8.4

0.18
12.0 12.2

10Frequency (MHz)

0.19
0.18

14 15

0.2

15

(b)

(e)

(c)

(f)

SiC
of

(d)

(g)

Fig. 1: (a) Resonance spectrum measured froma SiC NW array of N=10. Insets: first 5
measured resonances (A-E) with fitting
indicated by the red dashed line. (b)-(g):COMSOL simulation of the first 6 coupledmodes of the array of 10 SiC NWs. Insets:
cross-section views of the mode shapes.

andaS. Lee, C.T.-C. Nguyen, “Mechanically-coupled micromechanical resonator arrays for improved phase noise”, Proc. IEEE
Int. Freq. Contr. Symp. (IFCS 2004), pp. 144-150 (2004).
86
D. Weinstein, et al., “Mechanical coupling of 2D resonator arrays for MEMS filter applications”, Proc. IEEE Int. Freq.
Contr. Symp. & Euro. Freq. & Time Forum (IFCS-EFTF 2007), pp. 1362-1365 (2007).
87
G.K. Ho, R. Abdolvand, F. Ayazi, “Through-support-coupled micromechanical filter array”, Proc. 17th IEEE Int. Conf. on
MEMS (MEMS 2004), pp. 769-772 (2004).

IFCS-EFTF Group 2 poster session 1
Forum Hall
Monday & Tuesday, July 22-23, 2013, 01:00 pm - 02:00 pm and 3:30 pm - 4:30 pm
Chair:

Fabrice STHALFEMTO-ST

IFCS-EFTF2-PAB2-1

Study of Phase Noise in VCXO with Inversion-Mode Varactors
Yao Huang Kao and Teh Chau Liau
Department of Communication Engineering, Chung Hua University, Hsinchu Taiwan
Email: yhkao@chu.edu.tw
Voltage controlled crystal oscillators (VCXO) play an essential role in modern communication as
reference sources in local oscillators. In this application the stringent request of phase noise and widetuning are needed. The VCXO is normally built by CMOS process due to low cost and the capability of
total integration. For simplicity, the MOS varactor in inversion mode is often employed to change thefrequency. However, the capacitance measured in small-signal approach appears a step-like shape,
which is not obvious for wide tuning application. In this abstract, the tuning behavior and related phasenoise in large-signal operation is investigated.
According to the Leeson’s model, phase noise is inversely proportional to signal power. In our design,
the signal magnitude is maximized to have rail to rail swing. The dimension of varactor is traded off
between tuning ratio and quality factor. Under TSMC standard 0.35um mixed-mode process with 2P4M
and Polycide, the dimensions of width W, channel length L, and finger number m are chosen as
W  L  m  30 1  40 , respectively. The varactor encounters different modes of strong inversion anddepletion. The partition depends on the tuning voltage. The value of capacitance is predicted from
Fourier analysis of I-V waveform. The wiring and C-V characteristic of inversion mode are shown in
Fig. 1a and Fig. 1b, respectively. The slope is steep at small swing and becomes slanted as the swing isincreased.
The performances of tuning capability in the typical Pierce oscillator with power supply VDD=3V areshown in Fig. 2a. The linear tuning range is obtained from zero to 1.8V with deviation is from -30 to+20ppm, respectively. Above 1.8V the tuning is saturated. The slope is maximized at 0.8V with roughly
equal duration in inversion and depletion. The corresponding phase noises are also illustrated in Fig. 2b.
The worst case -80dBc@10Hz offset occurs at the point with maximal tuning slope. At both ends withsmaller slopes the phase noises becomes better -90~-100 dBc@10Hz offset. The measured tuning
capability matches well with the prediction under large-signal swing.
Vtune

VG

D

G

S

B

n+

n+

VG

gnd
p+

gnd

P-sub

Vtune

(a)
Varactor Capacitance (pF)

Fourier analysis method
6
5.5
5
4.5
4
3.5
3
2.5
2
1.5
1

1.5V
1.0V
0.5V
small
dc

0

0.5

1

1.5

2

2.5

3

Vtune (volts)

(b)
(a)
(b)
Fig. 1 NMOS varactor in (a) Inversion mode Fig. 2 (a) Measured frequency deviation and slope and (b)and (b) C-V curves
phase noises at offset 10 and 100Hz

IFCS-EFTF2-PAB2-2

A low-phase-noise 4.72-5.58-GHz LC-VCO design
Yung-Hsiang Ho1 and Chia-Yu Yao2
Department of Electrical Engineering, NTUST, Taipei, Taiwan
Email: 1D9807403@mail.ntust.edu.tw, 2chyao@mail.ntust.edu.tw
For the application requiring a high frequency andgood phase noise performance, the LC-tank VCO ispopular in VCO design. In order to have a small VCO
gain, the LC-tank VCO usually has a capacitor array
across the VCO’s differential outputs as the coarse-tuning
stage for the band selection.
Fig.1 shows the proposed LC-tank VCO schematic. It
uses a PMOS cross-coupled pair to mimic a negative
resistor. The varactors Cj1-Cj2, two shunt capacitors Cf1Cf2, the capacitor array, and the inductor L form theresonator of the VCO. The current on Rc contains evenorder harmonics. These harmonics mixing with the VCO’s
output produces an in-band noise. This in-band noise
makes the VCO’s phase noise even worse. The proposed
VCO utilizes a capacitor Cc across Rc to suppress the
harmonics. In addition, we use two capacitors Cf1 and Cf2
across M1 and M2, respectively, to serve as a filter toreduce the amplitude of the harmonics. Let v1 = vcom + vm
sin t and v2 = vcom – vm sin t. We can obtain
{

[(

)

]

[(

)

]

[(
{
[(

Fig. 2: The small-signal model of VCO’s upper part.
R &S F S U P S i gna l S o urc e A na l y ze r])

S ettings])

Fig. 23: The proposed LC-tank VCO.

5 .1 7 4 7 9 9 G H z

I nt P H N (1 0 0 .0 .. 1 .0 M ) -6 8 .7 dBc

Signal L evel:-2 6 .8 8 dBm

Res idual P M

2 9 .9 0 5 m°

P L L M ode

H armonic 1

Res idual FM

7 9 .5 8 6 H z

RM S Jitter0 .0 1 6 1 ps

I nternal Ref T uned

LO C KE D

R e s i d u a l N o i s e [T 1 w/o s p u r s ]Signal Frequenc y:

I nternal P has e D et

P h a s e D e t e c t o r +2 0 d B

P has e N ois e [dBc /H z]

M arker 1 [T 1 ]M arker 2 [T 1 ]M arker 3 [T 1 ]M arker 4 [T 1 ]RF A tten

1 kH z1 0 kH z

1 0 0 kH z

1 MHz

-1 1 8 .9 1 dBc /H z

-1 3 7 .1 2 dBc /H z

-1 4 0 .2 8 dBc /H z

-1 4 0 .2 9 dBc /H z

0 dB

T op -8 0 dBc /H z
UNCAL

LoopBW

[ (

)

(

)]

-90

2 CLRW R

where Vdc = vcom – vt. Fig. 2 shows the small-signal circuit
model of the VCO’s upper part where Zc = Rc // Cc. The
capacitors Cf1 and Cf2 in parallel with Zc serve as a filter
for the even-order harmonic signals at vs.
The VCO was realized in TSMC 0.18 m CMOS
process. Fig. 3 shows the measured phase noise of the
VCO output tuned at 5.17 GHz. The phase noise is –137.12 dBc/Hz at 10-kHz offset frequency. The measured
rms jitter is 2.072 ps at 5.428-GHz output. The power
consumption is 10 mW at 1.8-V supply voltage.

A

1 CLRW R
SMTH 1%

-100

-110

1

SPR OFF
TH 0dB

-120

-130

2
3

4

-140

100 Hz

1 kHz

10 kHzFrequency Offset

100 kHz

1 MHz

M eas urement A borted

PLL1-vc0.7-vB0.7-f10.3g-pn108-Vc
Date: 7.JAN.2013

00:06:17

Fig. 3: Measured phase noise at 5.17 GHz.

This work is partially supported by the National Science Council of Taiwan under grant NSC 101-2221-E-011168.

IFCS-EFTF2-PAB2-3

Using 2-Bit Counter to Predict the Starting SAR Bit for a FastLocking Wide-Range All-Digital DLL
Yung-Hsiang Ho1 and Chia-Yu Yao 2
Department of Electrical Engineering, NTUST, Taipei, Taiwan
Email: 1D9807403@mail.ntust.edu.tw, 2chyao@mail.ntust.edu.tw
Among various digital delay-locked loops (DLLs), thesuccessive approximation register (SAR)-based DLL is
promising because it provides better tradeoff among
hardware area, delay resolution, and lock time.
Assume that the time delay introduced by the digital
controlled delay line (DCDL) is linearly varied with the
SAR code. If a SAR bit is set to high, the delay of the
DCDL will increase by a half of the delay amountcorresponding to the previous significant bit. Thus, if we
can estimate the current delay of the DCDL, we canpredict the starting bit from which the SAR search canbegin with to shorten the lock time of the DLL.

Fig. 24: A timing example when SSARBP

starts form the (M-1)th bit.
In order to explain the proposed
starting
SAR-bitprediction(SSARBP)method,somenotations are shown in Fig. 1. Let
Tclk denote one clock cycle, Tint
represent the intrinsic delay of thedelay line, and Td[m] , m = 0, 1, …,
M, represent the excess delay ofthe delay line caused by setting themth bit of the control code to logic(a)(b)
high. As mentioned before, Td[m] = Fig. 2: (a) The measured SAR code in the lock-in process for a 120-MHz
2Td[m – 1]. In this paper, we assume
input clock. (b) The measured jitter for a 1-GHz input clock.
that the control code for the DCDL
has M + 1 bits.

In the proposed DLL, we divide the input clock (CLKin) frequency by two as the clock signal(CLKcounter) for the counter. Fig. 1 shows an example timing diagram. In the beginning of an SSARBP
cycle, we reset the DCDL first. After Tint, the counter starts to count. We then monitor the DCDL output
signal CLKout. When the rising edge of CLKout is observed, the counter value at that moment gives the
DCDL delay information. We can use the information to adjust the SAR code. The DLL circuit was
implemented in TSMC 0.18 m CMOS process. The measured results show that the proposed circuit
can operate from 66 MHz to 1 GHz. The lock time is within 17-23 clock cycles. Fig. 2(a) shows that thelock time is 20 clock cycles for a 120-MHz input clock. Fig. 2(b) shows that the rms jitter is 1.881 ps for
a 1-GHz input clock.
This work is partially supported by the National Science Council of Taiwan under grant NSC 101-2221-E-011-168.

IFCS-EFTF2-PAB2-4

Low phase noise microwave analog optical link performance
study for high dynamic environment platform

Jean-Marc LESAGE1, Mathieu LE PIPEC1
1

DGA – Information Superiority, DGA French MoD, Bruz, France
Email: jean-marc.lesage@dga.defense.gouv.fr

Distribution of very low phase noise and low spurious microwave Local Oscillator (LO) is needed formost of the radar or electronic warfare applications. In this paper we study the capability to optically
carry low phase noise LO, thanks to a directly-modulated optical link1, while subjected to severe
environmental conditions. First the optical link is compared to a coaxial cable link in terms of additive
phase noise subsequently the absolute amplitude and phase noise under random vibration are compared.
Firstly, it should be noticed that even in case of a wide band optical link, the phase noise floor difference
between optical and coaxial cable is small even for short distance links. Secondly, the absolute
amplitude and phase noise of the optical and coaxial cable link are measured with the entire optical linkor only with some piece component of the link (10 GHz LO, optical fiber, laser and photodiode) under
random vibration. The phase noise degradation is almost the same when the optical or the coaxial link isunder vibration and the main degradation is always due to the Local Oscillator whatever the technology
is (OEO : Opto-Electronic Oscillator, quartz,…; some ways of improvement of optical link g-sensitivity
that can be useful for OEO2 will be
discussed). Thanks to recent
experimentations done by DGA, it has
been shown that very low phase noise
microwave LO signals can be carriedon optical link without any phase noise
degradation due to the link while
subjected to random vibration.
-20
-30
-40
-50
-60

L(f) dBc/hz - 10 GHz

-70

1

-80
-90

-100
-110
-120
-130

M.Chtioui et al “Analog microwave
-140
-150
photonic link based on a high power directly-160
modulated laser, a high power photodiode and-170
passive impedance matching”, Microwave-180
1,00E+01
1,00E+02
1,00E+03
1,00E+04
1,00E+05
1,00E+06
1,00E+07
Photonics 2012.
Offset fequency (Hz)2
D. A. Howe et al “Active Vibration-induced
LO after optical link
LO after coaxial cable link
LO only
PM Noise Control in Optical Fibers: Preliminary
LO after coaxial cable under vib
LO after optical link under vib
LO under vib only
Studies”, IEEE 2007
Fig. 25: Phase noise of the optical and coaxial cable links with all the
Acknowledgements: The directly modulated
links or only part of them under random vibration
optical link, designed by TSA in the frame of
the DGA-funded project ORGE, use semiconductor DFB laser diode and MUTC photo-diode, designed by 3-5 Lab andpackaged by 3S Photonics.

IFCS-EFTF2-PAB2-5

Evaluation of the accuracy of the method for measuring state-ofthe-art ultra-high stability quartz crystal oscillators
Patrice Salzenstein1, Alexander Kuna2, Frédéric Lefebvre3
1

Franche Comté Electronique Mécanique Optique Thermique Sciences et Technologies (FEMTO-ST),
Centre National de la Recherche Scientifique (CNRS), Besançon, France
2
Intitute of Photonics and Electronics (IPE), Academy of Sciences, Prague, Czech Republic
3
Oscilloquartz, Neuchâtel, Switzerland
Email: patrice.salzenstein@femto-st.fr and kuna@ufe.cz

The best frequency stability ever measured on a quartz crystal oscillator was recently obtained. This new
Boitiers à Vieillissement Amélioré (BVA) oscillator has an estimated flicker frequency modulation(FFM) floor as lower as 2.5x10 -14 at 5 MHz88,89. It leads to a significant step. To achieve such a low
FFM floor, we assume that best resonators are fully characterized90 and packed. It was obtained using adouble rotated SC-cut quartz with low phase noise, good aging characteristics and low sensitivity todrive level dependency placed in appropriate thermostat in the first prototype of a double ovencontrolled crystal oscillator (OCXO) realized in Switzerland by Oscilloquartz company. We checkedthat the ultra-stable signal delivered by such a BVA oscillator can be distributed without any
degradation of its short term stability91. It has to be underlined that precise measurements on oscillators
were carefully performed at the Time and Frequency department in Prague in very favorable
environmental conditions and deduced by three cornered hat analysis 92,93,94,95 on a dedicated system96.
Our process for short term is analogous to what occurs for long term frequency stability characterization,
but could provide questionably a precise determination of FFM floor. The analysis proceeds bymatching the theoretical and the best experimental curves not exactly simultaneously. In this paper we
discuss the accuracy of our method.

P. Salzenstein, A. Kuna, L. Šojdr and J. Chauvin J., "Significant step in ultra high stability quartz crystal
oscillators", Electronics Letters, 46(21), 1433–1434, (2010).
A. Kuna, J. Cermak, L. Šojdr, P. Salzenstein and F. Lefebvre, "Lowest Flicker-Frequency Floor Measured on BVA
Oscillators", IEEE Trans. on UFFC 57(3), 548-551 (2010).
P. Salzenstein, A. Kuna, L. Šojdr, F. Sthal, N. Cholley and F. Lefebvre, "Frequency stability measurements of ultrastable BVA resonators and oscillators", Electronics Letters, 46(10), 686-688 (2010).
P. Salzenstein, N. Cholley, A. Kuna, P. Abbé, F. Lardet-Vieudrin, L. Šojdr and J. Chauvin, "Distributed amplified
ultra-stable signal quartz oscillator based", Measurement, 45(7), 1937–1939 (2012).
92

J. E. Gray and D. W. Allan, "A Method for Estimating the Frequency Stability of an Individual Oscillator," Proc. ofthe 28th Ann. Symp. on Freq. Contr., May 1974, pp. 243-246 (1974).
93

D. W. Allan, "Time and frequency (time domain) characterization, estimation, and prediction of precision clocks
and oscillators," IEEE Trans. on UFFC, 34(6), 647–654 (1987).
94

P. Tavella and A. Premoli, "Estimation of Instabilities of N Clocks by Measuring Differences of their Readings",
Metrologia, 30(5), 479-486 (1993).
95

F. Vernotte, M. Addouche, M. Delporte and M. Brunet, "The three cornered hat method: an attempt to identify someclock correlations", IEEE Freq. Contr. Symp., 23-27 Aug. 2004, pp. 482- 488 (2004).
96

G. Brida, "High resolution frequency stability measurement system," Rev. Sci. Instrum., 73(5), 2171–2174 (2002).

IFCS-EFTF2-PAB2-6

Measurements of Intrinsic Phase Fluctuations in a Cryogenic
Microwave Amplifier
Romain Bara-Maillet1, Stephen R. Parker1, Eugene N. Ivanov1, Jean-Michel Le Floch1, Michael E.
Tobar1
1
ARC Centre of Excellence for Engineered Quantum Systems, School of Physics, The University ofWestern Australia, Crawley, WA/Australia
Email: barar01@student.uwa.edu.au
There has been a continuous interest in the development ofcryogenic microwave amplifiers with low level of phase noiseand power dissipation for fundamental physics experiments.
For example, such amplifiers have enabled accuratecharacterization of electromagnetic properties of ultra-high Q
electromagnetic resonators at single photon energies97. They
are also crucial for experiments on the coherent manipulationof spin qubits with implications to quantum computing2. We
Fig. 26: Experimental setup.
studied the phase noise properties of a low noise X-band
cryogenic amplifier (LNF LNA7-10) both at room and cryogenic temperature. The amplifier was placedin a temperature-stabilized environment to minimize the influence of ambient temperature on the phasedelay of the transmitted signal. By utilizing both the time and frequency domain techniques wemeasured amplifier phase noise spectra at Fourier frequencies from tens of μHz to 1 MHz. At room
temperature, the noise measurements were conducted with a mixer-based phase bridge, Fig. 1. The
bridge was placed on a temperature-stabilized plate inside a vacuum chamber, Curve 1 in Fig. 2 shows
the phase noise floor of the thermally isolated phase bridge as a function of Fourier frequency F. It can
be closely approximated by 4 10-13 / F + 2 10-18 / F3 (rad2/Hz). The cubic term in the above fit dominates
the noise floor at F<1 mHz. It reflects the residual effect of ambient temperature fluctuations on the
spectral resolution of the phase bridge. For comparison, the noise floor of the “exposed” phase bridge islimited by ambient temperature fluctuations at F<1
Hz. Curve 2 in Fig. 2 shows the phase noise
spectrum of the LNA at 9 GHz with -34 dBm input
power. It has a rather unusual 1/F1/2 dependence inthe frequency range 20mHz<F<200Hz. At F<1
mHz, amplifier phase noise is proportional to 1/F3,
which can be attributed to fluctuations of theambient temperature. The discussion on phase noiseproperties of the above amplifier at 5 Kelvin isbeyond the scope of this Abstract and will bepresented at the Symposium.
Fig. 2: Phase noise spectra at ambient temperature
1

D. Reilly and J. Colless, “Cryogenic high-frequency readout and control platform for spin qubits”, Rev. Sci. Instrum. 83,
023902 (2012); doi: 10.1063/1.3681195
2

D. Creedon, Y. Reshitnyk, W. Farr, J. Martinis, T. Duty and M. Tobar, “High Q-factor sapphire whispering gallery mode
microwave resonator at single photon energies and millikelvin temperatures”, Appl. Phys. Lett. 98, 222903 (2011)

IFCS-EFTF2-PAB2-7

VERY LOW POWER CONSUMPTION, ULTRA LOW PHASE MOISE, MINIATURE CONVENTIONAL OCXO

R. Boroditsky, J. Gomez,
NEL Frequency Controls, 357 Beloit Street, Burlington, WI 53105
Battery powered equipment, whether instrumentation, underwater exploration, or military require highperformance frequency sources with very low power consumption for obvious reason. Current state of
the art in the area of very low power consumption OCXO [1], [2] employs evacuation of the entire (oralmost entire) electronic circuit with crystal resonator in metal enclosure and internally heating thecontent. Although achieving the goal of significant reduction in power consumption (60 – 80 %), thisapproach has some serious drawbacks. The phase noise performance of one of the implementations isaverage at best, of another - is outright poor. Evacuation of the entire OCXO requires very complex andtedious processes, since any minute contamination can destroy deep vacuum, needed for device tooperate. The availability of die semiconductor components, a necessity for inside the vacuum, is very
limited. The devices are susceptible to exposure of elevated temperatures, which might induce internal
outgassing and deterioration of vacuum level. The goal of this work was to create a device, which would
eliminate above mentioned drawbacks i.e. employ conventional heating technique, use off-the shelfwidely available components, have comparable to evacuated devices power consumption and size, andexhibit superior phase noise performance. The goal was achieved by implementing special thermal
insulation technique, and NELs ULPN technology in 20x20x10 mm package. While the steady state
power consumption at room temperature is less than 250 mW, the phase noise at 10 Hz offset at <-145
dBc/Hz is better by 20 to 45 dBc than published specifications, and at -174 dBc/Hz, by 10 to 30 dBc on
the floor.

IFCS-EFTF2-PAB2-8

Phase Group Characteristic Based Frequency Measurement
Method with Wide Band and Fast Response
Shaofeng Dong, Wei Zhou, Wei Hu, Jinsong Zhan
Department of Measurement and Instrument, Xidian University, Xi’an, China
Email: shaofengdong@126.com
As the rapid development of frequency standard, the need arises to measure frequency in a wide band with a
Nx

f2

Gate

fx

Counter

Reshape

f1

Phase

f0

fout

Reshape

Data
Processing

Generating
Gate

Coincidence
Detection

N0

Phase group

Phase group

Gate

CounterFig. 2: Wide-band frequency measurement method.
high resolution. Restricted by the influence of  1
counting error, the resolution of the existing frequency measurement method is hard to improve.
Fig. 1: Variation rule of phase group.

By analyzing the phase variation rule between every two periodic signals with different frequency, as shownin Fig. 1, the phase group characteristics, such as phase group synchronization, are revealed in the paper.
With these characteristics, the direct measurement and comparison of periodic signals with different
frequencies in a wide band with a high resolution can be realized.
In this method, as shown in Fig. 2, two adjacent phase coincidence points of the reference frequency f 0 andthe measured frequency f x are used to generate the measurement gate. Because f 0 and f x are synchronizedstrictly with the start and stop signals of the gate,  1 counting error can be eliminated. In gate time, the

Nx
. If
N0
there is a multiple relationship between f 0 and f x , it takes a long time to generate the measurement gate.
Fine phase shift is used on the reference frequency to shorten the measurement time.
counting numbers of f x and f 0 are N x and N 0 , respectively, thus the measured frequency f x  f 0 

10MHz frequency measurement

Gate time: 0.01s

10000001.000000
10000000.800000
10000000.600000
10000000.400000
10000000.200000
10000000.000000
9999999.800000
9999999.600000
9999999.400000
9999999.200000
9999999.000000
1

5

9

13

17

21

25

29

33

37

41

45 49
t/ s

53

57

61

65

69

73

77

81

85

89

93

97 101

Fig. 3: Experiment of frequency measurement at 10MHz.
Experiment results show, the method achieves a precision higher than 1×10-13/s in frequency comparison, as
shown in Fig. 3, the typical precision of signal from 30 kHz to100MHz achieve 6~8×10-12/s. With the
improvement of phase coincidence detection resolution, phase shift precision and component response speed,
the precision of this method can be further improved.
Supported by the Fundamental Research Funds for the Central Universities No. K5051204003, theNational Natural Science Foundation of China under Grant No. 10978017.

IFCS-EFTF2-PAB2-9

Event Timing Device Providing Subpicosecond Precision
Petr Panek1, Jan Kodet2,3, Ivan Prochazka2
1

Institute of Photonics and Electronics, AS CR, Chaberska 57, 182 51 Prague, Czech Republic
2
Czech Technical University in Prague, Brehova 7, 115 19 Prague, Czech Republic
3
Technische Universität München, Station Wettzell, 93444 Kötzting, Germany
Email: panek@ufe.cz

We are reporting on the latest experimental results achieved with an event timing device using a surface
acoustic wave filter as a time interpolator98. During tests of the first prototype, the dominant source ofthe measurement error was identified to be caused by noise of the filter excitation99. Therefore a newconcept of the excitation for the next version of the device was designed. The exciter is activated just fora very short period keeping the energy of the noise at the input of the filter as low as possible. Thissolution led to considerable improvement of the device performance.
It results from the experimental measurements that the single shot precision is repeatedly lower than
500 fs RMS when time marks generated synchronously with the time base are measured. The behaviorof the observed fluctuations can be well described as white noise with Gaussian distribution. Resulting
precision is in an agreement with the error budget based on the theoretical analysis.
When asynchronous time marks are split into two event timers and the resulting time difference ismeasured, the single shot precision is below 700 fs RMS per channel. In this case the measurement isaffected not only by random errors, but also by non-linearity of the time interpolation. Harmonic
distortion in the analog-to-digital converter has been identified as the main source of this additional
error. The time interpolation error is a periodic function of the time mark position. This dependence
oscillates very quickly in comparison to the clock period100.
The temperature dependence is below 0.1 ps/K. Operating the device in a common laboratoryenvironment without temperature stabilization, the stability TDEV better than 3 fs has been routinely
achieved for range of averaging intervals from 10 s to several hours.
The event timers are capable of stand-alone operation or they can create a net of timing units distributedin an area where unified time is kept using optional Two-Way Time Transfer modules101.

98

P. Panek, “Time-interval measurement based on SAW filter excitation”, IEEE Trans. Instrum. Meas., vol. 57, p. 25822588, 200899

P. Panek, I. Prochazka, ”Time interval measurement device based on surface acoustic wave filter excitation, providing 1 ps
precision and stability”, Rev. Sci. Instrum., vol. 78, p. 094701-4, 2007
100

I. Prochazka, P. Panek, "Nonlinear effects in the time measurement device based on surface acoustic wave filter
excitation", Rev. Sci. Instrum., vol. 80, p. 0761021-3, 2009101

P. Panek, J. Kodet, I. Prochazka, "Accuracy of two-way time transfer via a single coaxial cable", Metrologia, vol. 50,
p. 60-65, 2013

IFCS-EFTF2-PAB2-10

Background, Motivation and Objective:
Today, millions of FBAR Filters and Duplexers are sold into cell phones every year. The all-silicon
package used to package these filters (providing both package integrity and hermeticity) has beenutilized for the past 10 years and, to date, no part has been returned for compromised integrity or
hermeticity failures. The lid wafer in the all-silicon package has, until recently, only been used toprovide through-Si vias from the FBAR filter to the outside pads. The addition of circuitry to the lid
enables a host of new applications. Examples include the integration of SOI switches for advanced filter
switch modules, or the integration of SiGe LNAs with filters to provide extremely compact
filter/amplifier functionality. Our first application, however, is the integration of oscillator circuitry witha temperature-compensated FBAR resonator. The resulting chip-scale oscillator produces a single, welldefined frequency, and is highly sensitive (on the parts-per-million level) to package hermeticity. This
allows for the design and optimization of a robust package for yield and performance, and for the testingof new markets not dominated by filtering.
Statement of Contribution and Methods:
We present a fourth- design generation Free Running Oscillator and Voltage Controlled Oscillator using
integrated bipolar circuitry in the lid wafer with a temperature-compensated FBAR resonator in the basewafer. The goal is to produce a high frequency, low-noise oscillator. Because there are over 15,000
oscillators per wafer, we can develop very sensitive testing procedures to study the oscillator behavior.
We have determined our frequency measurement accuracy and precision to be ~ 0.2 parts-per-million,
and our phase sensitivity floor to be less than -175 dBc/Hz. Tests of package hermeticity completed todate suggest that the oscillators behave with the same level of integrity as our standard FBAR filters.
Results/Discussion:
The goal of this program is to demonstrate a robust, repeatable, chip-scale oscillator with superior
performance. We have measured tens of thousands of oscillators and observe a mean jitter performance
between 12kHz and 20MHz of 7.5 femto seconds. Output power is 2.4 dBm and the output drives 100 differential. The mean phase noise of the 2608 MHz oscillator at 800 kHz offset is -158 dBc/Hz and themean at 10 kHz offset is -118 dBc/Hz. The device draws 18.8 mA at 3.3V, and the phase noise at all
frequency offsets stays within 1 dB over the temperature range from -40 to 120°C. We see a 1 to 1
correlation between resonator Q improvement and close-in phase noise: a 15% improvement in Q
between two wafer lots improves close-in phase noise by 1.2 dB. Far from carrier noise is set by thepower delivered to the resonator. Due to the ability of the resonator to remain linear at high powers, wehave seen far-from-carrier phase noise as low as -174 dBc/Hz. The sensitivity to acceleration of theseoscillators is on the order of 1 ppB/g and the start up time is measured to be less than 10 μsec.

IFCS-EFTF2-PAB2-11

The Measurement of Transient Stability With High Resolution
Lina Bai, Wei Zhou, Zongqiang Xuan, Qinglan Zhang
Dept.of Measurement and Instrument, Xidian University. Xi’an, 710071, P.R.China
Measuring transient noise and short-term stability of signals with the digital counting methods isvery difficult. Transient stability plays an important part in the characterization of phase noise of signal
with high resolution.
With counting measuring method, the measuring gate is usually formed from 1ms until 10s. Gate
resolution was significantly lower in shorter gate. However, the possibly short measurement gate such ascorresponding to the measured signal period is important to reflect the phase noise condition of thefrequency source using time domain method intuitively.
Phase coincidence detection technology plays a key role in the measurement of periodic signals
such as frequency with high resolution, which can detect the same information about their phases
between two detected signals with identical or different nominal frequencies. It is always difficult toreach "absolute" coincidence in the implementation of phase coincidence. Thus there becomes thethreshold of phase coincidence detection sensitivity, which is the value representing the phasecoincidence when the signal phase difference is less than it. In addition, there also exists the stability ofthe threshold.
Measuring and adjusting the phase difference between standard frequency signals can make it
fixed at the threshold of phase coincidence detection circuit sensitivity. Technologically speaking, thecoincidence detection sensitivity can not be particularly high, which is often fixed in the order of ns or
hundreds of ps. If there is no effect of noise, it can still keep positive continuous coincidence
information. However, when the phase difference of the two signals is adjusted to the verge of
coincidence detection sensitivity, the output can also be detected if there is no noise. But if there isnoise, the phase variation will be between the inner and outer of the verge, thus the information of phasecoincidence will not always exist. So we can judge the phase instability of signals accurately from thecontinuity and discontinuity of the coincidence information. This is our continuous and discontinuous
condition according to coincidence information to accurately judge the signal phase instability. The
fastest response time can reach nominal period of the signal. Oscillators with low phase noise and highstability have apparent continuity of coincidence status, while the ones with relatively poor phase noiseand stability will have apparent discontinuity of coincidence and the width of the discontinuity will be
relatively large.
Thus the transient frequency stability can be identified from the unstable state of interrupted,
disability of coincidence detection circuit and the measurement result of the phase difference. The
measurement resolution depends on disability of 5ps of the coincidence detection circuit.
The formula for calculating is derived from the formula of Allen variance:(Ti 1  Ti ) 22m
i 1
Where Δ T represents the phase difference, and τ the duration of the corresponding period time.
Continuous coincidence detection based on the periodic of the signals can realize the stability
measurement. For example, 10 MHz can reach the measurement of 100 ns of the stability response time.
At the same time, when we started the stability measurement of 1 μs, 10 μs and 100 μs, we should takethe total coincidence variation in 10, 100 and 1000 periods into account. The emphasis should be put on
the analysis of the width of discontinuity coincidence point which can be converted into phase amplitude
information.

 y ( ) 

1

m




IFCS-EFTF2-PAB2-12

Phase noises of GaN-based surface acoustic wave oscillator
Rimantas Miškinis1, Emilis Urba1, Dmitrij Smirnov1, Albertas Sereika2, Romualdas Rimeika2,
Daumantas Čiplys2
1

Metrology Department, Center for Physical Sciences and Technology, Vilnius, Lithuania
2Radiophysics Department, Faculty of Physics, Vilnius University, Vilnius, Lithuania
Email: miskinis@pfi.lt

The phase noise is one of the most important characteristics of oscillators determining its application
possibilities. Gallium nitride is a material of interest with respect to electronics1. Our aim is toinvestigate the phase noise features of a GaN-based surface acoustic wave oscillator as well as to reveal
the possibilities for employing such a device as a sensor of ultraviolet radiation. We use a structure
similar to that described in the paper102. The GaN layers were grown by low-pressure metalorganic
chemical vapor deposition on (0001) sapphire substrates. A pair of Al interdigital transducers was
deposited on the GaN layer surface. Several samples with layer thicknesses in the range from 1.4 to 2.4
m and transducer period of 24 m were used. The corresponding resonant transducer frequencies
ranged from 200 to 310 MHz. The distance between the transducers was 11 mm. This two-port SAW
delay line was connected to a feedback loop of a wide-band ampliﬁer. The output signal of the SAW
oscillator was fed to a frequency counter.
The time base of the SR 620 frequency counter was disciplined to the 10 MHz signal of the Lithuaniannational time and frequency standard HP5071A. With the measurement results being saved every
second, we obtained the two series for each structure – one in the darkness and another with UV
illumination. We used a 15 W lamp of the BLB type with the maximum at about 365 nm as a source of
UV radiation. Both series were longer than 48
hours. Further, we discuss the results obtainedwith one of the structures. Average frequency
generated in the darkness was 238.38 MHz, whilethat in illumination 222.64 MHz. Fig. 1 shows thepower spectrum density Sy(f) of the relative
frequency deviation of the output signal for bothwith UV
series calculated following the instructions of thestandard103. It is seen that the signal obtained with
UV illumination features generally higher noisedarklevel, with some irregularly spaced peaks on the
PSD graph. Noise level shall be taken into
account while designing frequency shift-based Fig. 27: Power spectrum density (PSD) of the
UV sensors to make sure that the frequency shift output signal obtained with and without UV
obtained has not been overwhelmed by the phase illuminationnoise.

102

D. Ciplys et al, “Visible–blind photoresponse of GaN-based surface acoustic wave oscillator”, Appl. Phys. Lett., vol. 80,
No. 11, p. 2020- 2022, 2002.
103

IEEE Standard Definitions of Physical Quantities for Fundamental Frequency and Time Metrology – Random
instabilities, IEEE Standard 1139 (July 1999).

IFCS-EFTF2-PAB2-13

Balanced SAW Oscillator in Composite Configuration with
Colpitts and Cross-Coupled Pair
Yao Huang Kao and I-Jhih Wu
Department of Communication Engineering, Chung Hua University, Hsinchu Taiwan
Email: yhkao@chu.edu.tw
The oscillators with high quality-factor resonators in balanced configurations have received muchattention. 104 These have the advantages of reduced noise, good power supply rejection ratio, and direct
matching to the inputs of preceded stages. Recently two balanced SAW oscillators with two parallel
Colpitts and with cross-coupled pair have been presented. 105 As compared, the former has better phasenoise but suffers from the long transition due to the lack of phase inversion in initial growing. On thecontrary, the latter has the opposite results. In this study a modified Colpitts architecture embedded withcross-coupled pair is investigated. The circuit is implemented under TSMC 0.18um CMOS process. The
inherent feature of phase inversion needed for the parallel Colpitts can be easily provided by the crosscoupled pair. With the enhanced pair, the waveform transition speed is raised and thus, the start up andphase noise is improved. Actually, the cross-coupled pair also acts as latching in digital circuit. Here, thedesign of the pair size is carefully traded between latching and phase noise as shown in Fig. 1. The
performances in cross coupled oscillators w/o Colpitts are summarized in the table I. The composite one
m1 better performance in terms of figure of merit (FOM).
indeed behavesnoisefreq= 1.000MHz
pnmx=-154.9 dBc
0

Table I Performance List
pnmx, dBc

-50

-100

m1
-150

-200
1

1E1

1E2

1E3

1E4

1E5

1E6

1E7

noisefreq, Hz

(a)
0

m4
noisefreq=1.000MHz
pnmx=-164.051

pnmx, dBc

-50

-100

m4

-150

1

1E1

1E2

1E3

1E4

1E5

1E6

5E6

noisefreq, Hz(b)Fig. 28: Calculated Phase Noises in (a) crosscoupled CMOS oscillator and (b) composite
oscillator with Colpitts and cross coupled pair.

2

Cross-Coupled
Pair

CMOS Process

0.18um

0.18umPower Supply(V)

1.6(V)

1.6(V)

3.05(mA)

4.45 (mA)

Total Power Dissipation (mW)

4.88(mW)

7.12 (mW)

Oscillator Frequency(MHz)622.642(MHz)622.7 MHz

Phase Noise(dBc/Hz@1MHz)- 153.59 dBc/Hz- 164 dBc/Hz

Output Power(dBm)- 4.44(dBm)

4.47(dBm)   2

1
FOM  10 log  L   P   

0.545*0.510 (mm2) 0.68*0.585 (mm2)202

M. Aissi, E. Tournier, M.A. Dubois, C. Billard, H. Ziad, and R. Plana, IEEE RFIC Sym., 2006 , 24– 28.

Y. H. Kao and I. J. Wu, IEEE NEWCAS, 2011, p. 995-998.

Cross-Coupled
Pair & Colpitts

Total Current(mA)

Chip size(mm2)

-200

104

Oscillator

211

IFCS-EFTF2-PAB2-14

Integrating performance and production oriented design ofsatellite oscillators
Eskelinen Harri1, Eskelinen Pekka2,
1

Lappeenranta University of Technology / School of Mechanical Engineering / Finland
2
Aalto University / School of Electrical Engineering, Helsinki / Finland
Email: harri.eskelinen@lut.fi

This paper continues the research106, in which the manufacturability analysis was carried out for of an
oscillator made for the 5 GHz satellite and radar bands. The electronic circuit uses two cascaded bipolar
microwave transistors in a emitter feedback amplifier configuration which is combined with acylindrical dielectric resonator. Three miniature coupling loops are included to it, one for amplifier
input, one for amplifier output via a Wilkinson power divider and another for the optional tuning
varactor diode.
We have set two research questions: Firstly, how much is it possible to increase the Q-value of theresonator by improving the manufacturing quality of its milled geometries? Secondly, is it possible todescribe the required manufacturing accuracy with the Q-value added to the PDM (Product DataManagement) data set? The scope of this paper focuses on the multidisciplinary aspects of integrated
performance and productive oriented design of satellite oscillators. For the first time the quality
characteristic (Q-value) could be utilized directly in oscillator’s mechanical PDM data to guide
production.
Experimental evaluations of the effects of dimensional uncertainties were analyzed by constructing threeresonators with different coupling loops. EdgeCAM simulations were used to evaluate the required
PDM data for guiding the milling tools. Laboratory tests were conducted to measure the achievablesurface quality and dimensional and geometric tolerances of the milled cavities.
A scalar network analyzer system was utilized and resonator center frequency, insertion loss, and quality
factor were measured with different vertical and horizontal disc positions. The wide-band spectral
response of each resonator was established. Based on the results the ceramic resonator disc alignment or
its position in the cavity was not critical compared to the circular symmetry requirement of the cavity.
When analyzing the effects of non-circular cavity cross section, it was noticed that e.g. 0.1 mm
deflection, which covers 90 degrees of the circumference of the cavity, causes the center frequency torise to 5.1206 GHz, meanwhile the insertion loss was 10.60 dB and the Q-value dropped to 8533. These
kinds of tests were repeated to collect and construct the corresponding PDM data set, which illustrates
the relationships between the values of circularity and dimensional inaccuracy of cavities and thecorresponding changes of the Q-values and the center frequencies.

106

Eskelinen H., Montonen M., Performance-Integrated DFMA Analysis of a Satellite Oscillator, Advanced approaches toanalytical and systematic DFMA analysis, Edited by Harri Eskelinen, Acta Universitatis Lappeenrantaensis 509, ISBN 978952-265-366-6, Finland, 2012.

IFCS-EFTF2-PAB2-15

Redundant Frequency Source with Seamless Switchover
Shi Shaohua1, Li Xiaohui2, Tang Sheng3
1

National Time Service Center, Chinese Academy of Sciences, Xi`an, Shaanxi, China
2
Key Lab. Of Time & Frequency Primary Standards, CAS, Xi`an, Shaanxi, China
3
Northwest University, Xi`an, Shaanxi, China
Email: ssh@ntsc.ac.cn

This paper describes a redundant frequency source system with seamless switchover that produces astable and continuous output frequency signal. This system has primary and backup frequency produce
links to generate the reference frequency. It has the ability to monitor the integrity of frequency produce
links and switchover seamlessly between the primary and the backup links. By use intermediateoscillator of the measurement system as a third party criterion, the autonomous monitor integrity of
frequency produce links was achieved without external reference signal. The excellent short-term
stability characteristics of intermediate oscillator improves the accuracy and real-time for the monitoringof sudden failure and the degradation of performance. Seamless switchover was defined as themaintenance of both output phase and frequency continuity while and after the switcher from theprimary to the backup links. It was initiated when system detects a degradation of the integrity ofprimary links. The experiment result has been presented showing that there were no detectable change inphase and frequency after the switchover, and the jump of frequency was less than 2e-13, the change ofphase less than 100ps107.

Fig. 1 Frequency change during and after switchover107

Supported by National Natural Science Foundation of China

Fig. 2 Phase change during and after switchover

IFCS-EFTF2-PAB2-16

Programmable Delay Controller Allowing Frequency Synthesis
and Arbitrary Binary Waveform Generation
Marek Peca, Michael Vacek, Vojtěch MichálekVýzkumný a zkušební letecký ústav, a. s., Beranových 130, Praha – Letňany, Czech RepublicČeské vysoké učení technické v Praze, Břehová 7, 115 19 Praha 1, Czech Republic
Email: peca@vzlu.cz
Design of a programmable delay controller (PDC) within an ordinary space-compatible fieldprogrammable gate array (FPGA) fabric is presented. Although PDC is a common digital block
nowadays108,109,110, the possibility to use it for low-jitter arbitrary frequency generation constrained only
by minimum edge-to-edge time still seems to be uncovered. The PDC being presented may be able toreplace current building blocks such as direct digital synthesizer (DDS), phase-locked loop (PLL) or
various modulators; all within purely digital circuit (i.e., FPGA). Typical PDC based on a digital
circuitry consists of fixed-length delay elements (transmission lines, gates) composed into signal path byelectronic switches (multiplexers).
The novel idea of the developed PDC is seamless line delay switching at sampling frequency fs close to
the generated output frequency fo unleashing the possibility of arbitrary binary waveform (frequency)
generation constrained only by fo ≤ fs (~100MHz). Glitch-free operation with no unintentional edges is
employed for proper PDC control signal switching.
The overall output signal (fo) jitter is composed solely of the jitter of input signal and propagation jitterof the delay elements. For the selected delay line configuration, jitter (random component), non-linearity
and resolution are presented. The overall signal path delay is continuously measured and calibratedusing time-to-digit converter111 (TDC) and/or phase meter circuits, both synthesized within the same
FPGA fabric.
Preliminary single shot jitter measured
for various signal path delays, using
pulse generator being synchronouswith TDC system/sampling clock, isabout σ=10ps (Fig. 1) for the given
space-compatible FPGA fabric.
Fig. 29: PDC single shot jitter.

108

D. C. Auth Z. L. M. Li, J.and Zheng and S. Wu, “Dynamic range accurate digitally programmable delay line with
250-ps resolution,” in 8th International Conference on Signal Processing, 2006.
109

A. de Castro and E. Todorovich, “High resolution fpga dpwm based on variable clock phase shifting,” IEEE
Transactions on Power Electronics, vol. 25, pp. 1115–1119, 2010.
110

NB6L295: Dual Channel Programmable Delay Line with LVPECL Output, ON Semiconductor. [Online]. Available:
http://www.onsemi.com.
111

M. Peca, M. Vacek, and V. Michalek, “Time-to-digit converter based on radiationtolerant fpga,” in 26th European
Frequency and Time Forum, 2012, pp. 286–289.

IFCS-EFTF2-PAB2-17

An Efficient Room Temperature Only (RTO) Trimming Solution for
an Accurate Self-Compensated Oscillator (SCO)
A. Elkholy, A. Ahmed, M. Shadoufa, M. Sakr, A. El-Sayed, M. Yousef, A. Helmy, M. Essam, N.
Sinoussi
Timing Products Division, Si-Ware Systems, Cairo, Egypt
Email: nabil.sinoussi@si-ware.com
Df/f K = 0
Driven by the continuous need for integration and cost
reduction, research is eager to find a proper CMOS
F
Temp
T
compatible replacement for quartz crystal oscillators
SCO
Frequency toD
TempF(XOs). In a previous work112, a self-compensated Temperature
K Detection
Digital Converter
Modulation
Module(FDC)
ModuleCMOS LC oscillator (SCO) based on LC tankPStemperature null (TNULL) phenomenon wasK
introduced. The SCO forces the LC tank to operate at its
Excitation Signal
Trimming Algorithm
Excitation Signal
specific TNULL phase (φNULL) where the oscillator
exhibits a frequency deviation of few tens of ppms Fig. 30: Block diagram of RTO infrastructure.
across a given temperature range. However, process
variations affect the value of φNULL. Thus, trimming isrequired to compensate for these variations. Since it candegrade the overall cost and accuracy of the solution,
trimming is one of the major challenges in having ahighly accurate and fully-integrated LC-based reference
clock generator.
T

ref

o

To

osc

osc

T

T

This work presents a new on-chip room temperature
only (RTO) trimming solution for a highly accurate
SCO with minimum testing overhead. The main
objective of the trimming procedure is to search for the
optimum phase setting (PSopt) which adjusts oscillator
Fig. 31: The frequency deviation acrossphase to φNULL. Fig. 1 shows the block diagram of thetemperature of 50 parts trimmed using the RTO
RTO trimming infrastructure. It utilizes on-chip heaters
to produce 25MHz CMOS output.
to modulate the oscillator thermally. The oscillator
output becomes a frequency modulated (FM) signal whose modulation depth depends on the frequency
sensitivity to temperature (KT). Using a frequency-to-digital converter (FDC) referred to an externalreference frequency (Fref), the oscillator FM signal is demodulated; hence, KT is extracted. An intelligent
trimming algorithm is used to search for PSopt by adjusting the SCO KT around room temperature to beapproximately zero; hence, obtain the optimum SCO temperature dependence.
The SCO is implemented with the fully-integrated RTO trimming infrastructure on a standard CMOS
0.18μm technology. The RTO is utilized to trim 50 parts to produce 25MHz CMOS output. The parts aretrimmed in parallel such that the average trimming time consumed per part is less than 1s. Fig. 31 shows themeasured frequency deviation versus temperature of the 50 parts. The SCO achieves ±50ppm frequency
stability across temperature from -20°C to 70°C.

112

A. Ahmed et al., "A Highly Stable CMOS Self-Compensated Oscillator (SCO) Based on an LC Tank Temperature Null
Concept," Proc. IEEE FCS-EFTF, May 2011, pp. 443 – 447.

IFCS-EFTF2-PAB2-18

GRAIL USOs; Another In-Flight Quartz Radiation Experiment
Weaver Gregory1, Asmar Sami, Oudrhiri Kamal2
1

Space Department, Johns Hopkins University Applied Physics Laboratory, Laurel, MD/USA
2
Radio Science Systems Group, NASA Jet Propulsion Laboratory, Pasadena, CA/USA
Email: gregory.weaver@jhuapl.edu

The Gravity Recovery and Interior Laboratory (GRAIL) mission successfully ended on
Dec. 17th, 2012 after an extended science phase of over 280 days mapping the gravitation field gradientof the Moon with a precision of better than 50 E-6 g’s over the entire lunar surface. The mission was
performed by two tandem flying spacecraft named Ebb and Flow, both of which carried a JPL
Microwave Dual One-way Ranging (DOWR) instrument that together formed a highly precise relative
measure of the distance between the two spacecraft as they orbited the Moon.
The precision of the radio link maintained by the DOWR instruments was derived from the highfrequency stability of the JHU/APL ultra-stable oscillators USO on-board each spacecraft. D. G. Enzer,
et. al. describe the rare ability to extract the individual frequency stability of both in-flight GRAIL USOs
without consideration of atmospheric propagation or the use of ground-clock comparison.113 The
opportunity to observe the USOs frequency throughout the GRAIL mission provides a record of not
only the intrinsic performance of the oscillators,
but their behavior during exposure to spaceconditions.
Reaction of quartz resonators (such as used in the
GRAIL USOs) to ionizing radiation is wellknown. In 2003, an analysis of the Milstar FLT-1
on-board oscillator’s frequency behavior duringexposure to solar flares, described as a spaceexperiment, was performed using space-weather
data accumulated by the GOES.114 In our paper,
we will follow with another ‘space experiment’
analysis of the frequency effect of the March 7 th,2012 X5.4 level solar flare on the GRAIL USOs, Fig. 32: Proton flux data collected from theOperational
Environmental
which were in lunar orbit at that time. Fig. 1 Geosynchronous
Satellite GOES 13 during the ingress of ionizingthshows the intensity of the March 7 proton flux
radiation from the X5.4 solar flare of Mar 7th, 2012.
detected by GOES 13. We will discuss the impactof this radiation exposure, and the asymmetricbehavior of two space-oscillators coincidentally perturbed by the same space-weather event.

113

D. G. Enzer, R. T. Wang, K. Oudrhiri, W. M. Klipstein, “In situ measurements of USO performance in space

using the twin GRAIL spacecraft”, 2012 IEEE IFCS Proc., p. 533-537
114

S. D. LaLumondiere, S. C. Moss, J. C. Camparo, "A "space experiment" examining the response of a geosynchronous
quartz crystal oscillator to various levels of solar activity," IEEE Trans. UFFC, vol.50, no.3, pp.210-213, March 2003

IFCS-EFTF2-PAB2-19

Long-Term Stability of a MEMS Disk Oscillator
Tristan O. Rocheleau, Thura Lin Naing, and Clark T.-C. Nguyen
University of California at Berkeley, Berkeley, CA, USA
Email: Tristan@eecs.berkeley.edu
A low phase noise oscillator referenced to a wine-glass
disk MEMS resonator, hermetically vacuum packaged,
and measured in a double-oven system, cf. Fig.1, hasprovided a first long-term measurement of a MEMS
oscillator over 6 months. After an initial burn-in period,
the frequency can be seen to stabilize to within the shortterm measurement variation of ±300 ppb over a period ofmonths, a significant improvement from previous studies
on other MEMS resonator types 115,2, where frequency Fig.1: The 61-MHz wineglass disk
fluctuations were ±3.1 ppm1 and ±1.2 ppm2 over similar oscillator. The circuit on left is hermeticallytime scales. Including burn-in, the total observed aging of sealed in the package and double oven on
9 ppm is now on par with many consumer quartz the
right
for
temperature-stablemeasurements.
oscillators3 designed for timing applications.
Wine-glass disk oscillators are known to exhibit
exceptional short-term stability, having met thechallenging GSM phase noise spec. some time ago2, but
long-term stability has until now been unpublished. To
remedy this, Fig.1 presents the measured MEMS
oscillator, comprised of a wine-glass disk resonator bondwired to a custom transimpedance amplifier andhermetically packaged in a custom-built vacuumpackaging system capable of maintaining torr pressures.
A double-oven system maintains a constant oscillator Fig.2: Measured frequency drift andtemperature at 34°C with less than 0.001°C deviation, a temperature stability of the MEMS
oscillator. Frequency measurements were
key improvement over previous long-term studies1.
made using an Agilent 53230A frequency
Fig.2 presents measured oscillator frequency versus time counter with a 100s measurement time.
data over a half year aging period, exhibiting the same
logarithmic decay behavior typical for quartz oscillators3. The increasing frequency suggests stressrelaxation over mass loading or package leaks as the aging mechanism—no great surprise as bothbondwires and high-temp glue adhering the die to package would be expected to produce strain. Despite
this, performance is good, on par even with low-cost quartz oscillators. This is not unexpected for suchwine-glass devices, for which supports attached to quasi-nodal points on the resonant disk structure
greatly isolate the disk from the substrate and its associated stress changes.

115

B. Kim et al., “Frequency Stability of Wafer-Scale…”, Sensors and Actuators A, vol. 136, p. 125-131, 2007

2

R. Tabrizian et al., “A 27 MHz Temperature Compensated MEMS Oscillator…”, Proc. MEMS 2012, p. 23-26

3

J. R. Vig and T. R. Meeker, “The Aging of Bulk Acoustic…”, Proc. IFCS 1991, p. 77-101

4

Y.-W. Lin et al., “Series-Resonant VHF…”, JSSC, Vol. 39, No. 12, p. 2477-2491, 2004

IFCS-EFTF2-PAB2-20

All-Digital Frequency Synthesis based on Single-Bit Nyquist-Rate
Sinewave Quantization with IID Random Dithering
Paul P. Sotiriadis1, Natalia Miliou1,
1

Department of ECE, National Technical University of Athens, Greece
Email: miliou@ieee.org

The interest in all-digital frequency synthesis (FS) has been intensified in the R.F.I.C. industry over the past
few years due to the challenge in the design and the extra cost of fabrication of R.F. analog and mixed-signal
I.C. versus standard digital ones in modern nano-scale I.C. technologies. Efforts towards all-digital FS can betraced at least thirty years back116. This paper proposes single-bit dithered Nyquist-rate quantization of asinewave as a method for all-digital FS.
The concept is illustrated in Fig. 1 where a random sequence uk  (dither) is subtracted from the sinewave
and the result is quantized producing signal x k  sgn  cos  k   uk  . Here Ts  1 / f s is the sampling
period. Since cos  k  can be generated with very high precision using a LUT, the single-bit quantization isby far the dominant source of spurs and noise. In this sense Fig. 1 is a classical DDS with high resolution
LUT, amplitude dithering and a 1-BIT DAC (i.e. an MSB truncator). We consider independent andidentically distributed dithering sequences with continuous Cumulative Distribution Function (CDF)
G : [1,1]  [0,1] which we express as a series of Chebyshev polynomials of the first kind, i.e.,
1 1 G  u     j 0  jT j  u  . Using the coefficients  j we derive the power spectral density (PSD) of the
2 2
output x  t  to be:  2  


k
j 
1  2 2
2
S x  f   sinc2  f TS     j    f    Ts  1  a0   a j   a0    f  
Ts 2 Ts 
2 j 1  j 1 4 k  where the first term (sum) in the brackets is the desirable frequency component at  /  2 Ts  along with all
harmonics present (modulo f s ), the second term is the continuous noise floor and the third one is the DC
component of the output. We define the dynamic range (DR) as the ratio of the power of the frequency
component at  /  2 Ts  over the noise’s PSD at the same frequency and derive:DR  10log10  r  a 12 qr / 2  2a02 

 a   10log  fs   3.01 . The paper also presents necessary and


j 1

2
j

10

sufficient conditions for spurs-free output, like that in Fig. 2 (without the sinc2  f TS  factor) and CDFs

cos(Ωk )

xk

1

+

ZOH
-1

-

x t

Ts

uk

PSD (dB)0-10

fs = 1 GHz-20

RBW = 3125 Hz-30

Nav = 10

-40
-50
-60

0

Fig. 33: Dithered single-bit sinewave
quantization
116

DR = 87 dB

0.2

0.4 f / fs

0.6

0.8

Fig. 2: Normalized PSD ( f S  1 GHz )resulting in a variety of DR values and spectra.

V.S. Reinhardt, “Direct digital synthesizers”, Technical Report, Hughes Aircraft Co, L.A., CA, Dec. 1985.

1

IFCS-EFTF Group 3 poster session 1
Forum Hall
Monday & Tuesday, July 22-23, 2013, 01:00 pm - 02:00 pm and 3:30 pm - 4:30 pm
Chair:

Elizabeth Donley
NISTIFCS-EFTF3-PAB3-1

Comparative Performance of Compact Schemes of Atomic BeamLongitudinal Deceleration Designed for Space-Based Frequency
Standards
Vadim Zholnerov1, AntonVershovskii2, Yuri Rozhdestvenskiy1
1

2

Russian Institute of Radionavigation and Time, St.-Petersburg, Russia
Ioffe Phys.-Tech. Institute of Russian Academy of Science, St.-Petersburg, Russia
Email: zholnerov@mail.ru

Space-based frequency standards are probably the most important parts of any global navigation system.
Optical frequency standards demonstrating the unique stability are extremely promising for space
applications. Nevertheless, the stringent requirements to these applications force us to look for simpler
technical solutions; among these, the radiofrequency standards using cold atom beams seem to have thegreatest potential, and one of the solutions involves the use of CPT-Ramzey resonance opticaldetection117.
Since the sensitivity of any scheme of registration of radio-optical resonance in an atomic beam islimited by the longitudinal velocity of the atoms, the velocity of the order of 1 m/s and registration area
length of at least 0.5 m are required for obtaining stability of 10 -15. The combination of theserequirements, in turn, limits the allowable transverse velocity of the atoms in the beam.
The optical preparation of the atomic beam characterized by the longitudinal velocity of 1 m/s and adivergence of 0.05 rad is a difficult task due to the limitations of the existing slowing schemes. There are
two types of these schemes – so-called “laser chirping”, and “Zeeman slowing”; the latter allows acontinuous beam of cold atoms to be obtained, which is considered an advantage. In practice, however,none of these schemes in their classic versions provide a longitudinal deceleration of atoms below
10 ÷ 20 m/s because of the significant time needed for slowing of atoms from the initial thermal
distribution to a narrow velocity peak.
Therefore it was proposed1 to significantly reduce the upper limit v0 of the initial velocities of the atoms
that interact with the laser radiation. In this case, the time of longitudinal deceleration dramaticallydecreases, which gives hope for obtaining the number of atoms with velocities ≤ 1 m/s sufficient forregistration. The operating mode of such a slower is pulsed; some loss of intensity of the atomic beamoccurs in this scenario, since only the slowest part of the thermal beam interacts with the cooling light.
Thus, at a speed v0 corresponding to one-half of the average thermal velocity, about 2% of a thermal
beam are effectively used; this is compensated by shorter time (and hence the shorter slowdown lengthand less required power), and smaller transverse dimensions of the beam of atoms in the registration
area..
In the present report, we numerically simulate the process of longitudinal cooling of the atomic beam intwo slowing schemes, varying the initial velocity range and comparing the characteristics of the laser
chirping and Zeeman slowing methods. We also examine the effectiveness of modifications of thesemethods implying use of a multimode cooling light. Estimates of the number of cold atoms required toobtain a stable CPT-Ramzey resonance signal are presented.

117

V. S. Zholnerov, A. K. Vershovskiy, Yu. V. Rozhdestvenskiy, “Project of a Satellite Slow Beam Atomic Clock with CPTRamsey Registration”, Proc. EFTF-2012, Gothenburg, Sweden, p.320-322, 2012.

IFCS-EFTF3-PAB3-2

Medium- to Long-Term Frequency Stability of High-Performance
CW Double-Resonance Rb standard
Thejesh Bandi1, Christoph Affolderbach1, Camillo Stefanucci2, Francesco Merli2,3,
Anja K. Skrivervik2, Gaetano Mileti1
1

Laboratory of Time & Frequency (LTF), University of Neuchâtel, Neuchâtel, Switzerland
2
Laboratory of Electromagnetics and Acoustics (LEMA), EPFL, Lausanne, Switzerland
3
Present address: RF Division, HUBER+SUHNER AG, Herisau, Switzerland
Email: thejesh.bandi@unine.ch

We have developed a compact high-performance laser-pumped Rb cell frequency standard suitable inparticular as onboard GNSS oscillator118. It has a volume (physics package and laser head) V < 3 dm3, mass
< 2 kg and power consumption < 18 W. The clock exploits an enlarged magnetron-type microwave cavity119
having TE011-like mode that can hold the vapor cell of 25 mm diameter. A preliminary short-term frequency
instability exhibiting <1.4x10-13 -1/2 was reported120.
In this communication we present detailed short-term
noise budget analysis. A systematic metrologicalcharacterization of perturbing physical effects
influencing the medium- to long-term clock frequency
instability, such as the 2nd-order Zeeman shift, lightshifts, microwave power shift, cavity pulling, spinexchange shift, and the temperature coefficient shifts
will be presented.
We measure intensity light-shift coefficient () of 2.85(2)x10-12 mm2/W. At this condition of reduced ,
we study the microwave power shift, and observe that Fig. 34: Microwave power shift dependence on
the magnitude of microwave PS depends on the the pump light intensity. The laser frequency isinterrogating laser light intensity as shown in Fig. 1. stabilized close to the center of the optical
For instance, at an input laser intensity of 8 W/mm2, transition in the clock cell.
one can nullify the effect of microwave power shift.
We also present the frequency light-shift coefficient () and show its dependence on the input laser intensity.
These studies are of relevance for improving the medium- to long-term frequency stability of portable Rb
cell standards, by compensating for the light-shift coefficients ( and ), microwave power shift, cavity
pulling, second-order Zeeman shift and vapor cell temperature coefficients.
Acknowledgements: This work was supported by the SNSF (grant no. 140712) and the ESA. We thank C. E.
Calosso (INRIM, Italy) for the microwave synthesizer (LO). We thank F. Gruet, M. Pellaton, P. Scherler and
M. Dürrenberger (all LTF) for technical support.

T. Bandi et al., “Laser-pumped high-performance compact gas-cell Rb standard with < 3x10-13 -1/2 stability”, Proc. ofEuropean Frequency and Time Forum (EFTF), Gothenburg, Sweden, April 24-26, 2012, pp. 494-496.
118

119

C. Stefanucci, T. Bandi, F. Merli, M. Pellaton, C. Affolderbach, G. Mileti, A. K. Skrivervik, “Compact microwave cavity
for high performance rubidium frequency standards”, Rev. Sci. Instrum., vol. 83, 104706, 2012.
120

T. Bandi et al., “Double-resonance in alkali vapor cells for high performance and miniature atomic clocks”, Proc. of IEEE
International Frequency Control Symposium, Baltimore, USA, May 21-25, 2012, pp. 686-691.

IFCS-EFTF3-PAB3-3

Dynamic Stark Effect in the Rubidium End Resonance with Laser Pumping
A.A.Baranov, S.V. Ermak, V.V. Semenov
Department of Quantum electronics, Saint-Petersburg State Polytechnic University,
Saint-Petersburg, Russia
Email: lexusbar@gmail.com
In a work121 a novel end resonancetechnique based on the optical orientation of theworking atoms was suggested. This techniqueimplementation
decreasespin-exchange
broadening of the resonance line in comparison
to the magnetic-independent 0-0 resonance.
However, light and orientation frequency shiftinaccuracies weren’t taken into account, whereas
they inevitably lead to resonance frequency
instability122. In this work we present analyticaland experimental studies on the light shiftcomponent in the case of 1 degree uncertainty of
the angle between magnetic field and optical axis Fig. 35: Light shift curves for m = 0 → 0 (a) andf
directions. The results were carried out for Rb87 mf = 1 → 2 (b) transitions with laser tuned to Rb87
atoms pumped by a circular polarized laser beam D1 line, F=1 level.
of 100 μW/cm2 intensity and 100 MHz
linewidth. Table 1 contains the calculated results of the research. Light shift curves for mf = 0 → 0 and
mf = 1 → 2 resonances in relation to the short-wave component of the D1 line are sown on Figure 1.
Experimental data has a good matching with the analytical estimates.
Table 1.
D1Hyperfine level
Light polarization
Light shift curve
toughness (Hz / MHz)
Orientation inaccuracy(1° C-field variation)

D2

F=1

F=2

F=1

F=2

σ+

σ-

σ+

σ-

σ+

σ-

σ+

σ-

3

8

5

1

5

-10

10

3

4·10-13

3·10-13

4·10-12

3·10-12

3·10-13

7·10-13

3·10-12

4·10-13

121

Y-Y Yau, A.B.Post, N.N.Kuzma, A.M.Braun, M.V.Romalis, W.Happer .- Intens, Narrow Atomic-Clock Resonances,
Physical Review Letters, v.92, №11, P.110801-110801-4, 2004.
122

A.A. Baranov, S.V. Ermak, V.V. Semenov Orientation Frequency Shift of 0-0 Hyperfine Resonance in Rb87 Vapor with
Selective Optical Pumping.- Optics and Spectroscopy, 2013, Vol. 114, No. 3, pp. 337–339. © Pleiades Publishing, Ltd.,2013.

IFCS-EFTF3-PAB3-4

2nd-Harmonic Signals in Vapor-Cell Clocks as a Measure of Error-Signal Quality

James Camparo and Gilda Fathi
james.c.camparo@aero.org
Physical Sciences Laboratories
The Aerospace Corporation, 2310 E. El Segundo Blvd., El Segundo, CA, 90245, USA
In the standard frequency-feedback loop of atomic clocks, a field’s frequency is modulated at fm, and theatomic dynamics are detected and demodulated at the fundamental frequency (i.e., the 1st harmonic).
This 1st-harmonic signal, S1, is used to generate a correction for the clock’s voltage-controlled crystal
oscillator (VCXO), locking its output frequency to the atomic system. An intuitive understanding of thisprocess is typically obtained by viewing the atomic dynamics in terms of the quantum system’s static
response to a resonant field: the 1st harmonic atomic dynamics are taken as proportional to the 1stderivative of the static resonance lineshape, the 2nd harmonic dynamics proportional to the 2nd
derivative, etc. This quasi-static approximation suggests that the 2nd harmonic signal, S2, can be used toassess the atomic signal’s quality for frequency stabilization purposes. Specifically, since the 2nd
derivative of the lineshape is proportional to the slope of the 1st derivative, the quasi-static
approximation suggests that one can take S2 as a measure of the atoms’ frequency-discrimination
capability: S2 ~ dS1/d, where  is the frequency detuning of the VCXO’s (multiplied) output frequency
from the atomic resonance.
The problem with this logic, however, is that in order to obtain large signal-to-noise ratios and narrowatomic linewidths it is typical for atomic clocks to operate under conditions where f m ~  ~ , with and  the Rabi frequency and relaxation rate, respectively. This regime of operation is neither quasistatic (large ), adiabatic (large ), nor sudden (large fm). Consequently, none of the standard
approximations of quantum dynamics legitimately apply, notably the quasi-static approximation.
In order to develop a better intuitive understanding of atomic dynamics in the regime of clock operation,and in particular the nature of the atoms’ 2nd harmonic response to a frequency modulated field, we havebegun a series of experiments investigating 2nd harmonic signals as they appear in rubidium atomic
clocks. In this presentation we will first discuss our experimental 2nd harmonic testbed, which employs
a diode laser for Rb87 optical pumping instead of an rf-discharge lamp to allow better experimental
control over the light shift. Following this, we will discuss our initial results comparing S2 with dS1/d
for different modulation frequencies, and how well these results agree with a Quasi-Static
Approximation (QSA) theory and a Small Modulation-Signal (SMS) theory. (Both of these theories
yield closed-form expressions for S2 and dS1/d, as opposed to non-intuitive tables of numbers.) In
brief, we find that the SMS theory is much better at predicting the relationship between S2 and dS1/d
than the QSA theory. This has relevance for atomic clocks, because at present engineers use empirical
relationships between S2 and dS1/d to set the optimum microwave power-level for their clock’s
operation (i.e., the optimum power-level for dS1/d). Should the SMS theory’s validity continue to be
substantiated, it will give engineers a better understanding of the basic atomic physics that underpins
their empirical relationships.

IFCS-EFTF3-PAB3-5

Higher-order Sideband Excitation
for Pulsed CPT Atomic Clocks
Shigeyoshi Goka, Yuichiro Yano
Graduate School of Science and Engineering, Tokyo Metropolitan University,
Hachioji, Tokyo 1920397, Japan
Email: goka@tmu.ac.jp
A higher-order sideband excitation method combined with a pulse excitation is proposed to reduce
power consumption of coherent population trapping (CPT) atomic clocks. Since the higher-order
sideband excitation enables reduction of RF frequency, our method can significantly reduce switching
power loss of a RF generator and its peripheral circuits. In the previous work[1], we reported the CPTRamsey resonances using a liquid crystal modulator for low power operation, therefore, our method canbe applied to chip-scale atomic clocks (CSACs).
A 895 nm vertical-cavity surface-emitting laser (VCSEL) was used to excite Cs at the D1 line. The Cs
gas cell had a optical length of 20 mm and contained 133Cs atoms and 4.0 kPa of Ne buffer gas at acontrolled temperature of 42 ºC. The linearly polarized (lin || lin) laser beam was intensity-modulated byan acousto-optical modulator (AOM) to excite a CPT-Ramsey resonance. The pulsed laser light fieldwith the 1.0 kHz switching frequency was generated by the AOM. The modulation RF frequency fRF
was set as fRF = fhfs / 2n. Here, fhfs is the hyperfine-splitting frequency and n is the sideband order. Since
switching power loss of RF is proportional to its frequency, lower fRF can reduce power loss of a RF
generator and its peripheral circuits. The measured CPT characteristics excited by the continuous andpulse method are shown in Table 1.
The experimental results show that the 3rd-order sideband excitation can lead to narrow fringe widthand high contrast compared with the conventional continuous excitation (n = 1). The relative figure of
merit was 2.3 and the relative light shift was less than one-third that with the conventional excitation.
These results indicate that our method can reduce RF switching power loss and improve frequency
stability.
Table 1 Measurement values with higher-order sideband pairs under continuous and pulse excitation.
Excitation
MethodContinuous

Pulse

Sideband
Order

fRF
[GHz]

Contrast[%]

FWHM

Q value(fRF / FWHM)

n=1

4.596 325

3.3

2.32 kHz

1.98×1066

Relative Light
Shift[10-12/(μW/cm2)]
18.6

Figure of Merit(Q value ×Contrast)

Relative
Figure ofMerit

6.5×106

1.0

115

1.5×106

0.23

n=2

2.298 162

0.7

1.09 kHz

2.11×10n=31.532 1080.8

700 Hz2.19×106118

1.8×106

0.27

n=1

4.596 325

5.3

406 Hz1.13×107

0.602

6.0×1079.2

n=2

2.298 162

1.8

216 Hz1.06×107

3.82

1.9×1072.9

n=3

1.532 108

1.4

142 Hz1.08×107

5.86

1.5×107

2.3[1] "Pulse Excitation Method of Coherent-Population-Trapping Suitable For Chip-Scale Atomic Clock," Yuichiro Yano,
Shigeyoshi Goka, Jpn. J. Appl. Phys. 51 (122401) 2012

IFCS-EFTF3-PAB3-6

The NPL Primary Frequency Standard System
K. Szymaniec, S. N. Lea, K. Liu*, P. B. Whibberley
National Physical Laboratory, Teddington, UK
National Institute of Metrology, Beijing, China*

Email: ks1@npl.co.uk
At the National Physical Laboratory, a system of primary frequency standards (PFS) is being
developed with the aims of quasi continuous calibration of the duration of the step interval of theinternational time scales UTC and TAI, provision of stable reference and steering parameters for the
local representation of UTC maintained by NPL, and absolute frequency measurements of atomic
frequency standards being developed as secondary representations of the second.
This PFS system will consist of two caesium fountains. A microwave synthesizer based on an
optical frequency comb referenced to an ultra-stable laser is being developed to replace the existing
quartz local oscillator. One caesium fountain, NPL-CsF2, has been fully operational since 2009;
following an initial accuracy evaluation in 2010 a reduced type B uncertainty of 2.3 × 10-16 waspublished in 2011, taking into account improved evaluation of the distributed cavity phase (DCP)
shift123. A second fountain, similar to NPL-CsF2 in design and expected performance, is currently being
assembled and preliminary operation is planned for summer 2013.
The design of NPL-CsF2 is relatively simple, with a single stage magneto-optical trap (MOT) withcooling beams in the (0,0,1) configuration. The small size of the atomic cloud released from the MOT is
an advantage for cancellation of the collisional frequency shift124. An additional optical pumping stage
accumulates the atomic population in the mF = 0 clock state, resulting in a five-fold increase in thedetected atomic signal125. This also enables the fountain to be operated at a higher densities of atoms,
further reducing the uncertainty in extrapolation to zero density. The new fountain, NPL-CsF3, will
incorporate many features of NPL-CsF2. The major novelty is a new microwave cavity designed tominimize the DCP shift126.
NPL-CsF2 has been producing data almost continuously since early 2009. Unintentional breaks
occur on average less than once in 33 days. Intentional interruptions are scheduled for system and lab
maintenance. To date, 37 UTC evaluations have been reported to BIPM, covering 780 days, with typical
total uncertainty (including frequency transfer uncertainty) of 4 × 10-16. Since February 2011 a pilot
scheme has been run to enhance the generation of the UTC(NPL) time scale. The setup consists of a freerunning hydrogen maser with its frequency shifted in an external offset generator according tomeasurements made by the fountain.
Highlights of our design and details of operation will be presented, together with discussion of longterm performance and results of calibrations of UTC and of UTC(NPL).

123

R. Li, K. Gibble, K. Szymaniec, “Improved accuracy of the NPL-CsF2 primary frequency standard: evaluation of distributed
cavity phase and microwave lensing frequency shifts”, Metrologia, vol. 48, p. 283–289, 2011.
124

K. Szymaniec, W. Chalupczak, E. Tiesinga, C. J. Williams, S. Weyers, R. Wynands, “Cancellation of the collisional frequency
shift in caesium fountain clocks”, Phys. Rev. Lett, vol.98, p.153002-1, 2007.
125

K. Szymaniec, H-R. Noh, S. E. Park, A. Takamizawa, “Spin polarisation in a freely evolving sample of cold atoms”, Appl. Phys.
B, (in press).
126

K. Gibble, S. N. Lea, K. Szymaniec, “A microwave cavity designed to minimize distributed cavity phase errors in a primarycesium frequency standard”, Conference on Precision Electromagnetic Measurements (CPEM), p. 700–701, 2012.

IFCS-EFTF3-PAB3-7

Reducing the Blackbody Radiation Shift in the NIM new fountain design
Fang Fang*, Xiaoke Yan, Weiliang Chen, Kun Liu, Nianfeng Liu, Rui Suo, and Tianchu LiTime and Frequency Division, National Institute of Metrology,
Beijing, P. R. China*E-mail: fangf@nim.ac.cn
We are developing a new Cs fountain frequency standard in NIM, and shooting for the frequency
uncertainty of a few parts in 1016. The new fountain will run in a lab with the temperature fluctuation of
0.3K, and no active temperature control system will be added outside the flight tube of the fountain.
Instead, an annular glass-water heat pipe will be used as an isothermal liner surrounding the flight tube
to attenuate the temperature variations and improve temperature uniformity. The thermal conductivity ofa glass isothermal liner is about 10 times higher than that of coppers. According to the working principleof heat pipe, it also works like a low pass filter, and reduces the temperature fluctuations of the system.
The advantage of using an isothermal liner is to make the temperature of the whole interrogation region
more uniform and stable. With precision standard platinum resistance thermometers measuring thetemperatures of a few locations of the flight tube, the averaged temperature uncertainty is less than 50
mK. The frequency shift due to the blackbody radiation can be calculated according to the equation:T/300)^4[1+(T/300)^2]x. With the coefficient of =−1.572(6)E-4 and =1.3(1)E-2xi,xii, the black
body radiation shift can reach down to 8.5E-17 of this new fountain clock design.

IFCS-EFTF3-PAB3-8

Improvements of the atomic fountain clock at SIOM
Yuan-bo Du1,2, Rong Wei1, Ri-chang Dong1,2, and Yu-zhu Wang1
1

Key Lab for Quantum Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, China, 201800;
287

University of Chinese Academy of Sciences, Beijing, China, 100049

A compact Rb atomic fountain clock has been evaluated in Shanghai Institute of Optics and Fine Mechanics, Chinese
Academy of Sciences, comparing with a H-maser, the stability of the clock has been measured and expressed as (τ)=5E-13τ1/2
at the time range of 3.5s to 40 000s, which reached 2.6E-15 at the average time of 40000 seconds, and degenerated atlonger time due to the frequency drift of the H-maser, and the type-B uncertainty of the clock has been evaluated with thevalue of 2.4E-15. Several improvements have been realized on the clock, one was using an oven controlled crystal oscillator
as its local oscillator and locking the clock by directly feeding the error signal to the oscillator, so as to let the clock havestandard frequency signal outputs, in the research, we have demonstrated that the residual frequency drift of local oscillator
was at the level of 10-16-10-17, which would affect the frequency shift and uncertainty, as well as given the method ofcorrection, and which should be an universal effect for periodically running primary clocks. Another improvement waspointing out a method named as “self comparing” to evaluating the distributed cavity phase shift, collision shift, and lightshift, by comparing the errors of atomic fountain clock when which was alternately running in two different states, themethod evaluated the effects independently, not requiring any other comparing device, which the measuring precision of
better than the uncertainty of the clock.

IFCS-EFTF3-PAB3-9

Design and realization of a low phase gradient microwave cavity
for a continuous atomic fountain clock
Laurent Devenoges1, Gianni Di Domenico2, André Stefanov3, Pierre Thomann, Laurent-Guy Bernier1,
Jacques Morel1
12Federal Institute of Metrology METAS, Bern, Switzerland
Laboratoire Temps-Fréquence, Université de Neuchâtel, Neuchâtel, Switzerland
3
Institute of Applied Physics, University of Bern, Bern, Switzerland
Email: laurent.devenoges@metas.ch

Last year we presented measurements of the microwave phase gradients in the coaxial cavity of thecontinuous fountain clock FOCS-2 and we pointed out that the excitation of higher-order cavity
modes127 limited the performance of the clock at the level of 10-14.
We report here on the design, realization and performances of a low phase gradient microwave cavity
with two interaction zones. The resonator is composed of a ring waveguide of rectangular cross-section
with two independent feeds equidistant from the two interaction zones (see Fig 1(a)).
We fully characterized the amplitude and phase of the electromagnetic field in the microwave cavity

Fig. 36: (a) Scheme of the microwave cavity. The resonator is composed of a ring waveguide with twointeraction zones Z1 and Z2 equidistant from the feeding ports P1 and P2. (b) Cavity transmission
spectrum: measurement (black curve) is compared to finite element simulations (orange curve).

with the help of three-dimensional finite element simulations and analytical modeling. We predicted thatspatial phase variations of 30x10-6 rad may be reached over each interaction zone by balancing power
feeds128. To guarantee the phase homogeneity, the cavity has been machined with ultra-precision
diamond milling, providing tolerances of a few micrometers for dimensions of the ring waveguide withan excellent surface roughness of 15 nm. The effect of mechanical imperfections on phase gradients has
been extensively characterized with numerical simulations. After cavity assembly and tuning,measurements of the microwave spectrum (Fig. 1(b)) and the quality factor (Q 0=14’000) showed an
excellent agreement with finite element numerical simulations. Latest results and future perspectives of
the cavity performances will be presented.
127

A. Stefanov et al., “Finite element method evaluation of the phase gradient in a coaxial microwave cavity”, in preparation,
2013.
128

G. Di Domenico et al., “Low phase gradient microwave cavity with two interaction zones for a continuous atomic
fountain clock”, submitted to IEEE UFFC, 2012.

IFCS-EFTF3-PAB3-10

Preliminary Results of the Microwave Frequency Standard basedon 113Cd+ Ions
Jianwei Zhang1,2, Shiguang Wang1,3, Kai Miao1,2, Zhengbo Wang1,2, Lijun Wang1,2,3
1

NIM-THU Joint Institute for Measurement Science (JMI), Tsinghua University,
Beijing (100084), People’s Republic of China
2
Department of Precision Instruments, Tsinghua University,
Beijing (100084), People’s Republic of China
3
Department of Physics, Tsinghua University, Beijing (100084), People’s Republic of China
Email: zhangjw@tsinghua.edu.cn
In the past decades, frequency standards based on trapped ions have been widely investigated. A project
aimed at a microwave atomic clock based on the laser-cooled 113Cd+ ions has been carried out since2010 in our laboratory. This cadmium ion clock is expected to apply in the comparison between theclocks located in different places.
A linear quadruple ion trap and the technique of laser cooling are applied in this clock. The used laser
system is a frequency-quadrupled diode laser
system from Topitca Inc. To stabilize thefrequency of the laser to MHz level, the 858 nm
seed laser of this laser system is stabilized bycomparing the frequency with an 852nm laser
stabilized to the cesium lines via a transfer
cavity129. By the laser cooling, the ions can becooled down to crystallization state. In our
experiments,
itisdemonstratedthatapproximately 104 ions are cooled to 16 mK bylaser cooling130. Meanwhile, the frequency ofthe clock transition, the ground-state hyperfine
splitting of 113Cd+ ions, is measured131, and theresultis Fig. 37: Modified Allan deviation of the measured
15. 199 862 854 96(12) GHz.
data. The period of measurement time isRecently, the preliminary stability of this clock approximately 6 hours and the linear frequency drift
is removed.
is measured by the close-loop operation. Figure 1 shows the modified Allan deviation of themeasurement where the linear frequency drift is removed. Because the loop time constant here is about
100 s, the stability at the averaging time less than 100 s is from the local oscillator. The stability from100 s to 4000 s is approximately 1.5×10-12 τ-1/2. A series of upgrading of the experimental setup areplanned, and an improved result is expected in the next phase.
129

S.G. Wang, J.W. Zhang, Z.B. Wang, B. Wang, W.X. Liu, Y.Y. Zhao, L.J. Wang, “Frequency stabilization of a 214.5 nm
ultraviolet laser”, Chin. Opt. Lett., vol. 11, p.031401, 2013
130

S.G. Wang, J.W. Zhang, K. Miao, Z.B. Wang, L.J. Wang, “Cooling and crystallization of trapped 113Cd+ ions for atomic
clock”, Chin. Phys. Lett., vol. 30, p.013703, 2013
131

J.W. Zhang, Z.B. Wang, S.G. Wang, K. Miao, B. Wang, L.J.Wang, “High-resolution laser microwave double-resonancespectroscopy of hyperfine splitting of trapped 113Cd+ and 111Cd+ ions”, Phys. Rev. A, vol. 86, p.022523, 2012

IFCS-EFTF3-PAB3-11

Sub-mm scale optical fiber guided deep ultra-violet optical source
for trapped mercury ion clocks
Lin Yi, Eric A. Burt, Shouhua Huang, and Robert L. Tjoelker
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
Email: Lin.Yi@jpl.nasa.gov
Mercury ion based atomic frequency standards
provide practical advantages for spacecraft andground applications requiring reliable, stable and/or
compact atomic clocks [1-5]. In these standards, thesize and geometry of the mercury RF discharge lamp
used to generate 194 nm light and the related opticaldesign to deliver the light to the confined ion cloudare one of the key challenges towards simplificationand product commercialization.

Fig. 38: DUV discharge plasma generated in a

In this paper, we demonstrate the functionality of a 0.45mm capillary tube. The capillary tube is fused
mercury capillary lamp with a diameter in the sub- with a piece of fiber on the right.
mm range and Deep Ultra-Violet (DUV) radiationdelivery via an optical fiber integrated with thecapillary. DUV spectrum control is observed byvarying the manufacturing parameters such as buffer
gas type and pressure, capillary diameter, electricalresonator design, and temperature.
We will also show data for clock operation of the199
Hg+ hyperfine transition at 40.5GHz when applying
the above lamp and optical design. This new
approach towards a more practical UV optics
interface could benefit ion clock commercializationand trapped ion clock developments for deep spaceand GNSS.

Fig. 2: Linear ion trap incorporating an integrated
capillary lamp and fiber optic light delivery.
Mercury ions (light blue) are trapped along thenode created by the rods (grey) and endcaps (red).
The capillary lamp at the right is integrated withthe fiber (green) delivering DUV light (violet
cones) to the ion cloud through a small lens
(yellow).

IFCS-EFTF3-PAB3-12

Real Time Monitoring of the LNE-SYRTE Clock and Oscillator
Ensemble and Applications
M. Abgrall, B. Chupin, D. G. Rovera, J. Guéna, S. Bize, P. Rosenbusch, M. Lours, Ph. Laurent, A.
Clairon
LNE-SYRTE, Observatoire de Paris, UMR CNRS 8630, UPMC, Paris, France
Email: michel.abgrall@obspm.fr
The current LNE-SYRTE metrological ensemble includes an ultrastable frequency reference based on acryogenic sapphire oscillator (CSO) slowly phase locked on an H-maser. We have improved thereliability of our maser ensemble with the set up of two new ones. Three phase comparators
continuously measure the differences between our five H-masers.
The ultrastable reference is distributed to the other experiments located in laboratories a few 100 meters
distant from the CSO through compensated fiber links. The signal is transmitted to the three fountains
FO1, FO2 and FOM, and to the femtosecond lasers that allow connecting the strontium and mercury
optical lattice clocks to the primary frequency standards.
In this poster, we will present the data processing that we have implemented to monitor this clock
ensemble. Dedicated softwares hourly analyze the CSO loop and the fiber links data, to produce plots
and files of interval to be rejected due to abnormal behaviors. The fountain data are also processed every
hour. The raw data and parameters are uploaded from the fountain’s computers in order to estimate andapply the frequency shift corrections for each clock cycle. We then apply an averaging over 0.1 dperiods and a 3  filtering before computing the differences between the fountains on their synchronous
operation periods. Besides, using the masers comparisons, we also get the calibration of each maser
against the fountains. These processes including plots and alarm email generation facilitates thecontinuous survey of the operation of the clock ensemble and the detection of anomalies, necessary in
the framework of the PHARAO/ACES space mission. The processed data will also serve in the future
for the generation of a redundant UTC(OP) based on two different masers steered by the fountains.

IFCS-EFTF3-PAB3-13

Physics of systematic frequency drift of active hydrogen masers
with autonomous cavity auto tuning
Vasilyev V. I., Gavrilov V. V., Gorelov A. G .
Institute of Electronic Measurements KVARZ, Nizhny Novgorod, Russia
Email: nnipi_kvarz@sinn.ru
Systematic frequency change of a signal (drift) is one of the primary metrological characteristics ofhydrogen maser, but hypotheses about the drift nature so far have either qualitative or statistical anddescriptive property. The analysis of evolution is based on research of an asymptotics of relaxation
processes in quantum system132. As a first approximation the solution of the hydrogen maser differential
equations in a «stеady-state» approximation is used. The physical model of frequency drift is created;
the principles of drift minimization are discussed.
The results of theoretical research are compared with results of experiments and long-term practicalobservations over drift of a hydrogen maser 133. One of research conclusions is the statement that drift
can change the value and a sign.

Δf/f ,

×10-14

The importance of correct work of autonomous
cavity auto tuning system is theoretically andexperimentally proved. In Fig. 1 data on longcavity detuned
term measurements of frequency of our new
CH1-75B Active Hydrogen Maser model are
shown. This model can to tune the cavity with
controlled accuracy. In the figure evolution of
frequency of CH1-75B with the microwave
cavity tuned and detuned by +40 Hz arepresented. After cavity detuning the frequency of
cavity tuned
a maser was compensated by f f  110 12 .
After cavity detuning drift increased by 1.5
times from +1.3×10-15 to +1.9×10-15 per day.
MJD
Microwave cavity was again tuned 38 days later.
Frequency drift thus returned to its previous
Fig. 39: H-Maser CH1-75B – secondary standard of unit
value.
offrequency

VET1-20(InstituteofElectronic

The offered theoretical model allows to predict Measurements KVARZ) difference frequency. H-Maser
further behavior of maser frequency with the with the microwave cavity tuned and detuned by +40 Hz.
help of maser parameters monitoring.

132

Pestov E.N. Stability of relaxation processes in a quantum system as a main factor for achieving the long-term
frequency stability of a standard.// – Proc. of the joint conference IFCS/EFTF. – USA, San Francisco. –2011, pp. 623-627.
133

Vasilyev V.I., Gavrilov V.V. Investigation of systematic frequency drift of active hydrogen frequency standards //Proc. of the 6th International Symposium "Metrology of Time and Space". – Russia, Moscow. –2012, pp. 151-154.

IFCS-EFTF3-PAB3-14

Active H-maser with increase power of the output signal
To improve short-time stability the amplification of the hydrogen maser output
signal due to using the single-state selection and cooling the source cell istheoretically discussed. The results of the numeric calculation active H-maser
power versus magnet parameters of specific selective system and source
temperature are obtained. Particularly, the effect of increase maser power in
1.8 times due to amplification and elongation of selective system magnets isquantitatively calculated. Moreover, the output power is increased in 1.3 times
due to cooling the source cell to the room temperature. The quantitatively
comprasion between efficiency four-polar and six-polar magnets is done. In
conclusion, the theoretic prototype of maser, that has a short-time stability
achieved 2.48x10(-14) for one second, is represented.

IFCS-EFTF3-PAB3-15

A Waveguide Cavity for Miniature Rb Atomic ClockThomas Cao1, Leiji Liu2, Lin Yang3, Xingshi Zheng4
1

Spaceon Company, Chengdu, China
Email: sccyh@163.com

Rb atomic clock as a frequency standard is popularly used in the aspect of telecoms, electronic
instruments, etc., although Chip-Scale Atomic Clock (CSAC) based Coherent Population Trap (CPT)
has been manufactured two years ago. CSAC has tiny size and very low power dissipation, but thedisadvantages of high costs and lack of batch engineer applications in CSAC can not been surpassed in
short term. Alternatively, Rb atomic clock with traditional gas-cell has the advantages in costs and inpower dissipation, and has got improvements in reducing profile recent year. The means to reduce Rbclock dimension is mostly to design kinds of cavity, and some progress has been made in recent year.
Nowadays, introducing waveguide to the Rb clock cavity design, we have realized a novel miniature
waveguide cavity, and Rb clock with the cavity is lowered by three folders.
In order to stimulate clock transition in Rb clock, the H-component of the 6.8Ghz microwave signal
must be parallel to the quantum axes by C-field, and the level of the signal must be enough high. Except
for resonant cavity, a kind of circular tube waveguide with one cirque cover made by Efratom wasactually used in miniature Rb clock. But in this cavity, there is a difficult to tune its coupling ring which
is soldered with Step-Recovery-Diode (SRD), and thecoupling efficiency is very low by electronic vector.
While designing our waveguide cavity, we specially
set a screw slot to tune the cavity, and coupling ring
made with semicircular figure can transfer microwave
by magnetic vector. In this way, the screw slot acts asa relay-race to pass the microwave signal to Rb cell.
Therefore, the size of the cavity can be reduced atlarge extent, and microwave coupling efficiency can
get enough high simultaneously. With help ofsoftware simulation, the design has been approved.
According to the data, in the waveguide cavity, theefficiency climax is 6.8 GHz, and magnetic
component is parallel to the quantum axes, which
satisfy the design requirements. Especially, the highcoupling efficiency is from coordination between thesemicircular ring and the tuning screw, which is theshinning point in the design.
Fig. 40: the structure and the simulation of theInstead of traditional cavity, the waveguide cavity was miniature waveguide cavity. 6.8 GHz signal inputs
used in a typical Rb clock, and the similar Allan into the cavity, and a special traveling wave modelis shaped, the parallel H-component is enough high.
deviation of the clock has achieved. It means thenovel waveguide cavity with lower size than resonantcavity can be used in Rb clock. Recently, the traditional Rb clock compatible with OCXO has been
made with the cavity.

IFCS-EFTF3-PAB3-16

Experimental study on mutual injection locked VCSELs
Bozhong Tan1, Jiehua Chen2, and Sihong Gu1,2
1

School of Physics, Huazhong University of Science and Technology,
Wuhan, People’s Republic of China
2
Key Laboratory of Atomic Frequency Standards, Wuhan Institute of Physics and Mathematics,
Chinese Academy of Sciences, Wuhan, People’s Republic of China
Email: shgu@wipm.ac.cn
To exploit the better light source for the CPT atomic clock, we have developed a lin⊥lin quasibichromatic laser.134 Whereas the realized laser generator still does not suit for a practical package
atomic clock as a bulky optical isolator is used. Recently we have further explored a scheme that two
VCSELs are frequency mutual injection locked, and which does not need the optical isolator.135
However, there exist cavity modes problem as the two VCSELs form an optical cavity. We havesystematically studied the influence of cavity modes on the quality of the produced lin⊥lin quasibichromatic laser, and our experimental results reveal that with proper parameters the influence of cavity
modes can be well depressed, typical optical spectrum recorded under different parameters are present in
Fig.1(a) and Fig.1(b). We have applied the lin⊥lin quasi-bichromatic laser of Fig.1(a) in CPT resonanceexperiment and obtained high quality CPT resonance signal. It is promising to realize a package lin⊥lin
quasi-bichromatic laser generator and apply it in the package CPT atomic clock.

0.070

6.8GHzOptical Power(unitary unit)

Optical Power(unitary unit)

0.070
0.065
0.060
0.055
0.050

0.045
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Optical Frequency(unitary unit)

(a)

0.065

0.060

0.055

0.050
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Optical Frequency(unitary unit)(b)

Fig. 41: The optical spectrum of two VCSELs’ ouput recorded by Fabry-Perot
interferometer. The injection ratio is (a) 0.5% , (b) 2.2%.

134Peter Yun, Bozhong Tan, Wei Deng, Jing Yang and Sihong Gu, “Quasi-bichromatic laser for lin⊥lin coherent population
trapping clock produced by vertical-cavity surface-emitting lasers”, Rev. Sci. Instrum. vol.83, p.093111, 2012.
135 Bozhong Tan, Peter Yun, Jing Yang, Yuan Tian, Sihong Gu, “A chip scale lin⊥lin quasi-bichromatic laser scheme”,
submit.

IFCS-EFTF3-PAB3-17

Effect of the coherent population trapping on saturated
absorption resonances in Cs vapor
Ersoy Şahin1, Ramiz Hamid1 and Azad Ch. Izmailov2
National Metrology Institute of Turkey, Gebze, Kocaeli, TURKEY
2
Institute of Physics, Azerbaijan National Academy of Sciences, H. Javid av. 33, Baku, Az-1143,
AZERBAIJAN
Email: ersoy.sahin@ume.tubitak.gov.tr
We have detected and analyzed sub-Doppler resonances in absorption of the monochromatic probe lightwave interacting with the counterpropagating bichromatic laser beam in the rarefied Cs vapor. Given
photoprocesses were realized on resonant 3-level Λ-systems formed by spectral components of the
Doppler broadened D2 line of cesium atoms.
The scheme of our setup is shown in Fig.1. The diode laser generates the monochromatic laser beamwith the scanned frequency ω1. The second coherent radiation component (with the frequency ω2) was
obtained from the initial beam by the electro-optical modulator. The frequency difference (ω1 − ω2) wasstabilized near the microwave interval Δ≈9192.6 MHz between hyperfine sublevels of the Cs ground term.
1

Fig.1. Scheme of the experimental setup, which includes external cavity diode laser (ECDL), electro-opticalmodulator (EOM), beam splitter (BS), mirrors (M1, M2, M3, M4), polarizers (P1, P2), quartz windows (QW1,
QW2), neutral density fitler (ND), photodiode (PD) and the Cs cell with the magnetic shielding

Sub-Doppler saturated absorption resonances of the probe beam were recorded versus the scanned laser
frequency ω1 at various fixed values of the frequency difference (ω1 − ω2) and intensity of the bichromatic
pumping beam (having the same parallel linear polarization). By this applied method, we have established theessential dependence of given sub-Doppler resonances on the frequency difference (ω1 − ω2) in its narrowinterval (<1MHz) around the hyperfine splitting Δ≈9192.6 MHz. According to our analysis, given interesting
features are caused by displays of the coherent population trapping1 on resonant 3-level Λ-systems interactingwith counterpropagating pumping and probe beams. Obtained results of this work may be used for
optimization of laser frequencies stabilization on atomic transitions.
_____________________________
1

E. Arimondo, “Coherent Population Trapping in Laser Spectroscopy”, Progress in Optics (Elsevier, New York, 1996), Vol.
35, 257-354.

IFCS-EFTF Group 4 poster session 1
Forum Hall
Monday & Tuesday, July 22-23, 2013, 01:00 pm - 02:00 pm and 3:30 pm - 4:30 pm
Chair:Paul Muralt
EPFL

IFCS-EFTF4-PAB4-1

Wireless temperature sensingof fast rotating objects
R. Fachberger*, C. Werner**

Sensideon, Wels, Upper Austria/Austria
Email: funk@sensideon.com

A surface acoustic wave (SAW) transponder system was developed to measure the temperature andoptimize the heat flow within a continuously variable transmission (CVT) gearing of a combustion
engine. Though no external trigger is used, temperature measurements on the rotating parts have beenrealized up to a rotational speed of 8.000 rpm.
Temperature sensing of fast rotating objects is needed to optimize temperature critical parts or to findthe operational limit of certain components within high speed engines. SAW transponder systems arewell suited for such sensing applications, as they can be interrogated wirelessly136.
In the paper a SAW sensing system for temperature measurement of fast rotating objects is described.
The system was developed to measure the disk temperature of a CVT gearing. This temperature is
critical due to possible heat transfer to the gearbelt. The systems works without an external
trigger and can be attached with minimal effort.
The temperature of the disk was measured up to a7000 rpm
rotational speed of the CVT disk of 8.000 rpm(Fig. 1). In the laboratory temperature
measurements have been realized up to a
6000 rpm
1200 rpm 2000 rpm
rotational speed of more than 30.000 rpm.
100

temperature (°C)

90

80

70

60

5000 rpm

3000 rpm
For a good thermal coupling the SAW sensor was
4000 rpm
directly attached to the CVT disk. Via a coaxial
cable the radio frequency signal was transmitted
from the SAW device to the transponder antenna, 21.11.2012 11:37 21.11.2012 11:39 21.11.2012 11:42 21.11.2012 11:44
screwed onto the CVT gearing. All transponder
parts have been locked with an epoxy adhesive, to Fig. 42: Measured temperature of the fast rotating
CVT disk
ensure a good bond to the fast rotating gearing. A
specialized transponder antenna was designed andmatched to the metal surrounding and the SAW device to achieve a good sensor signal. Aspects of thesystem design and the measurement results are presented.
50

40

136

A. Binder, R. Fachberger, “Wireless SAW temperature sensor system for high-speed high-voltage motors,” IEEE Sensors
Journal, vol. 11/4, pp 996 – 970, 2011

IFCS-EFTF4-PAB4-2

Packageless temperature sensor based on AlN/IDT/ZnO/Siliconlayered structure
Ouarda Legrani1, Omar Elmazria1, Meriem Elhosni1, Sergei Zhgoon2,
Ausrine Bartasyte1 and Philippe Pigeat1
1

2

Institut Jean Lamour, UMR 7198 Université de Lorraine – CNRS, France
Moscow Power Engineering Institute, 14 Krasnokazarmennaja, 111250 Moscow, Russia
Email: ouarda.legrani@ijl.nancy-universite.fr

In previous works we have shown theoretically and experimentally [1], [2] the possibility to generate
simultaneously Surface Acoustic Wave (SAW) and Waveguiding layer acoustic wave (WLAW) inlayered structures AlN/ZnO/diamond [1] and AlN/ZnO/Silicon [2]. Such structures are of great interest
because of their potential applications as packageless resonators, filters or sensors, based on WLAW,
and as thermally compensated gas or liquid sensors, based on the combination of both SAW and
WLAW. The aim of this work is to evidence the potential of the AlN/ZnO/Silicon structure as low cost, CMOS

S21 (dB)compatible and packageless temperature sensor able to operate at harsh environments.
2µm thick ZnO films were deposited on (100) Si by RF magnetron sputtering. IDTs were fabricated on
ZnO/Si surface by sputtering aluminum followed by photolithography and wet etching processes. The AlN
protection layer of 30 µm thick, deposited by RF magnetron sputtering, was optimized in order to avoid the AlN
film cracking. A delay line operating at 525 MHz was obtained and tested versus temperature in air and in contact
with liquid. Experimental characterization was compared to modeling with commercial software (COMSOLMultiphysics). The full sized delay line was simulated and the liquid was modeled by an additional layer on the
top of AlN film. The effective confinement of the wave was shown by deposition of water’s micro drop on thedevice and confirm by modeling.
Frequency-Temperature characteristic shows a very
good linearity and a TCF value of -19ppm/°C in air and-20
in contact with liquid. One can also observe that there-30
is no change in transmission responses (S21) collectedin both conditions (Fig. 1). These results prove the total-40
confinement of the wave in the AlN/IDT/ZnO/Si
structure which is confirmed by 2D FEM modeling.
-50
Note that a Rayleigh wave on open surface is partiallyor completely attenuated. This study confirmed the-60
feasibility of the AlN/IDT/ ZnO/Si structure as-70
packageless sensor sensitive to temperature with theability to protect itself from undesired environment
before micro-drop deposition-80
after micro-drop deposition
effects such as humidity, gas corrosif or not, liquid, ...
480

500

520

540

560

580

Frequency (MHz)Fig. 1: Test of the wave confinement by the deposition of awater micro-drop on the AlN/ IDT/ZnO/Si structure.

[1] O. Elmazria et al., Applied Physics Letters, vol. 95,
p. 233503, 2009.
[2] O. Legrani et al. ; IEEE sensor Journal, vol. 13, p. 487-491, 2013.

IFCS-EFTF4-PAB4-3

Piezoelectric and electroacoustic properties of V-doped and Tadoped AlN thin films
1

E. Iborra1, V. Felmestger2, M. Mikhov2, J. Capilla1, J. Olivares1, M. Clement1
GMME-CEMDATIC-ETSIT, Universidad Politécnica de Madrid, Madrid, Spain
2
OEMGroup Inc., Gilbert, AZ, USA

Email: eiborra@etsit.upm.es
New piezoelectric thin films for electroacoustic applications are being currently developed. AlN-based
ternary compounds are expected to possess better properties than conventional AlN, such as larger
piezoelectric activity, thermal stability of frequency and temperature resistance. The effect of adding Cr,
Sc, Mg, Ti and B to AlN films has been previously investigated. Tantalum and vanadium are transition
elements that can fit the oxidation level to substitute Al in the wurtzite AlN structure; their different
ionic radii allow predicting changes in the AlN lattice structure and thus in the piezoelectric properties.
In this communication we investigate the properties of Al(1-x)VxN and Al(1-x)TaxN compounds forelectroacoustic device applications.
1 µm-thick Al-X-N films (X = V or Ta) were reactively sputtered on 150 mm-Si (100) wafers using adual target ac (40 kHz) powered S-gun magnetron. For this study, the two concentrically-nested ringshaped targets were made of pure Al and pure X material. The power applied to each target could becontrolled separately. The Si wafers were placed directly above the target array, which provided Al-X-N
films with a gentle radial gradient of the X concentration. For electroacoustic test devices a very simple
acoustic mirror made of a SiO2/Mo/Al stack was used under a Mo/Al-X-N/Mo piezoelectric sandwich.
The wafers were cut radially into 75 mm-strips, which were characterized at different points each 1 cm.
The properties of the films were investigated as a function of their composition, measured by Rutherford
backscattering spectrometry. The microstructure and morphology films were assessed by X-ray
diffraction and infrared reflectance. Their electroacoustic properties and dielectric constant were derived
from the frequency response of BAW test resonators built along the strip and separated by 1 mm.
The piezoelectric characterization through the test resonators reveals that all the samples investigatedexhibit a significant decrease of the piezoelectric activity as compared to pure AlN films. Only the films
containing the smallest amounts of V showed piezoelectric activity, although they hardly reach values ofthe electromechanical coupling factor keff2 of 2.4%. XRD measurements suggest that V does notincorporate homogeneously in the AlN lattice and a slight variation of the c lattice constant has been
detected. Films with the highest V content (around 5% atomic) exhibit an increase of the electricalconductivity. As for Ta doped films, the larger keff2 of 4% corresponds to the film with the lowest Ta
content. The decrease of keff2 is accompanied by a reduction in the sound velocity of the longitudinalmode and an increase of the dielectric constant ranging from 10% to 20%. Structural characterization
reveals that Ta distributes homogeneously in the AlN lattice and increases its c lattice constant up to
25%. The poor piezoelectric activity of Al-X-N films cannot be justified only by the presence of small
amounts of impurities. The appearance of shear resonances as we move towards the edges of the wafers,
along with the presence of a disordered layer developed during the early stages of growth revealed by
XRD, suggest the presence of tilted grains in the films, which is more pronounced in Al-V-N films. Thishas been previously associated to growth of grains with opposite polar orientation, which would accountfor the lowering of the piezoelectric response. Further sputter process optimization is required to address
the technological aspects of the film crystallinity and enhance the piezoresponse.

IFCS-EFTF4-PAB4-4

Evaluation of the acoustical properties of adhesive-free dual layer
piezoelectric PVDF copolymer Transducer
Adit Decharat, Sanat Wagle and Frank MelandsøDepartment of Physics and Technology, The University of Tromsø, N-9037 Tromsø, Norway
Email: adit.decharat@uit.no
Multiple layer of piezoelectric copolymer transducer has been deployed to improve the performance oftransducers since their mechanical coupling efficiency are relatively low compare to ceramic transducer.
Traditionally, to fabricate multilayer polymer transducers from pre-polarized film, adhesive layers areused for increasing their stack layers, which require mechanically attaching process where the desiredand consistent thickness of each adhesive layer are difficult to achieve. Such condition, consequently,
caused reduction of overall acoustic response signal137. As far as we know, only one group has
previously produced an adhesive-free multilayer transducer with few publications138. Therefore, there isa need for comparative evaluations on the modeling with experimental result of an adhesive-freetransducer.
In this study, we present the simulation and experimental results of the adhesive-free dual layer
ultrasonic transducer. Using copolymer polyvinylidene fluoride trifluoro ethylene P(VDF-TrFE) in thefluid form together with commercial fabrication processes like spin coating, mask lithography andchemical etching etc., the dual layer transducer stacks were fabricated directly onto a Polyethyleneimine(PEI) backing unit. A FEM software (COMSOL Multiphysics) was employed to simulate the acousticalproperties of the transducer. To characterize the transducer, the acoustic backscattering measurementfrom the backing-air interface was performed by exciting the transducer with ultra-wideband pulse(UWB) with various pulse widths. Transducer electrical impedance as function of frequency was also
obtained by using an impedance analyzer.

Intensity

The amplitude of the acoustical response from thebackscattering measurements was for most cases
bothsignificantly higher, when the transducer was
0.02
upper
0.006
lower
0
excited and received signals from the both layers-0.02
compared to a single one as shown in Fig. 1.
0.004
Moreover, smooth broad-band acoustic signals
2.1
2.2
2.3
2.4
2.5
Time, t (s)were also measured. The simulated pulse echo
0.002
response of the dual layer transducer undervarious pulse width excitation signals were
calculated and compared from the experimental
0
20
40
60
80
results, which showed good agreements. The
Frequency, MHz
simulation and fabrication processes were foundto be beneficiary for the further analysis ofFig.1: Acoustic reflection from backside of PEI
multiple stacking of PVDF copolymer to enhancebacking(smallwindow)andthe acoustical performance.
corresponding frequency spectrum.
137

Q. Zhang , P. A. Lewin and B. P. E. “PVDF transducers - A performance comparison of single layer and multilayer
structures”, IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 44, pp.1148 -1156, 1997.
138

T. Lilliehorn, T. Blom, U. Simu, S. Johansson, M. Nilsson, M. Almqvist,
transducers”, Proc. of 2005 IEEE Ultrasonics Symposium 3 (2005) 1618 – 1620.

“Multilayer piezoelectric copolymer

IFCS-EFTF4-PAB4-5

Software Defined Radio for Passive Sensor Interrogation
J.R. Humphries and D.C. Malocha
Department of Electrical Engineering and Computer Science
University of Central Florida, Orlando, FL, USA
Email: James.Humphries@knights.ucf.edu
The software defined radio (SDR) provides a unique platform for interrogating passive, wireless SAW
sensors. We have explored a commercially available SDR, the universal software radio peripheral(USRP), developed by Ettus Research. The highly versatile USRP platform defines many interrogator
functions in software rather than hardware. The system provides a cost effective manner to develop a
prototype transceiver (passive tag reader), and allows both internal FPGA programming and custom postprocessing software by the user.
This SDR design approach uses the N200 USRP and WBX daughterboard, providing center frequency
tuning between 50MHz and 2.2GHz with +20dBm output power. The USRP hardware driver (UHD) isutilized to provide the software interface between the host computer and N200. GNU Radio, an opensource DSP and software radio library, is also employed for signal generation and post processing. The
system allows the user to define the desired center frequency and sensor interrogation signal (chirp orother) of the transceiver. This information is passed to the USRP, which handles the transmission of thesignal samples as well as acquiring the sensor responses. The data is returned to the host PC for postprocessing and data extraction.
The USRP capabilities are demonstrated by interrogating multiple orthogonal frequency coded (OFC)139
SAW temperature sensors at 915MHz. Since OFC is a spread spectrum coding technique (>20MHz
bandwidth) and since synchronization is required for passive sensor signal averaging, the USRP FPGA
code was modified to handle the TX and RX independently from the host computer. This is in contrast
to the default operation where signal sampling is accomplished over Ethernet. Characterization of thesystem is given with respect to SNR, output power, minimum detectable signal, and noise figure. Sensor
range measurement experiments are also provided to characterize output power and signal averaging
efficiency.
Passive Sensor
Tags
TX

RX

USRP
USRP Control / Post Processing

Figure 43: The N200 USRP (Center) is utilized to interrogate passive, wireless sensor tags (right). The center frequency andbandwidth of the transmitted output signal is defined by the user on the host computer (left). The USRP then independently
handles transmitting the interrogation signal and receiving the sensor responses. Post processing of the data on the PC allows for
signal averaging and data extraction.
139

Malocha, D.C.; Puccio, D.; Gallagher, D., "Orthogonal Frequency Coding for SAW Device Applications," Ultrasonics
Symposium, 2004 IEEE , pp. 1082- 1085 Vol.2, 23-27 Aug. 2004

IFCS-EFTF4-PAB4-6

Induced surface roughness to promote the growth of tilted AlN
films for shear mode resonators
Mario de Miguel-Ramos, Marta Clement, Jimena Olivares, Jose Capilla, Jesús Sangrador, Enrique
Iborra
GMME-CEMDATIC-ETSIT, Universidad Politécnica de Madrid, Madrid, Spain
Email: eiborra@etsit.upm.es
A serious drawback of biochemical sensors based on piezoelectric resonators is the requirement ofoperating in liquid environments. This can be overcome by exciting shear modes that exhibit lessattenuation in liquid media than longitudinal modes. Shear modes can be excited in AlN-based
resonators as long as that the films exhibit grains tilted with respect to the surface normal. These arecommonly achieved by off-axis sputter deposition on rough substrates, since AlN microcrystals tend togrow normal to the surface whatever its topography. To achieve the desired tilt, a good control of theslopes of the substrate topography is required. The required roughness can be developed either in theunderlying layers before the growth of the AlN film, or directly in the AlN deposition process bycarrying out its growth under high pressure during the first stages, thus promoting the development of athin layer of randomly oriented grains, which are the seed for the growth of the tilted AlN microcrystals.
In this communication we analyze the influence of the substrate surface structure and the deposition
parameters on the crystalline orientation of the AlN films and, hence, on the frequency response of shear
mode resonators.
AlN films were deposited at 350°C in an UHV sputtering system on silicon substrates covered with
Bragg mirrors composed of Mo andporous-SiO2 layers. The first set of AlN
films
with tilted-grains was achieved byadjusting the roughness of the uppermost
SiO2
layer by varying the deposition conditions.
The
SiO2 layers were assessed by AFM andcovered afterwards with a Mo or Ir bottom
electrode before growing the AlN film.
The
second set of films was achieved bydepositing at high pressure a non-oriented
AlN
seed layer on the bottom electrodes. In thiscase,
the Bragg mirrors had been previously
polished to remove the influence of theirroughness.
X-ray diffraction, infrared reflectance, AFM and electrical characterization were used to assess theinfluence of the seed layer structure and the deposition parameters on the tilt angle, the crystal quality
and the shear mode frequency response of the AlN-based resonators. Depending on the roughness andnature of the seed layer, a controlled tilt varying from 0º to 30º was achieved. The frequency variation of
the electrical impedance was fitted using Mason’s model for both longitudinal and shear modes, whichallowed us to derive the electromechanical coupling coefficient ks2 of the shear mode and its acoustic
velocity. Values of ks2 as high as 2.4 % and an acoustic velocity of 6450 m/s were obtained in AlN films
with 20° tilted grains deposited on rough SiO2 substrates (see figure). Rough AlN seed layers provided
values of ks2 up to 2% with great reproducibility. Preliminary in-liquid tests are also presented.

IFCS-EFTF4-PAB4-7

GNURadio as a digital signal processing environment: application to acoustic
wireless sensor measurement and time & frequency analysis of periodic signals
J.-M Friedt1
1

SENSeOR, c/o FEMTO-ST Time & Frequency, UMR CNRS 6174, Besançon, France
Email: jmfriedt@femto-st.fr

Digital signal processing has gained growing interest with respect to analog processing due to its
reconfigurability, stability and flexibility. Thanks to these properties, a given hardware operating
condition can be tuned as a function of operating mode (initialization, continuous mode or standby),
whatever the environmental conditions (as opposed to resistor value dependence with temperature orcapacitance with moisture levels) or as a function of the targeted application at the prototyping stage.
Software Defined Radio is interested in the application of digital signal processing methods toradiofrequency signals, amongst which lie the frequency range of the devices of interest to the time andfrequency community.
Although dedicated hardware and software has been demonstrated as functional for phase noisecharacterization of stable oscillators, no general purpose toolbox has been provided towards the time &frequency community for digital processing of the recorded signal in real time. In this presentation, we
consider the GNURadio software environment as a suitable tool both for teaching and getting acquainted
with the basics of digital signal processing applied to time & frequency characterization of periodic
signals, but also as a framework for efficiently recycling the implemented algorithm on a wide range of
hardware and thus on a wide range of frequencies. Indeed, the signal source supported by GNURadio
range from the audio frequency sound card (<100 kHz signals) to the 100-MHz UHD provided by Ettus
Research, to the Digital Video Broadcast (DVB) receiver USB dongles compatible with the low costrequirements of teaching. Most significantly, this opensource framework allows any interested user to
add his own source and sink as peripherals whose data flow then become compatible with the processing
flow already implemented.
In this presentation, we introduce the basic concepts of GNURadio, first from a user perspective witheither the programming of signal processing chains written in the Python language or generated using
the graphical user interface GNURadioCompanion. Then, we demonstrate how dedicated signal
processing blocks, first prototyped in an interpreted language (GNU Octave or Matlab), are included
within the GNURadio framework. We are interested in using existing GNURadio processing blocks forreal time control and processing signals recorded from an implementation of a 2.45-GHz FMCW
RADAR140 used for probing acoustic delay lines acting as passive sensors interrogated through awireless link, and for providing basic signal processing tools such as frequency counting and phase noise
spectra. We demonstrate consistency between measurements from digital implementations of thesealgorithms and the classical measurement obtained with analog tools.

140

inspired from MIT’s Small Radar System course at http://ocw.mit.edu/resources/#LincolnLaboratory

IFCS-EFTF4-PAB4-8

Modeling and Analysis of a Liquid-Level Sensor Utilizing an
Evanescent Field of a Trapped-Energy Vibrator
Ken Yamada, Tatsuya Ishioka, Naoki Aita
Department of Electronic Engineering, Tohoku Gakuin University,
Tagajo, Miyagi, Japan
Email: k-yamada@tjcc.tohoku-gakuin.ac.jp
A novel approach for detecting a small-scale variation in liquid level that employs a piezoelectric
thickness vibrator operating in a trapped-energy mode has been studied by the authors141,142,143. In atrapped-energy resonator, an evanescent field is created in the surrounding (unelectroded) region inwhich the vibration amplitude decays exponentially. If the evanescent region is dipped in a liquid, adepth-dependent leakage of vibration energy will occur and this causes the deterioration in themechanical quality factor Qm and/or the electric conductance G. Because the liquid level is detected byobserving variation in G of the resonator, it is desirable for simulating its operation that the sensing
device should be modeled by an equivalent electric network.
In this study, the sensor is modeled by modifying an equivalent electric network proposed byNakamura et al. which could represent the propagation of a thickness-vibration mode along thepiezoelectric plate. Figure 1 shows the network model144 for the sensing vibrator with a thickness of 2H.
The central electroded region is composed of a transmission line (length: 2l, characteristic impedance:
Z0, wave number: γ) which is related to the electric terminal via some additional elements including adamped capacitance C0. The section between the electrode edge and the liquid surface is expressed by atransmission line representing the unelectroded portion of length 2d, wave number γD and characteristic
impedance Z0D. The outermost regions are supposed to have an infinite length and are therefore
expressed by the characteristic impedance Z0D. To take the radiation loss into account, a phase angle -δ isapplied to Z0D for the portion dipped in a liquid. The variation in the electric properties with the dipping
depth is evaluated for several geometry of the sensor by varying the ratio d/H.
Figure 2 shows an example of the variations in G with the liquid level d/H at the resonancefrequency of the fundamental and inharmonic overtone modes. The ratio l/H is 9, and the admittancecharacteristic computed for the unloaded plate is shown in the inset. It is shown that the sensing
property varies depending on which one of the fundamental and overtone mode is used.

Fundamental

2nd overtone

1st overtone

Fundamentalst
1 overtone
2

Fig. 1 Liquid-level sensor and network model

141

143

overtoneFig. 2 Variations in G with the liquid level at resonance

K. Yamada, H. Honda, S. Horiuchi, and T. Kinai: Jpn. J. Appl. Phys. 48 (2009) 07GB08.
K. Yamada, S. Horiuchi, H. Honda, and T. Kinai: Proc. 2009 IEEE Ultrason. Symp., p.2508.
K. Yamada and S. Seto, and S. Horiuchi: Proc. 2011 IEEE Ultrason. Symp., p.1522.
144
K. Yamada, T. Koyama, and S. Seto: Jpn. J. Appl. Phys. 51 (2012) 07GC04.
142

nd

IFCS-EFTF4-PAB4-9

THE GaPO4 BIOSENSOR´S AFFINITY AND ITS ELECTRONIC EVALUATION
Milan Kolář and Jaroslav Nosek
Technical University of Liberec
Faculty of Mechatronics, Informatics and Interdisciplinary Studies
Studentska 2, CZ-461 17 Liberec, Czech republic

Abstract - This paper deals with the formation of the ASC immunocomplex at the surface of the Y-cut
GaPO4 resonator vibrating in thickness-shear mode. The three different orientations YXl (0.0°), YXl (11.0°), and YXl (-16.4°), with the tolerance on the rotation angle  0.1° of the samples, are used in thisstudy. The relevant GaPO4 material constants were calculated.
The biochemical affinity process can be characterized by association and dissociation kinetic rate
constants, by binding between a covalently immobilized small molecule and its relative antibodies. The
binding curves of series resonance frequency fs vs. time t were measured and discussed. The following
tasks were considered: activation by the cystamine, glutaraldehyde, and albumine as bioactive buffer,
ASC antibody solution with phosphate buffer, and regeneration of the biosensor.
Standard frequency response of a new biosensor was evaluated by the analyzer Agilent E5100A.
However, the newly developed digital processing techniques are used to precise the measurement andto evaluate the frequency changes. The Field Programmable Gate Array circuits (FPGA) open the fieldof digital signal processing. Our solution used the digital down converter (DDC) for evaluation of
frequency changes. The DDC consists of three components: reference complex oscillator, low-passfilter and down sampler. Complex (quadrature) oscillator works on principle of direct digital synthesis
and it provides a pair orthogonal sine and cosine waveform. The complex multiplier works as mixer, its
output includes images centered at the sum and difference of input frequencies. The low-pass filter isdigital FIR filter and it passes the difference frequency. The down sampler reduces the sampling rate ofa signal.
The digital solution gives important advantages – digital stability, controllability and small size, thatallow to realize the biosensor controller unit in a smaller volume. This solution reduces the cost of thebiosensor unit and bringing it closer to the solutions "lab on chip". However, a resolution of thebiosensor was maintained.
Keywords: GaPO4 biosensor, ASC formation, FPGA circuits, evaluation of frequency changes

IFCS-EFTF Group 5 poster session 1
Forum Hall
Monday & Tuesday, July 22-23, 2013, 01:00 pm - 02:00 pm and 3:30 pm - 4:30 pm
Chair:

Philip Tuckey
LNE-SYRTE, Paris Observatory

IFCS-EFTF5-PAB5-1

Frequency Stability Estimation of Compass On-Board Clock
Based on Smoothed Broadcast Ephemeris
Hang Gong1, Wenke Yang1, Zengjun Liu, Xiangwei Zhu1, Feixue Wang1
1

Satellite Navigation R&D Center, School of Electronic Science and Engineering, National Universityof Defense Technology, Changsha, Hunan 410073, China
Email: gonghang@nudt.edu.cn

Short-term frequency stability of on-board clocks is of paramount importance to GNSS applications,such as clock modeling and clock offset prediction. The ODTS method, which is well-known andcommonly used, needs continuous observation from large monitoring networks and complex algorithms.
BeiDou Navigation Satellite System (BDS/Compass) and Galileo are in their early stage of construction
and do not have worldwide observation networks to track the satellite continuously. In addition, limitedaccess permission has also restricted the common users from obtaining precise on-board clockparameters.
10-11Overlapping Allan Deviation y()Based on the analysis of single station estimation
method of satellite on-board clock stability, this paper
10
proposed a simple estimation method based onsmoothed broadcast ephemeris (namely SBE method),which only needs observation from one single receiver.
BE
10
SBE
The principle of this method is discussed, followed byPE
IGS
performance evaluation using GPS data. Compared to
10
10
10
10
10
IGS final clock product and other two methods namely
Average Time  (s)PE and BE method, the performance of this method is Fig. 44: Frequency stability of GPS PRN14
validated (Fig.1). We conclude that the relative estimation result comparison among BE, PE
estimation error of this method is less than 10% for the and SBE Method
average time of 1~800 seconds, which is consistent withthe results of PE method using precise ephemeris.
-12

-13

0

Overlapping Allan Deviation y()

10

1

2

3

4

-11

Finally, the short-term stability of all the current
Compass on-board clocks (until December 2012) are
estimated by the proposed method (Fig.2), the results
show that the stability of all the satellite clocks are
consistent and agree well with ODTS results. The shortterm stability of current Compass on-board clocks isapproximately 6×10-12(τ=1s), 2×10-12(τ=10s), 5×1013
Fig. 2: Frequency stability of all the current(τ=100s), 2×10-13(τ=1000s).
10

10

10

-12

SV01
SV03
SV04
SV05
SV06
SV07
SV08
SV09
SV10
SV11
SV12
SV13
SV14

-13

-14

10

0

10

1

2

10
Average Time  (s)

10

3

10

4

Compass on-board clocks estimated by SBE

This proposed method in this paper provided some Method
meaningful suggestions of short-term frequency
stability estimation and simulation of on-board clock for Compass and Galileo civil users. When thesatellite on-board clock stability is better than receiver clock, the method also provides a receiver clockstability estimation approach. In addition, since the method could calculate the short-term stability of thesatellite clock in real-time directly using broadcast ephemeris and monitoring receiver’s observation, it
is also valuable for integrity monitoring and online performance assessment of satellite on-board clock.

IFCS-EFTF5-PAB5-2

The Test and Evaluation of GPS On-board Clock
Yongliang XU1,2, Wei LI1,2
12

National Time Service Center, Xi’an, China

Key Lab of Time and Frequency Standard of the Chinese Academy of Sciences
Email:xuyl@ntsc.ac.cn

Abstract: In satellite navigation system, the mainly time-frequency equipment of space segment is onboard clock, and its performance directly related to the pseudo code ranging and doppler effectobservation precision, then affects the satellite navigation system orientation, velocity measurement andtime service, so the test and evaluation of the on-board clock attach much importance. The on-board
clock performance evaluation experiment had been done many times in the GPS, GALILEO andGLONASS satellite navigation systems. The similar research and experiment are carrying out in
Chinese satellite navigation system.
This paper studies the indicators used to evaluate the on-board clock, including the definition andcalculation model of accuracy and stability. The performance of GPS on-board clock is evaluated basedon the GPS on-board clock time difference data released by the IGS. Using Hadamard variance toevaluate the stability, the results show that the stability a day of most GPS on-board rubidium atomic
clocks can reach 2  10 14 , in the time interval of 5 days, the stability reaches the highest level.
Keywords: On-board clock, evaluation, accuracy, stability

IFCS-EFTF5-PAB5-3

An FPGA implementation of the Distributed RF over White Rabbit
Pedro Moreira1, Javier Serrano2, Pablo Sanchez2, Tomaz Wlostowski2, Izzat Darwazeh1
1Electronic & Electrical Engineering, UCL, London, United Kingdom
2
BE/CO/HT, CERN, Geneva, Switzerland
Email: pedro.moreira.09@ucl.ac.uk

Previous works have demonstrated modeling verification of the signal acquisition and processing blocks
implemented by the distributed RF over White Rabbit (WR) system architecture and their effect on the
SNR and Phase-Noise of the distributed RF signalxiii. This novel architecture relies on the White Rabbit
network (an Ethernet based network with sub-nanosecond timing accuracy specification) to distribute an
RF signal over distances that can reach 10 km using relatively low network bandwidth. Thus, theremaining network’s bandwidth can be employed to transmit other control or non-control data.
To validate its real performance in a realistic scenario, this paper describes an FPGA implementation of
the distributed RF scheme. In addition, characterization the reconstructed RF is given by showing
measurements of the reconstructed RF signal phase-noise spectrum and Allan deviation. The paper
continues with a description of the frequency drift and offset between the original and reconstructed RF
signal.
Figure 1 and 2 shows the block diagram of the hardware implementation for the transmitter and receiver
nodes of the distributed RF architecture.

Figure 45 - Transmitter Architecture

Figure 46 - Receiver Architecture

The results obtained from the presented FPGA system implementation confirm that the proposed
distributed RF architecture is a low cost solution suitable for the distribution of RF signals. The RF
signal can be distributed over relatively large distance using non-dedicated links and still reach therequired SNR and phase-noise performance.

IFCS-EFTF5-PAB5-4

Calibration System For Stopwatches
1,3

A. Sahar , E.F. Dierikx2, R.P. van Bemmelen2, R.P. van Otterloo2, M. Fauzi 3, M. Nasir1
1

NML, SIRIM Berhad, Bandar Baru Salak Tinggi, 43900 Sepang, Malaysia
23VSL, Thijsseweg 11, NL-2629 JA, Delft, Netherlands

Faculty of Electrical Engineering, University Technology of Malaysia,
81310 Skudai, Johor, Malaysia
Email: ahmads@sirim.my

Stopwatches and other similar timing display devices can be calibrated using three methods: the directcomparison, the totalize method and the time base method1. In the time base method, the frequency of
the time base of the stopwatch, typically a quartz oscillator is measured directly. The time base method
has a smaller measurement uncertainty than the other two methods.
In 2012, NML, SIRIM Berhad has developed an in-house designed calibration system for timing devices
with displays that have digital seven segment characters on its display. The new system developed isbased on an optical sensor and a dual counter.
DISPLAYDISPLAYAn optical sensor (Fig.1) is directed to one of
the seven segment characters of the LCD
1 COUNTER
2 COUNTER
timing display of the stopwatch. When the
stopwatch is free running, the counters will
OPTICAL
TRIGGERING
read the segments and take turns on counting
CIRCUITSENSOR
10 kHzthe pulses of the 10 kHz reference frequency.
The counted pulses are displayed in seconds.
stndFig. 1. Stopwatch calibration setup at NML, SIRIM

To evaluate the performance of the NML’s calibration system, method used and technicalcompetence, a bilateral comparison was organized with the national metrology institute from theNetherlands, VSL. The comparison protocol, traveling standards and evaluation results wereprepared by the VSL.
Measuring Instrument
VSL uses a commercial instrument based on
the time base method. The sensor of the
stopwatch calibrator (Fig.2) is sensitive toradiation that is commonly emitted fromstopwatches. This radiation can be 32.768 kHz(internal oscillator), 32 Hz (LCD display) or
1 Hz (motor). The calibrator is calibrated byapplying a known frequency signal derived
from a reference frequency standard.

Fig. 2. Stopwatch calibration set-up at VSL

The transfer standards used in the comparison were an electronic stopwatch with LCD display and anelectronic wristwatch with LCD display.
The results of the comparison show that there is a good agreement between the two laboratories within
the combined relative uncertainty of 0.3 µs/s for a time interval of 1 day.
1

Jeff C. Gust, Robert M. Graham and Michael A. Lombardi, “Stopwatch and Timer Calibration (2009 edition),”NIST
Special Publication 960-12, 66 pages, January 2009

IFCS-EFTF5-PAB5-5

Analysis of the Sagnac Effect on the Accuracy of the Long Haul
Optical Fiber Time Transfer System
Yu Longqiang , Lu Lin, Wang Rong, Jing Jisong, Wu Chuanxin, Zhu Yong, Zhang Baofu
PLA University of Science and Technology, Nanjing, China
Email: nj_lulin@163.com
In recent years, time transfer on long-haul optic fiber is proposed to compare two geographicallyseparated clocks with high accuracy, on condition that the propagation time between two clocks isreciprocal or the unequal propagation time can be accurately measured and compensated 145-2. In thispaper, to the best of our knowledge, the influence of Sagnac effect in time transferring system overoptical fiber is discovered and analyzed for the first time.
The Sagnac effect3 in optic fiber time transferring system can be illustrated as Fig1. A and B are
two points on the earth. The dashed line AB denotes the original optical fiber link between A and B.
Simultaneous propagation processes are separated into two sequential processes to explain thephenomena more clearly as following: In time t, an optical signal is sent out from the A and it arrives at
B in time t1. Then, the signal starts in the opposite direction from B to A and reaches A in time t2. So theactual bidirectional paths are A-B1 and B1-A2 instead of A-B since the optical fiber is moving with theearth rotation. It is evident that bidirectional propagation times between two stations are unequal due to
Sagnac effect, so calculation and compensation are needed tozachieve accurate synchronization.
Ω

B1

B
t

t1

A

A1

B2
t2

A2

Infinitesimal of the fiber link and Lorentz-Einsteintransformation are used to deduce the equation (1) which cancalculate the Sagnac induced time deviation. The curve LAB
denotes an arbitrary fiber link illustrated in Fig.1. q is azimuth
angular and  is polar angular in spherical coordinates through thefiber link. R is the mean radius of the earth, Ω is the earth angularvelocity and c is the speed of light in vacuum.
(1)
T   (Rsinφ)2 Ω / c 2dθ
L AB

Table.1 shows Sagnac time deviations calculated by
Fig.1 Actual propagation paths of opticalequation(1) when time is transferred from Prague to other four
signals
Sagnac effectOffset(ns)City considering
Distance(km)Europe cities with different directions through spherical
London1024.1-3.2903circumference fiber links. It is showed that the Sagnac deviation
may reach 10-9s when the transfer distance is longer thanRome1189.3-0.6357
hundreds of kilometers and it is also decided by practical route of
Moscow
1667.34.7355the fiber links. So accurate time compensation or calibration
concerning Sagnac effect should be committed for the purpose of
Stockholm 1054.3
0.6856reaching sub-nanosecond accuracy in long-haul optical fiber time
Table.1 Time deviation from Prague to othertransferring system.
cities due to Sagnac effect1

S. -C. Ebenhag, et al.. “Time transfer over a 560km fiber link ”. Proc. 22nd EFTF， p.2325, 2008.
V. Smotalacha et al.. “Time transfer in optical network ”, 42nd PTTI Meeting, p.427436, 2010.
3
R. Wang et al.. “Modified sagnac experiment for measuring travel-time difference between counter-propagating light beams
in a uniformly moving fiber”. Physcs Letters A, vol .312(2),p.710, 2003.
2

IFCS-EFTF5-PAB5-6

Interlaboratory Comparisons for Frequency Calibration:
A First Two-Year Campaign in Italy
Franco Cordara1, Diego Orgiazzi1, Valerio Pettiti2
12

Calibration Laboratories Department, ACCREDIA, Torino, Italy
Optics Division, Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
Email: diego.orgiazzi@tiscali.it

In 2011 and 2012 the Calibration Laboratories Department of ACCREDIA, the Italian Accreditation
Body, together with the Time and Frequency Laboratory of the Optics Division of INRIM, the Italian
NMI, organized two Interlaboratory Comparisons (ILC) for frequency calibration. The ILCs weredirected towards most of the Italian Accredited Calibration Laboratories (ACLs) aiming toexperimentally assess their metrological capabilities, as requested by ACCREDIA rules and according
to the ISO/IEC 17025:2005146. More than 85% of all the Italian ACLs for frequency calibration wereinvolved in the two ILCs - 8 in 2011, 10 in 2012 - which represents the first successful national
campaign in this field and maybe the first in Europe.
Both ILCs implemented a multilateral scheme having INRIM as the pilot laboratory and fulfilled the EA
requirements147. A set of instruments, preliminarily calibrated by the pilot laboratory, was circulated
among the ACLs. Each ACL hosted the instruments for one week while performing all themeasurements requested by the calibration protocol, before sending them to the next ACL. During eachcirculation, lasting from 5 to 6 months, the instruments were sent back once to INRIM for anintermediate calibration. A closure calibration was performed by the pilot laboratory at the end of eachcampaign in order to assess the consistency of the instruments performances in terms of stability andrepeatability.
The set of travelling instruments included a GPS Disciplined Oscillator (GPSDO) with a 10 MHz output
frequency used as reference standard for the ILC. A signal splitter allowed for connecting the GPSDO to
the same antenna already used in the ACL for its local GPSDO-based frequency reference. Moreover, anetbook was used to collect relevant internal data for remote monitoring of the travelling standard. In the2011 campaign, a low frequency function generator up to 15 MHz and a high frequency synthesizer up
to 3 GHz – both externally referenced by the travelling GPSDO - were used to generate the signals to bemeasured by the ACLs. In the 2012 campaign, the two generators were replaced with the internal
synthesizer of the GPSDO providing signals in the 1 Hz to 20 MHz range. Every ACL was asked toestimate the normalized frequency deviation of the 10 MHz provided by the travelling GPSDO versus
the frequency standard of the laboratory, applying its accredited calibration procedures. Both direct
frequency and time interval measurements were performed. Some decadic frequency values were alsomeasured. The calibration measurement capabilities at 10 MHz of the ACLs ranged from 10-9 to 10-12.
The paper will report all technical and logistic details of these ILCs (e.g., specification of travelling
instruments, measurements requested by the protocol, problems faced and lessons learnt), together withan evaluation of the normalized errors En. An overall critical assessment of the whole experiment will bealso provided and suggestions on possible improvements for future exercises will be discussed.

146

ISO/IEC 17025:2005 “General requirements for the competence of testing and calibration laboratories”

147

EA-2/14 M:2008 “Procedure for Regional Calibration ILCs in Support of the EA MLA”

IFCS-EFTF5-PAB5-7

Dual-Mixer Time-Difference Measurement system using Discrete
Fourier Transformation
Shinya Yanagimachi, Akifumi Takamizawa, Takehiko Tanabe, Ken Hagimoto, Takeshi Ikegami
National Metrology Institute of Japan (NMIJ), AIST, Tsukuba, Ibaraki 305-8563, Japan
Email: s.yanagimachi@aist.go.jp
Precise oscillator have been contributing to the development of modern science and technology, such as
the establishment of high-speed communications, navigation systems, and fundamental physics. Atomic
clocks play an important role in the reliable implementation of time and frequency standards. The DualMixer Time-Difference(DMTD) is the most appropriate way to measure the time difference between
precise oscillators with a typical standard reference signals of 5, 10, and 100MHz.148,2
For the past decade, owing to the development of digital signal processing(DSP), it is proposed that lowspeed analog-to digital converters(ADCs) are employed to deal with the beat signals instead of the timeinterval counter(TIC)3. This technique has an advantage that the measurement system has fewer
components than the conventional DMTD, as there is no need for Sinusoidal-pulsed converters(SPCs)
and zero cross detectors(ZCDs) in the TIC. Recently, for the DMTD using low-speed ADCs, we
proposed the usage of discrete Fourier transformation (DFT) as a DSP technique (Fig.1), 4 and clarified
the condition where the truncation error affect the accuracy to determine time difference and frequency
difference between two oscillators. The truncation error occurs because of the disagreement between thereal signals and suppositional signals based on the DFT.
In the conference, we will discuss the truncation error limiting the accuracy to determine the clockparameters, the realization of the measurement system(Fig.2), and the extensibility for multichannel
DMTD system.
beat signal
Input signals
DBM

IA

ADC
phase lock

Processing
unit
Common oscillator

IB

ADC

Fig. 47: Configuration of DMTD using DFT.
Contrast to a conventional DMTD, SPCs and TICs
Fig. 2: System noise floor expressed in terms ofis not required Instead, an ADC and a processing
Allan deviation as a function of the averaging time
unit for the DFT are used.
with the carrier frequency of the oscillator 10 MHz.

148
2

D. W. Allan, and Herman Daams: Proc. 29th Annual Frequency Control Symp., 1975, p. 404.

S. Stein, D. Glaze, J. Levine, J. Gray, D. Hilliard, D. Howe, and A. Erb: IEEE Trans. Instrum. Meas. 32 (1983) 227.

3

M. Uchino, and K. Mochizuki: Electron. Commun. Jpn. 87 (2004) 21.

4

S. Yanagimachi, K. Hagimoto, and T. Ikegami: JJAP, 52(2013) to be published.

IFCS-EFTF5-PAB5-8

Frequency reference transfer via optical fiber based on RF
photonic phase shifter
Jianguo Shen, Guiling Wu, Lingdong Wang, Weiwen Zou, Jianping Chen
State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong
University, Shanghai 200240, China
Email: wuguiling@sjtu.edu.cn
Frequency reference transfer via optical fiber is considered to be a promising method and has attracted
an intensive research149. In this paper, a novel scheme of optical fiber frequency transfer, where a linear
and stable RF photonic phase shifter (RFPPS) is designed and used as the transmitter and phasecompensator at the same time, is proposed and validated experimentally.
Fig.1 shows the schematic of the
proposed scheme. The RFPPS is
implemented by a dual parallel
Mach-Zehnder modulator and opticalfilter150. When a frequency reference
signal is applied to the RFPPS, two
subcarriers separated by thefrequency of the reference signal are
Fig. 1. The schematic of the propose frequency transfer system.
generated. Since the phase difference
FRM: Farlady rotation mirror.
of two subcarriers depends on thebias voltage with the relation:( ⁄ ) , the phase shift of the recovered reference signal on the PD can be tuning linearly and fastby the bias voltage of the modulator. Therefore, the phase noise induced by the optical fiber link can becancelled by simply controlling the bias
voltage of the modulator with the phase error
obtained by detecting the round trip phasefluctuation.
Figure 2 shows the measured timing drifts inopen and closed loop condition at receiver end
over 20km optical link. Compared to open
loop, the timing drift is suppressed from 130ps
to less than 1ps in closed loop.

Fig. 2. Timing drifts in open and closed loop

149

S. M. Foreman, K. W. Holma, K. W. Hudson, D. D. Jones, J. Ye, ”Remote transfer of ultrastable frequency references via
fiber networks” Rev. Sci. Instrum, vol.78, P. 021101, 2007.
150

J.G. Shen, G. L. Wu, W. W. Zuo, J. P. Chen, "A photonic RF phase shifter based on a dual-parallel Mach-Zehnder
modulator and an optical filter", Appl. Phys. Express, vol. 5, p. 072502, 2012.

IFCS-EFTF5-PAB5-9

Evaluation of a High Performance Continuous Time Interval
Analyzer for Measuring Phase Stability

Glenn Bideberg1, Sven-Christian Ebenhag1, Per Olof Hedekvist1, Freddy Ben-Zeev2
Sigura2
1

and RonSP Technical Research Institute of Sweden, Boras, Sweden
2
GuideTech, Mountain View, CA USA
Email: glenn.bideberg@sp.se

With an increased need for time interval precision in fiber frequency measurements within theframework of the National Metrology Institute for Time and Frequency in Sweden, an evaluation of acommercially available high performance “CTIA” Continuous Time Interval Analyzer on PCI card has
been made.
The device under test was GT668PXI CTIA “Continuous Time Interval Analyzer” from GuideTech Inc.
This is a device that currently is used for applications worldwide ranging from Satellite Tracking,
Semiconductor- and Optical Testing, to monitoring of atomic clocks. It has a specified 2ps resolution
which corresponds to the performance found in premium high-end Bench-Top Scopes.
The used methods for making clock frequency and phase measurements using a GT668PXI CTIA alongwith the Stable32 stability analysis software package will be presented together with the experimental
results. The measurements will be performed in a controlled laboratory environment. The device isevaluated by direct frequency measurement using the device under test as a high-resolution CTIA, andby 1pps time interval measurements using a pair of dividers to produce reference and measurement
signals and measuring their time difference.
Based on the results, an analysis of the suitability for the fiber-based measurements is performed by SP,
in comparison to alternative techniques such as phase comparators.

IFCS-EFTF5-PAB5-10

OPTIME – time and frequency dissemination system based onfiber optical network – PIONIER
W. Adamowicz4, A. Binczewski5, W. Bogacki5, A. Czubla3, P. Dunst2, J. Igalson4, J. Kołodziej1, P. Krehlik1,
D. Lemański2, M. Lipiński1, J. Nawrocki2, P. Nogaś2, P. Ostapowicz5, T. Pawszak4, J. Pieczerak4, M.
Stroiński5, Ł. Śliwczyśki1, K. Turza5
1

AGH University of Science and Technology (AGH), Krakow, Poland
2
Astrogeodynamic Observatory (AOS), Borowiec, Poland
3
Central Office of Measures (GUM), Warsaw, Poland
4
Orange Poland (TPSA), Warsaw, Poland
5
Poznan Supercomputing and Networking Center (PSNC), Poznan, Poland
Email: mlipinsk@agh.edu.pl, nawrocki@cbk.poznan.pl, a.czubla@gum.gov.pl,
Janusz.Pieczerak@orange.com, wojbor@man.poznan.pl,
We describe the current stage and perspectives concerning using the optical network for time and frequency
dissemination in Poland. In the first part we summarize an over-a-year continuous operation of 420 km-longconnection between GUM in Warsaw and AOS in Borowiec near Poznan151. The link is based on the fiber
optic system for time and frequency dissemination, developed at AGH152,153. Herein, for the first time, we arereporting over a year comparison of UTC(PL) and UTC(AOS) atomic timescales with this system, and werefer it to the results of comparisons performed by GPS-based methods, and we also address some practicalaspects of maintaining time and frequency
dissemination over fiber optical network.
In the second part we describe the OPTIME project(national time and frequency distribution system)
which is based on the experience gained on theconnection between GUM and AOS using fibers
provided by PSNC (PIONIER) and TPSA, and on ourother experiments154. We focus on general architecture
created in OPTIME project.
In the last part we present the first phase ofdevelopment of OPTIME system with two referencelaboratories: GUM – Warsaw and AOS – Borowiec,
with local repositories in PSNC – Poznan and Torun,
Fig. 48: National time and frequency
and with the first end-users in FAMO – Torun.
distribution system – first phase.
Acknowledgement:
Project
OPTIME(no.
PBS1/A3/13/2012) is co-founded by The National Centre for Research and Development – Poland.
151

Ł. Śliwczyński, P. Krehlik, A. Czubla, Ł. Buczek and M. Lipiński, “Dissemination of time and RF frequency via
a stabilized fibre optic link over a distance of 420 km”, Metrologia 50, 133-145, 2013.
152

P. Krehlik, Ł. Śliwczyński, Ł. Buczek and M. Lipiński, “Fiber optic joint time and frequency transfer with active
stabilization of the propagation delay”, IEEE Trans. Instrum. Meas. vol. pp.61 2844–51, 2012.
153

Ł. Śliwczyński, P. Krehlik, Ł. Buczek, M. Lipiński, “Frequency transfer in electronically stabilized fiber optic link
exploiting bidirectional optical amplifiers”, IEEE Transaction on Instrumentation and Measurement, vol. 61, no. 9, pp. 25732580, 2012.
154

P. Krehlik, Ł. Śliwczyński, Ł. Buczek, M. Lipiński, “Multipoint dissemination of RF frequency in fiber optic link withstabilized propagation delay”, paper submitted to IEEE Trans. UFFC, 2013.

IFCS-EFTF5-PAB5-11

Interpolating time counter with a multi-edge coding
Ryszard Szplet, Dominik Sondej, Grzegorz Grzęda
Faculty of Electronics, Military University of Technology, Warsaw, Poland
Email: rszplet@wat.edu.pl
Precise integrated time-to-digital converters (TDC) are typically based on discrete delay lines built as
chains of buffers155. Due to technological spread and changes in ambient conditions the delays of buffers
involved are non-uniform. It manifests in different widths of quantization steps of TDC transfer function
and ultimately deteriorates the resolution and linearity of conversion. The ultra-wide steps, especiallyobserved in FPGA-based TDCs, may be reduced in the process of conversion by detecting not a single
but a multiple signal transitions in a delay line156. The latter is further called a multi-edge coding.
In this paper we present the design, operation and test results of an interpolating time counter
with a multi-edge coding principle applied in the second stage of interpolation. The counter isimplemented in an FPGA device Spartan-6 (Xilinx) and provides a 2.6 ps resolution, 8 ps precisionand 1 s measurement range. The development of such a high performance instrument needs to solve
several design problems. The main of them are an implementation of a pattern generator and eliminationof bubble errors. The aim of the pattern generator is to produce and launch a model square signal with acertain amount of edges and possibly minimal delays between them. We designed and tested two patterngenerators based respectively on look-up tables and on a carry chain. The former one is simpler for
implementation while the latter allows to control parameters of the model signal. This is importantfeature for the quality of T/D conversion that depends, among others, on the complexity of the model
signal. We tested three variants of TDC with coding of three rising, three falling and six alternatededges.
With the increase in resolution of precise TDC, some invalid bits in the output thermometer code
(bubble errors) may be observed. It happens due to many reasons, for example, signal jitter, device
mismatch or supply voltage noise. In the TDC based on the coding of a single edge this error can beeasily eliminated by the virtual rearranging of delay line outputs. However, if both, rising and falling,
signal edges are coded additional hardware solutions are needed. In the designed time counter the bubble
errors are eliminated with the use of a fast asynchronous encoder.
Tests of the time counter reveal also the look-ahead effect in the carry chains built in the FPGA device.
This effect may cause loss of monotonicity of TDC transfer function. To avoid it, the order of delay
cells is again virtually changed by a dedicated priority encoder.
The further research on this method includes the use of the multi-edge coding described here in the
recently developed independent time coding lines157 that should lead to higher resolution and precision
as well as to smaller chip area.

155

J. Kalisz, “Review of methods for time interval measurements with picosecond resolution”, Metrologia, vol. 41, pp. 35–
51, 2004
156

J. Wu, Z. Shi, “The l0-ps Wave Union TDC: Improving FPGA TDC Resolution Beyond Its Cell Delay”, IEEE Nuclear
Science Symp. Conf. Record, pp. 3440–3446, 2008
157

R. Szplet, Z. Jachna, P. Kwiatkowski, K. Rozyc, “A 2.9 ps equivalent resolution interpolating time counter based on
multiple independent coding lines”, Meas. Sci. Technol. 24 (2013) 035904 (15pp)

IFCS-EFTF5-PAB5-12

Managment and monitoring layer of optical network for time andfrequency transfer
W. Bogacki2, J. Kołodziej1, J.Stępień1, K. Turza2
1

2

AGH University of Science and Technology, Mickiewicza 30, 30-057 Krakow, Poland
Poznan Supercomputing and Networking Center, Noskowskiego 12/14, 61-704 Poznan, Poland
Email: jacek.kolodziej@agh.edu.pl

We describe requirements analysis and basic hardware solutions of optical network management andmonitoring layer addressed to precise time and frequency transfer. We present current stage and perspectivesof supervising time transfer fiber link. The work is based on experience coming from an over-a-year
continuous operation of 420 km-long connection between Central Office of Measures (GUM) in Warsaw,
and Astrogeodynamic Observatory (AOS) in Borowiec near Poznan. The link is based on the fiber optic
system for time and frequency dissemination, developed at AGH158,159,160. The proposed solution will be usedin OPTIME project.
Time Transfer Subsystem
CWDM

C1, C2

C1, C2

CWDM

EDFA

M2

EDFA NodeInternal
routerTerminal
Port

Mediaconveter

M1Mediaconveter

Managment Subsystem

M1
M2

Ethernet
Port

We present specific requirements for monitoring,calibration and management the transmission lines
to ensure high functionality, safety, and quality ofthe time and the frequency dissemination. The
whole system must deliver information forproviders, end-users, and equipment producers.
One part of the paper contains a description of theessential
elementsofthesystemandcommunication methods, which are based on thestandard protocols like SNMP or SSH.

The second part includes proposed hardware
solution of optic system for time and frequency
transfer with management subsystem which use
multiplex data and management signals between
devices (IN and OUT of Band). The block diagram in Fig. 1 shows typical node of the system. Control andstatus data coming from dedicated EDFA (Erbium Doped Fiber Amplifier) are formatted into Ethernet
packet and distributed according routing table by internal router to 2 media converters or local external
Ethernet port. The CWDM module combines two control link (with M1 and M2 wavelengths) with timetransfer carrier (C1 and C2 wavelengths) in one common fiber. In summary we present preliminary resultsof transmission in couple of network configuration scenarios, showing data flow of managements packets.
Fig. 49. Node of fiber optic system for time andfrequency transfer with management subsystem.

Acknowledgement: Project OPTIME (no. PBS1/A3/13/2012) is co-founded by The National Centre for
Research and Development – Poland.

158

P. Krehlik, Ł. Śliwczyński, Ł. Buczek and M. Lipiński, “Fiber optic joint time and frequency transfer with active
stabilization of the propagation delay”, IEEE Trans. Instrum. Meas. vol. pp.61 2844–51, 2012.
159

Ł Śliwczyński, P. Krehlik, A. Czubla, Ł. Buczek and M. Lipiński, “Dissemination of time and RF frequency via astabilized fibre optic link over a distance of 420 km”, Metrologia vol. 50, doi:10.1088/0026-1394/50/2/133, 2013.
160

Ł. Śliwczyński, J. Kołodziej, „ Bidirectional optical amplification in long-distance two-way fiber optic time and frequency
transfer systems”, IEEE Transactions on Instrumentation and Measurement, in press.

IFCS-EFTF5-PAB5-13

Precision Time-Transfer over Optical Fiber Using an
FPGA-based Time-Transfer Modem
Michael J. Wouters, Magnus T.L. Hsu
National Measurement Institute, Sydney, Australia
Email: Michael.Wouters@measurement.gov.au
Precise frequency transfer over optical fiber has been an active area of research for a number of years
and attention has recently turned to precise time-transfer. Time-transfer differs from frequency transfer
in that the propagation delay of the signal needs to be measured continuously. Five techniques have beenreported: using a digital pulse161; using time-transfer modems designed for two-way satellite timetransfer162; using data framing information that is present on communications network traffic163; using
RF-modulated lasers at two different optical frequencies164; and a refinement of the Precise Time
Protocol165.
The work reported here is a Field Programmable Gate Array (FPGA) based implementation of a timetransfer modem, using off-the-shelf hardware. The goal is to integrate the time-transfer modem with thedigital radio-frequency transfer technique that we have previously reported166. Eventually, the systemshould be implementable on relatively low-cost hardware.
The current version of the modem measures the signal delay via pseudo-random noise (PRN) ranging
using standard GPS PRN codes. One attractive feature of implementing the modem on an FPGA is thatdifferent codes and interpolation schemes can be easily tried, since only changes to software are
required.
The modem has been benchtop-tested by inserting fixed delays in the signal path. These tests indicate adelay measurement accuracy better than 100 ps, with the measurement limited by the calibration of the
fixed delays. Measured delays show stability at the 1 ps level over periods of a week.
We are presently working on testing the modem on a number of optical fiber links that we haveavailable, and will be reporting the results of these experiments at the conference.

161

Wang, et al., “Precise and Continuous Time and Frequency Synchronisation at the 5×10 -19 Accuracy Level”, Sci. Rep.,
vol. 2, Article 556, 2012.
162

Dirk Piester, et al., “Time transfer through optical fibers (TTTOF): first results of calibrated clock comparisons”, Proc.
41st PTTI, p. 89-99, 2009.
163
Sven-Christian Ebenhag, et al.,“Time Transfer between UTC(SP) and UTC(MIKE) Using Frame Detection in FiberOptical Communication Networks”, Proc. 43rd PTTI, p. 431-41, 2011.
164
Sven-Christian Ebenhag, et al., “Single way fiber based time transfer with active detection of time transfer variations”,
Proc. 42nd PTTI, p. 413-25, 2010.
165
Pedro Moreira, et al., “White Rabbit: Sub-Nanosecond Timing Distribution over Ethernet”, ISPCS, 2009.
166

M. T. L. Hsu, et al., “All-Digital Radio-Frequency Signal Distribution Via Optical Fibers”, IEEE Phot. Tech. Lett, vol.
24 , p. 1015-17, 2012.

IFCS-EFTF5-PAB5-14

Fiber-optic Time and Frequency Transfer based on RF Carrier
Phase and Pseudorandom Noise CodeWenke Yang1, Hang Gong1, Long Huang1, Xiangwei Zhu1, Guangfu Sun1
1

School of Electronic Science and Engineering, National University of Defense Technology, Changsha,
Hunan 410073, China

Email: ywk@nudt.edu.cn
Many literatures have been reported on stable frequency transfer via optical fibers (both in optical and
RF domains). As to time transfer over fibers,
self-madeframe detection in SDH or SONET network,
self-madeModem 1Modem 2timing code including 1PPS signal transferred Clock
E/O
E/O
Clock
TU-01
TU-02
1km
02
using two-way Dense Wavelength Division 01
Multiplexing (DWDM)and two-way time transfer
O/E
RU-01
RU-02
O/E
over fiber link based on commercial modems
Fig. 50: The two-way fiber-optic time andhave been reported.
1PPS

1PPS

10MHz

10MHz

1PPS

1PPS

10MHz

10MHz

frequency transfer system with self-made modems

In this paper, the experiment based on self-madeand 1km spooled-fiber
modems and off-the-shelf fiber-optic devices
aiming at achieving precise fiber-optic time and frequency transfer technique based on radio frequency(RF) carrier phase tracking and pseudorandom noise code correlation is demonstrated. It is different
from the previous work on time transfer over fibers, for that the RF carrier phase information and thepseudorandom noise code are both used through the fiber-optic link in the two-way mode. It works like
two-way satellite time and frequency transfer (TWSTFT), but the signal propagation path is replacedwith optical fiber and the up and down frequency converting process for satellite transmit is replaced by
the intensity modulation and the corresponding direct detect of the optical wave. The RF carriers
modulated by different pseudorandom noise codes are transmitted by the fiber-optic link with intensity
modulation and direct detect of 1550nm optical wave in two-way mode. At both ends, the one-way
delay including time difference of both end clocks
are measured by pseudorandom noise code
correlation and RF carrier tracking. With theassumption of two-way transfer symmetry, thetime difference of both end clocks can becalculated.
1E-10

Carrier Phase
Code

ADEV

1E-11

1E-12

1E-13

The two-way transfer asymmetry caused by thedifferent optical wavelengths for both directions,τ (s)which is the case in DWDM system, is avoided
by the Code Division Multiple Access (CDMA) Fig. 51: The measurement noise shown as ADEVwith carrier phase and code respectively
system here. The demonstration system is withthe 66MHz carrier and 1km spooled-fiber. The
experiment shows that the two-way fiber-optic time and frequency transfer system with self-mademodems and 1km spooled-fiber is of the measurement noise with Allan deviation (ADEV) of 3.2×1011 -1
τ with carrier phase information and 9.1×10-11τ-1 with pseudorandom noise code correlation.
1E-14

1

10

100

1000

IFCS-EFTF5-PAB5-15

Study on the Method of Measuring and Estimating the Time
Synchronization Accuracy under Constellations Autonomous
Operation based on the Ground Testing System
Ren Xiaoqian1,2,3, Qin weijin1,2,3, Wu Haitao1,2 Hua Yu1,2
1

2

National Time Service Center, China Academy of Sciences, Xi’an, Shannxi/China
Key Laboratory of Precision Navigation and Timing Technology, CAS, Xi’an, China
3
University of Chinese Academy of Sciences, Beijing, China
Email: renxq@ntsc.ac.cn

With the development of satellite navigation systems and navigation warfare concepts proposed, thecapability of autonomous survival and operation of the satellite navigation system has become an
important part of the research in the field. Making the inter-satellite link to achieve the autonomous
function of constellation is one of the primary means to improve the viability of the satellite navigation
system. The study of measuring and estimating constellations autonomous operation timesynchronization’s accuracy in condition of the satellite navigation system operate normally is so little.
This paper discusses the importance of testing and verification for diffident working mode, it provides
one kinds of method of measuring and estimating the time synchronization accuracy underconstellations autonomous operation based on the ground testing system. In the paper, it gives the basic
principle and the computational model, verifying and analysing the method by simulation data.

Tra
Bro nspond
sign
adc
al
ast
sig
nal

nal
sig
l
na
ond
sig
ns p
ast
Tra
dc
oa
Br

The method of measuring and estimating the timesynchronization accuracy under constellations
autonomous operation based on the ground testing
Satellite B
Satellite A
system is worked under the mode of transmitting
and receiving signal itself. It transmits signal to theall satellites on the visible range by the same carrier
frequency, and transmits to the same satellite groundstation by satellite transponder, and trigger satellite
local time to broadcast signal by the special carrier
Tx Rx
frequency (to make a difference from theclocktransponder signal). The ground station receive
SATRE
broadcast signal and transponder signal. It candetermine the deviation between the satellite time
counterand ground standard time by comparing the
Figure1 The figure of working principle
deviation between the receive broadcast signal andtransponder signal. Thereby, it can measure and estimate the time synchronization accuracy underconstellations autonomous operation. The figure of working principle is shown in figure 1.
This method provides technical support for building global satellite navigation system ’s inter-satellite
link.

IFCS-EFTF5-PAB5-16

Ultra-Short Term Clock Offset Prediction for Two-Way Satellite
Time Synchronization
Zhang Shengkang1,2, Zhang Li1,2, Yang Yujie1
1

2

Beijing Institute of Metrology and Measurement, Beijing, China
Science and Technology on Metrology and Calibration Laboratory, Beijing, China
Email: Zhangsk@126.com

Based on the principle of two way satellite time transfer, a time synchronization system with masterslave structures is established. In the system, slave sites compare their clocks time with the master clockby two way satellite time transfer system in turn. After a period of comparison, the time offset, fractionalfrequency offset or even fractional frequency drift of the slave clock are estimated with respect to themaster clock. Then, the time offsets between the two clocks are predicted in the next period of time,
when the two way link is switched to another slave site. The time offset prediction error of the slave
clock is a main error source in the synchronization system. Three offset prediction algorithms called
linear fitting prediction, quadratic polynomial prediction and grey system model prediction areinvestigated.
In order to evaluate the performance of the above-mentioned clock offset predicting algorithms, fourgroups TWSTT data are selected randomly, each of them is 40min length. The previous 10min data isused to estimate the fractional clock parameters, and to predicting the next 30min clock offset. The later
30min TWSTT data is used to validate the performance of the algorithms. Fig. 1 shows two groups ofthe predicting results of the three algorithms. Tab. 1 lists the quantitative analyzing the predicting
performance. The results show the linear fitting algorithm has an obvious good performance in ultra-

Fig. 52: Comparison of the predicting performance of the three algorithms

short term prediction than quadratic polynomial method, And it’s quite simple than grey system model
algorithm. The time synchronization system use the linear fitting algorithm for clock offset prediction inpractice and has a good practical effect.
Tab. 1 Predicting error of the three algorithms
Quadratic polynomial
Alg.
Seq.
Avg.
Std.
Max.
1
2.503
2.640
8.887
2
-1.804
1.790
6.099

Grey system Model
Avg.
Std.
Max.
0.147
0.209
0.833
-0.410
0.387
1.251

Avg.
0.144
-0.406

Linear fitting
Std.
Max.
0.207
0.826
0.384
1.242

IFCS-EFTF5-PAB5-17

A Measurement Method of the GEO Satellite
Local Oscillator Error
Jing Wenfang1,2,3, Lu Xiaochun1,2, Wang Danni1,2, Zhang Fuchen1,3
1. National Time Service Center，Chinese Academy Of Sciences，XiAn Lintong710600, China
2. Key Laboratory for Precise Navigation, Positioning and Timing of the Chinese Academy of Sciences,
Xi’an 710600, China;
3. Graduate University of the Chinese Academy of Sciences，Beijing100039, China)
Email: jingwenf@126.com
Abstract: The Two-Way Satellite Time and Frequency Transfer (TWSTFT) method has, in recent years,
been accredited as the most effective and high precision system. But as the frequency stabilities oftoday’s sophisticated atomic-level clocks improve, so must the stability of a Two-Way system’s methodof time and frequency transfer. Carrier-phase information holds the promise of improving the stabilities
of TWSTFT measurements, because of the great precision at which frequency transfers can be achieved.
Many years ago, some scientists try to use carrier-phase in TWSTFT, in the trial of time and frequency
transferring between USNO and NIST station, some excited results proved the theory and showed thepromise of carrier-phase measurement. But because of the poor stability of telecommunications GEO
satellite and some other factors, the result didn’t review in other trial station. Then no further researchreference was published.
Recently, COMPASS system of china has launched several GEO satellite with high quality local
oscillator, which brought some brighter shining light for the carrier-phase application in TWSTFT. And
a COMPASS GEO satellite has transponder as well as satellite direct transmitter. So, a method based on
direct transmitter signal to model the satellite local Oscillator and forecast its changing trend ispresented. Then, the satellite clock bias at each moment can be obtained. According to the bias, theTWSTFT transmitter baseband can pre-adjust the transmitter clock to relief the clock bias error toenhance the TWSTFT precision.
The purpose of this paper is to discuss this recent work, with emphasis on the Kalman forecast model tocalculate the satellite local Oscillator bias. And the method of making use of dual frequency to get thesatellite local Oscillator changing trend is introduced. The simulation and measurement trial is on thegoing, results will be revealed in the text.

IFCS-EFTF5-PAB5-18

Research on Calibration of TWSTFT Link by GPS
Zhiqiang Yang, Kun Liang, Qinghua Xu, Aimin Zhang
National Institute of Metrology, Beijing, China
Email: yangzq@nim.ac.cn
Two-way satellite time and frequency transfer (TWSTFT) is one of the most precise techniques of timeand frequency transfer between laboratories. At present, TWSTFT is performed operationally in at least
two laboratories in the United States, twelve in Europe, and seven in the Asia Pacific region. The
cooperation is organized by the CCTF Working Group on TWSTFT.
The NIM01 TWSTFT earth station was established in year 2008, and participate the Europe-Asia
TWSTFT link now. After October of year 2012, NIM has participated the UTC calculate by both GPS
and TWSTFT. But the TWSTFT system of NIM is not be calibrated, so the calibration of NIM
TWSTFT Link is extremely urgent.
We research on the calibration technique of NIM TWSTFT Link by GPS. The time and frequency
transfer GPS receiver and transfer link are calibrated. We did time and frequency transfer experiment
between PTB and NIM use both TWSTFT and GPS time transfer system, process the experiment data ofboth system and get the time difference of them, so the TWSTFT Link is calibrated by GPS at NIM. The
calibration result is shown in Fig 1, the time difference of TWSTFT and GPS is about 1648ns, thecalibration uncertainty is 5ns.

Fig. 53: Time difference of TWSTFT and GPS, the experiment laboratory is NIM and PTB, the period is from
MJD56143 to MJD56166

IFCS-EFTF5-PAB5-19

Precision Analysis of Non-continuous Two-way Satellite TimeComparison
Wei Pei 1,2,3, Yang Xu-hai1,2, Guo Ji1,2, Li Zhi-gang1,2, Qin Wei-jin1,2
1National Time Service Centre, Chinese Academy of Sciences, Xi’an, China
2
Key Laboratory of Precision Navigation and Timing Technology,
Chinese Academy of Sciences, Xi’an, China
3
University of Chinese Academy of Sciences, Beijing, China
Email: weipei@ntsc.ac.cn

As one of the high accuracy time comparison methods, Two-way Satellite Time and Frequency Transfer(TWSTFT) is one of the important methods for Bureau International des Poids et Mesures (BIPM) toorganize international comparison, calculation of the International Atomic Time (TAI) and Coordinated
Universal Time (UTC). Due to the interference of emitting device of TWSTFT to co-located devices ofVery Long Baseline Interferometry (VLBI) or International GNSS Service (IGS) and the limitation ofsatellite transponder resources, the comparison is not proceed continuously. Ten consecutive days ofdata from C-band TWSTFT Network of National Time Service Center (NTSC) was used for analyzing
the precision of non-continuous TWSTFT. The raw data of non-continuous TWSTFT was dealt withlinear interpolation method. Then the result was compared with the result of continuous TWSTFT which
was seen as the true value. Finally, the influence of interval time to the precision of non-continuous
TWSTFT was analyzed. The comparison shows that: when the interval time is less than 2.5 days, theRMS of the difference between non-continuous and continuous TWSTFT is better than 1ns; when theinterval time is 0.5 day, the RMS is better than 0.5ns.

IFCS-EFTF5-PAB5-20

The building algorithm of system timeof auto-navigation constellation
1

Qin Weijin1,2,3, Sun Baoqi1,2, Yang Xuhai 1,2 , Guo Ji1,2 , Wei Pei1,2,3
National Time Service Centre, Chinese Academy of Sciences, Xi’an, China
2
Key Laboratory of Precision Navigation and Timing Technology,
Chinese Academy of Sciences, Xi’an, China
3
University of Chinese Academy of Sciences, Beijing, China
Email: qwj@ntsc.ac.cn

The building algorithm of system time is one of the research focus of auto-navigation constellation. This
paper is on the basis of classic algos algorithm, which based on centralized processing mode of autotimekeeping constellation, gives a kind of building algorithm of system-time of which modified
determination weight and prediction clock velocity: the choose of determination of on-board clock ’s
weight and selection of clock velocity ’s prediction are determinated by the on-board clock quantity
which referring to the computation and the aim of building system time . Lacking of longly on-board
clock data, it can not be used the method of determination weight of ground clock, while velocitychange of on-board clock can reflect frequency change of on-board clock all the same, so it uses clock
velocity insteading of clock frequency for determinating weight; in the classic algos algorithm, theclock velocity of former one month as clock velocity prediction of this month, this algorithm uses two
kinds of method of predicting clock velocity: a. with the former two epochs each satellite of each day
predict many days’ velocity, b. with the former two epochs each satellite of first day predict many days’
velocity. Choosing the on-board clock of best hour-stability as the main clock, ccording to definedsample interval, getting all the available on-board clock error relative to the main clock. The system timeis built by the following modified algos algorithm, finally, we get all the on-board clock error of thissystem time. This paper gives the computation model of building of system time, and with 60 days dataof IGS precise clock error to test the algorithm(system time is IGST).
The result shows: comparing to the equal weighted algorithm, the algos weighted algorithm has betterstability. Adding prediction has a significant improvement on the system time’s stability. The stabilityof clock error of method a and method b both improves obviously on the raw clock error. The systemtime of method a is better than method b, 60 days later, the difference of autonomous system time
which relative to IGST(International GNSS Service Time), method a is about 30ns, method b is about
70ns. It can be used for the building algorithm of system time of auto-navigation constellation.

IFCS-EFTF5-PAB5-21

Research On Technology of Pseudo-range measurement based on CMMB
Changjiang Huang1,2,3, Yu Hua 1,2, Yonghui Hu1,2, Yu Xiang1,2,3,
1. National Time Service Center, the Chinese Academy of sciences, Xi’An , China
2. Key Laboratory of Precision Navigation and Timing Technology, NTSC,CAS, Xi’an , China
3. University of the Chinese Academy of Sciences, Beijing ,China

The technology of China Mobile Multimedia Broadcasting (CMMB), which has been the multimedia
broadcasting standard of small-size portable electronic equipments, has won favor of more and moreusers. Many research institutes and their staff in china are focusing on the technology of mobile location
based on CMMB signal. CMMB, which is an Orthogonal Frequency Division Multiplexing (OFDM)
modulation system, can improve largely the precision of location because of its favorable anti-multipath
performance.
In signal structure of CMMB，both same thoroughly synchronization signals inserted in every beachand the continual pilots in all OFDM symbols can be used to capture and track the received signal. In theprocess of Pseudo-range measurement, united symbol synchronization from rough symbol
synchronization in time field and accurate symbol synchronization in frequency field is executed at first,
then the fraction and integer part of frequency offset are respectively estimated and revised. At last, withtracking in real time of sampling frequency offset and rectifying of the synchronization sampling clock
frequency of VCXO, the frequency offset from Doppler effects is decreased effectively. After symbol
and frequency synchronization, one of both consecutive same synchronization signals is selected and isdemodulated by means of FFT algorithm. After getting the Pseudo-random sequence from thesynchronization signal, we can achieve the cross correlation between the pseudo-random sequence andlocal corresponding pseudo-random sequence in receiver. At the same time, we track accurately thepseudo-random sequence using code tracking loop and achieve the time difference and pseudo-range
between the station and the receiver once the cross correlation peak value appears.
In this paper, we present and analyze a technique for pseudo-range measurement in CMMB receiver.
The symbol synchronization, the rectification of carrier frequency offset and the pseudo-range
measurement are simulated based on the sampled datum. The simulation result shows that the error of
carrier frequency offset is less than 10-13 and the precision of pseudo-range measurement is less than 6
meters when the sampling rate is 60 MHz.

IFCS-EFTF5-PAB5-22

Satellite Clock Modelling and Multi-GNSS Solutions
Etienne Orliac1, Rolf Dach1, Kan Wang2, Markus Rothacher2, Urs Hugentobler3,
and Drazen Svehla4
12Astronomical Institute, University of Bern, Bern, Switzerland
Institute of Geodesy and Photogrammetry, Swiss Federal Institute of Technology, Zurich,
Switzerland
3
Institut für Astronomische und Physikalische Geodäsie, Technische Universität
München, Munich, Germany
4
European Space Operations Centre, European Space Agency, Darmstadt, Germany
Email: etienne.orliac@aiub.unibe.ch

In traditional GNSS processing, an independent set of clock parameters is estimated every processed
epoch. It represents a huge number of parameters which highly correlate with station height andtroposphere parameters. However, no use is made from the fact that the most stable clocks (on the
ground and in space) could be modeled, and in turn, help stabilizing the overall GNSS solution.
Based on data from the Multi-GNSS EXperiment (MGEX) from the International GNSS Service (IGS),
we first analyze the performances of the GPS Block IIF and Galileo IOV satellites from the clock timeseries as computed by CODE (Center for Orbit Determination in Europe) over carefully selected periods
where, among other criteria, IOV satellites had their H-Maser clock active. This CODE MGEX solution
bases on the rigorous combination of GPS, GLONASS, and Galileo data, hence gives the possibility toinvestigate the (receiver dependent) inter-system biases (ISB) between the different GNSS. A special
emphasis is put on the GPS-Galileo ISB and recommendations for operational processing are given.
Still using MGEX data, we investigate the impact of clock modelling and solar radiation pressure
models on the determination of orbits and clock parameters for the IOV satellites. Kinematic orbit
determination with stochastic clock modelling is also investigated for all GNSS satellites carrying highly
stable clocks and results are compared.
Finally, MGEX data from a regional network is used to investigate the impact of deterministic andstochastic satellite clock modelling on parameters with a high resolution in time, such as kinematiccoordinates or troposphere parameters. The various solutions based on deterministic and stochastic clock
modelling are compared to the traditional solution were clock parameters are estimated independently
every epoch.

IFCS-EFTF5-PAB5-23

Real-Time Remote Calibration (RTRC) System for Time and Frequency
LIANG Kun1, ZUO Fei2, PEI Chao2, ZHANG Side3
1

2

Division of Time and Frequency Metrology, National Institute of Metrology, Beijing, China
School of Electronics and Information Engineering, Beijing JiaoTong University, Beijing, China
3
Beijing Trust GPS Science&Technology Development Co., Ltd, Beijing, China
Email: liangk@nim.ac.cn

Abstract: The time and frequency transfer receiver NIMTFGNSS-11 has been developed since 2011.
Based on it, real-time and remote calibration by GNSS code based time and frequency transfer has beenstudied, and one new type of real-time remote calibration system named RTRC has been designed andimplemented. The users who should be authorized by the administrator of the system can use one
NIMTFGNSS-1 receiver to check and get real-time (16-minute interval) remote calibration of their timescales and frequency standards for time and frequency on the web by the internet. As well, the user
could check and get the calibration results using any longer period historical data. For the user who has
no any time scale or frequency standard and needs either or both of them which time or frequency
should be traced to UTC(NIM), National Time and Frequency Primary Standard of China, NIM canprovide one low-cost Rubidium clock as the accessory of the receiver that makes up one time scaledisciplined by UTC(NIM) in real time (UTC(NIM) Disciplined Oscillator, NIMDO) together with thereceiver. NIMDO has the legal and direct traceability to UTC(NIM); its time and frequency accuracy
has been improved thanks to the high level reference time scale and time scale algorithm; its longstability has been ameliorated due to the real-time and short latency steering to UTC(NIM). For theverification and demonstration of RTRC system, five receivers have been laid up at the two campuses of
NIM and hereinto two of them have the accessories of Rubidium clock. About 10 ns and 2e-13
calibration uncertainty separately for time and frequency could be acquired. Referenced to UTC(NIM),
we can acquired preliminarily that the time and frequency accuracy of NIMDO could separately bebetter than 10 ns and 1e-13 averaging one day, and the time and frequency stability averaging one day
could separately be better than 5 ns and 1e-13. Soon we would improve the steering algorithm and lay
up five NIMTFGNSS-1 receivers at four different cities (Shenyang, Guiyang, Shanghai, and Beijing) in
China to verify longer baseline effects. In the near future, using GNSS real-time or near real-time
precise ephemeris products, GNSS carrier phase time and frequency transfer will be studied and appliedin RTRC and NIMDO to improve their performances.
References:
1. LIANG Kun, ZHANG Aimin, GAO Xiaoxun,WANG Weibo, NING Dayu，ZHANG Side, “Studyand Development of a New GNSS Receiver for Time and Frequency Transfer,” Proc. of EFTF 2012,
pp. 529-536, 2012.

IFCS-EFTF5-PAB5-24

The Application of VRS in Common-View Based One-Way Timing
MethodXu Longxia1,2, Guo Meijun1,3, Li Xiaohui1,2, Zhang Huijun1,2, Liu Yinhua1,2
1

2

NTSC, CAS, Xi’an, China
Key Lab of Precision Navigation and Timing Technology, NTSC, Xi’an, China
3
University of Chinese Academy of Sciences, Beijing, China
Email: xulongxia@ntsc.ac.cn

The concept of Common-View based One-way Timing Method (CV-OWTM) is proposed by the author
in the IFCS conference last year167. This method provides users a way to acquire the standard time withthe accuracy of about 5ns by observing navigation satellites168. However, the CV-OWTM performs asame deficiency like the common view time transfer, that is, the timing accuracy decrease with theincrease of distance between users and the reference stations. In order to solve this problem, the Virtual
Reference Station (VRS) technique that used in RTK is improved and applied to CV-OWTM.
The VRS in CV-OWTM is different from that in RTK in several aspects. The improved VRS operates
on the pseudo-range observations. Therefore, it has a wider work range and isn’t sensitive to the
movement of user positions. Moreover, the VRS correction is calculated by users not by the dataprocessing center which simplifies the communication between user and the data processing center.
The right figure shows the principle of VRS. Based on
a reference stations network in China, this paper will
discuss the optimal virtual correction algorithm forusers. The number of reference stations that users
adopted and the weights of involved stations both are
key factors that determine the generation of VRS
correction. Based on the selected two different kindsof user positions, combinations of different number ofstations and two methods of determining weights areexperimented.
The research results indicate that the VRS technique
can supply a gap of CV-OWTM for sure. The optimal
number of reference stations for users’ application is
one or three. And the distance between the user andreference station decide the weight of timing
observation of this station. All in all, the applicationof VRS can guarantee CV-OWTM provides thetiming accuracy of 5ns.

GNSSsatellites

Ref station 1

Ref station 2
VRS

User

Ref station 3

Fig. 54: The principle of VRS. According to thepositions of reference station, the user selects dataof appropriate reference stations and computes thetiming data of a virtual station near the user. Thenthe timing data from the nonexistent station isapplied to correct the output of the user receiver. As
the timing data is relative to the standard time, theuser can obtain the standard time information
ultimately.

167

Xu L X, “A new timing method based on common-view”, 2012 IFCS Proceedings, p. 181-184, 2012.

168

Xu L X, “Study of a new one-way timing method”, Sci China: Phys Mech &Astron, vol. 55, p. 2476-2481, 2012.

IFCS-EFTF5-PAB5-25

Precise Point Positioning with integer ambiguities in the Atomium
softwareMari Carmen Martínez-Belda1, 2Pascale Defraigne
1

Applied Mathematics Department, University of Alicante, Spain
2
Royal Observatory of Belgium, Brussels, Belgium
Email: carmen.martinez@ua.es

The time-transfer technique based on Precise Point Positioning (PPP) has proved to be a very effective
technique allowing the comparison of atomic clocks with a precision of a hundred picoseconds.
However, one limitation for the accuracy of the solutions comes from the fact that the ambiguous
inherent term (integer number of cycles) of the carrier phases cannot, in a PPP approach, be solved as aninteger number; only float value (which includes remaining un-calibrated hardware satellite and receiverbiases) can be determined. Nevertheless, since 2007, several studies have demonstrated the possibility toresolve ambiguities at the un-differenced level169,170. The IGS analysis center CLS now distributes
satellite clock biases171 which allow to solve for integer ambiguities in a single-station PPP computation.
This paper will present the recent developments introduced in the Atomium software to produce aninteger ambiguity PPP solution, and the first results obtained for the UTC(k) comparisons.

169

D. Laurichesse and F. Mercier, « Integer ambiguity resolution on undifferenced GPS phase measurements and its
application to PPP », ION-GNSS 2007, Fort Worth, Texas.
170
171

P. Collins, « Isolating and estimating undifferenced GPS integer ambiguities », ION NTM 2008, San Diego, California.

S. Loyer, F. Perosanz, F. Mercier, H. Capdeville, and J.C. Marty, « Zero-difference GPS ambiguity resolution at CNESCLS IGS Analysis Center », J. Geod., vol. 86(11), p. 991-1003, 2012.

IFCS-EFTF5-PAB5-26

A Detection Algorithm of Frequency Jumps for GNSS Satellite
ClocksX.M. Huang1, H. Sha1, H. Gong1, X.W. Zhu1, G. Ou1
1

Satellite Navigation R&D Center, National Univ. of Defense Technology, Changsha 410073, China
Email: huangxinming_2007@163.com

As the frequency and time reference of space satellites, satellite clock has a direct influence on GNSS
service performance. Any anomaly of the atomic clock behavior on board the satellites causes errors foruser position. Therefore, it is necessary to detect clock anomaly. Frequency jumps are one of the mostcommon anomalies in atomic clocks of on-board satellites, which appear due to space radiation,
temperature change and other factors. In this paper, Original measurement data are pre-whetted byexponential filter, and real-time satellite clock frequency residuals are obtained by least squares
estimation, and a novel sum test statistic based on residuals is constructed. Optimal detector and energy
detector based on frequency residuals are proposed in order to evaluate performance of the new detector
constructed. Performance of the new algorithm is analyzed and verified by simulation. The results showthat the new algorithm has a perfect performance of detecting frequency jump. The detection algorithmof frequency jumps for satellite clocks proposed in this paper is helpful to GNSS satellite clockautonomous integrity monitoring.

IFCS-EFTF5-PAB5-27

Combination of T2L2 and GPS-CP data :Towards an improvement of Time Transfer Accuracy
Ph. Guillemot1, P. Exertier2, E. Samain2,
M. Laas-Bourez2, J. Delporte1
1
CNES –French Space Agency, Toulouse, France
2
OCA – Observatoire de la Côte d'Azur, Caussol, France
philippe.guillemot@cnes.fr

Abstract
The Time Transfer by Laser Link (T2L2) experiment, developed by both OCA and CNES, performs
ground to ground time transfer up to intercontinental distances in non common views. The principle isderived from laser telemetry technology with dedicated space equipment designed to record arrival timeof laser pulses at the satellite. Using laser pulses instead of radio frequency signals, T2L2 permits torealize some links between distant clocks with expected time stability of a few picoseconds andaccuracy better than 100 ps.
On the one hand, several T2L2 experiments demonstrated the capability of the system to perform timetransfer with an accuracy in the 100 ps range172. Nevertheless laser operations are weather dependentand do not allow continuous comparison of remote clocks. On the other hand GPS time transfer is aworldwide, all weather, fully operational system. GPS data processing has been widely improved since
the first common view / single satellite time transfer and GPS Carrier Phase techniques now allow
continuous comparison with an accuracy in the nanosecond range. However, carrier phase data areambiguous and several methods were developed in order to overcome this problem. Performance of
these methods173 are widely demonstrated for frequency transfer and with continuous data. But someambiguities remain when there are gaps in the data and for accurate time transfer.
This work investigates the possibility to combine GPS-CP time transfer using single-difference (andzero-difference) integer ambiguity resolution174 and T2L2 data in order to improve the resolution of theremaining GPS-CP ambiguities, in case of interruption in the data, and the accuracy of the time transfer.
First we introduce the method and then we present some first results for common view time transfer
between European stations.

172

E. Samain et al, “T2L2: Ground to Ground Time Transfer”, EFTF 2012, Goteborg, Sweden, 23-37 may 2012.

173

D. Laurichesse et al, “Integer Ambiguity Resolution on Undifferenced GPS Phase Measurements and Its Application to
PPP and Satellite Precise Orbit Determination”, Journal of the Institute Of Navigation, pp 135-149, Vol. 56 N° 2, 2009
174
J. Delporte et al., “GPS Carrier-Phase Time Transfer Using Single-Difference Integer Ambiguity Resolution”,
International Journal of Navigation and Observation, Volume 2008 (2008), Article ID 273785,
doi:10.1155/2008/273785

IFCS-EFTF5-PAB5-28

The STE-QUEST Mission: Objectives and Mission Design, Spacecraft, Science Payload and Time& Frequency Links
Hess MP, Hechenblaikner G
Astrium Space Transportation, Friedrichshafen, Germany
Email: Marc-Peter.Hess@astrium.eads.net
Space-Time-Explorer-Quantum Equivalence Principle Space Test (STE-QUEST) is an M-class mission
candidate for launch in 2022/2024 in the ESA Cosmic Vision programme. It was selected by theEuropean Space Agency for an assessment study until mid-2013, which started with an ESA-internal
assessment, followed by ongoing mission assessment studies performed by competitive industrial teams.
The principle aim of STE-QUEST is to study the cornerstones of Einstein's Equivalence Principle,
pushing the limits of measurement accuracy by several orders of magnitude compared to what iscurrently achievable in ground based experiments. On one hand experiments are performed to measure
the gravitational red-shift experienced by highly accurate atomic clocks in the gravitational fields ofearth or sun. On the other hand differential accelerations of atomic clouds are measured with an atominterferometer to test the universality of free fall and the Weak Equivalence Principle.
The spacecraft accommodate an atom interferometer as well as a highly accurate space atomic clock
based on the ACES PHARAO clock. Time and frequency links in the microwave and optical domaincompare the on-board clock to ground clocks, each equipped with microwave antennae and opticalterminals. The ground stations are distributed over three continents in Boulder, Torino, and Tokyo. Inorder to maximize the signal, i.e. the frequency difference between the two clocks, a highly ellipticalorbit with perigee altitude of 700 km and apogee altitude of approx. 50 000 km is chosen.
We report on preliminary results of the mission assessment under the lead of EADS Astrium. Somebasic features of the mission design are discussed and the design concepts of the spacecraft, science
payload and time and frequency links are briefly reviewed.

IFCS-EFTF5-PAB5-29

BDS Satellite Orbit Determination Based on Inter-satellite andSatellite-to-station Ranging
Donghui Wang, Shaowei Yong
Navigation R&D Center, School of Electronic Science and Engineering, National University of Defense
Technology, Changsha 410073, China
Email: wdhhawk@gmail.com
The ground stations of BDS are all distributed in China. The distribution is so concentrated that thevisible arcs of MEO satellites are only less than 30% and the orbit determination accuracy is restricted.
Inter-satellite ranging to increase useful observation data is a very effective method to improve orbit
determination accuracy.
In the paper, a new TDMA frame structure is proposed as inter-satellite ranging work mode. The
structure is shown in figure 1. It consists of 15 minutes master frames repeated over time. The masterframe consists of two frames, the first is ranging frame, the second is communication and dataprocessing frame. Ranging frame is divided into N TDMA slots of 9 seconds each. Each satellite isallocated one slot. In order to increase inter-satellite ranges, each slot is divided into 3 ranging units of 3
seconds each.
1.5

15min
frame1R
T
N

Next 15minframe2

1

frame1

slot1

slotN

RTN Error

0.5

9s
slot2

0

-0.5

unit1 unit2 unit3
3s

-1

-1.5

0

50

100

150

time (10 minutes)

Fig. 1. TDMA Frame structure

Fig. 2. Orbit determination result with 0.3m inter-satellite
ranging error, 15 minutes ranging interval and 12 inter-satellite
ranging links

Under the new inter-satellite work structure, some simulations are carried on with different number ofinter-satellite ranging links, different ranging interval and different ranging errors.
Simulation results show that when the system ranging error of satellite-to-state is 0.6m, and randomranging error is 0.3m, the 3D satellite orbit determination accuracy is 14.5m(RMS), and the URE of 2hours prediction is 1.0m if inter-satellite link is not available. After adding the inter-satellite link system,
the orbit determination accuracy is improved greatly. When the inter-satellite ranging errors are thesame as satellite-to-station ranging errors, and the ranging interval is 15 minutes, the largest
improvement of orbit determination accuracy is 68.0%, and when system error reduced to 0.3m, thelargest improvement of orbit determination accuracy is 73.2%, and when system error reduced to 0.1m,
the largest improvement of orbit determination accuracy is 76.1%. The satellite orbit determination
accuracy under different ranging intervals and link numbers are also given. An example result is shownin figure 2. From the simulation results, the optimized inter-satellite ranging mode can be summarized.

IFCS-EFTF Group 6 poster session 1
Forum Hall
Monday & Tuesday, July 22-23, 2013, 01:00 pm - 02:00 pm and 3:30 pm - 4:30 pm
Chair:

Sébastien BizeSYRTE-Observatoire de ParisIFCS-EFTF6-PAB6-1

Optically trapping of magnesium for a lattice basedfrequency standard
Klaus Zipfel1, André Kulosa1, Dominika Fim1, André Kulosa1,Steffen Rühmann1,
Wolfgang Ertmer1, Ernst Rasel1
1

Leibniz Universität Hannover, Institut für Quantenoptik, Hannover, Germany
Email: zipfel@iqo.uni-hannover.deState-of-the-art optical clocks with neutral atoms probe a narrow transition of atoms which are tightly
confined in an optical lattice at the “magic wavelength”175. A promising candidate for such a frequency
standard is bosonic 24Mg because of its low sensitivity to black body radiation (BBR) and simple
electronic structure.
With this contribution we present the setup of the optical traps and report on the latest results. For
magnesium, loading the optical lattice directly from a magneto optical trap (MOT) is not efficientbecause of density limitations, high temperatures in the milli-Kelvin regime and the lack of adequate
sub-Doppler-cooling methods. We therefore transfer our atoms via the 1S0 - 3P1 transition to the triplet
manifold where we operate a second MOT and introduce a loss channel to the 3P0 state. Operating both
MOTs and the transfer laser simultaneously creates a flux of 3P0 atoms which can be used tocontinuously load a dipole trap, acting as an energy filter for only the coldest atoms176. Since the light at
the predicted “magic wavelength” of 469 nm ionizes the atoms in the upper 3Dj states of the second
MOT, we first load a dipole trap at 1064 nm where we accumulate up to 105 atoms at 50 µK. With thesubsequent transfer to the optical lattice we end up with up to 10 4 atoms at about 10 µK which can beused for spectroscopy.

175
176

M. Takamoto et al., “An optical lattice clock”, Nature, vol. 435, p. 321-324, 2005.

M. Riedmann, “Beating the density limit by continuously loading a dipole trap from millikelvin-hot magnesium atoms”,
Phys. Rev. A, vol. 86, 2012.

IFCS-EFTF6-PAB6-2

Towards one single highly stable master laser for theinterrogation of SYRTE’s Sr and Hg optical lattice clocks
Predehl Katharina, Nicolodi Daniele, Eismann Ulrich, Le Targat Rodolphe, Lodewyck Jérôme, Shi
Chunyan, Tyumenev Rinat, Bize Sebastien, Le Coq YannLNE-SYRTE, Observatoire de Paris, CNRS, UPMC, 61 avenue de l’Observatoire, Paris, France
Email: katharina.predehl@obspm.fr
Optical atomic clocks have reached a level of performance that allows us to sensitively probe theconcepts of fundamental physics in table-top experiments. Moreover, it is widely accepted that opticalclocks will constitute a future reference for the SI time and frequency units due to their very highstability and accuracy177. For instance, neutral atom optical clocks have been proposed to have afundamental Quantum Projection Noise (QPN) residual instability below 10-17 after 1s of integration
time178. However, this level of performance is currently covered by frequency fluctuations of the clockinterrogation laser that are aliased directly onto the measured atomic line (optical Dick effect). Towards
QPN limited clock operation, large effort has been spent to optimize the widely employed laser systems
stabilized to high-finesse Fabry-Pérot etalons that can currently reach residual instabilities as low as afew 10-16 179. However, cavity length changes due to the thermal motion of the mirror atoms pose asevere limit to this performance.
At the Laboratoire National de métrologie et d'Essais - Système de Référence Temps Espace (LNE-SYRTE) we
pursue a different approach that has recently been demonstrated to potentially achieve tenfold higher
laser stabilities180 181. Using this technique, the frequency discriminator to stabilize the laser is generated
by spectrally burning transmission lines into the inhomogeneously broadened spectrum of rare-earth
ions doped into a crystal matrix. At cryogenic temperatures, these ions are well shielded within the hostand the transition is widely decoupled from thermo-mechanical noise. This allows for transmission linewidths of less than 1 kHz at short integration times and low residual frequency drifts.
Based on this spectral hole-burning technique we propose to develop a laser system with a fractional
short term stability of less than 10-16 and a residual drift of less than 10 mHz/s. This includes thesystematic exploration of different matrix structures and mounting geometries in order to achieve
optimized performance. This laser will serve as a master for the interrogation lasers of three different
optical clocks. In particular, this comprises two strontium optical clock systems at 430 THz (698 nm)
and one mercury optical clock system at 1.2 PHz (266 nm)182 183. The phase stability of the master at 258
THz (1160 nm) will be transferred to the different clock wavelengths by means of an optical
femtosecond frequency comb. Recent experiments conducted at LNE-SYRTE show that the frequency
conversion preserves the master's spectral purity. This also includes the fiber-based frequency
dissemination between the different laboratories.

177

P. Gill, F. Riehle, “On secondary representations of the Second”, Proc. of EFTF 2006, Braunschweig 2006.
M. Takamoto et al., “ An optical lattice clock” Nature 435, 321, 2005
179
T. Kessler et al., “A sub-40-mHz-linewidth laser based on a silicon single-crystal cavity”, Nat. Phot. 6, 687, 2012.
180
M.J. Thorpe et al., “Frequency-stabilization to 6×10-16 via spectral-hole burning”, Nat. Phot. 5, 688, 2011.
181
O-F Chen et al., “Spectrally Narrow, Long-Term Stable Optical Frequency Reference Based on a Eu3+:Y2SiO5 Crystal at
Cryogenic Temperature”, Phys. Rev. Lett. 107, 223202, 2011.
182
J. J. McFerran et al.,“Neutral atom frequency reference in the deep ultraviolet with a fractional uncertainty of 5.7×10 -15”,
Phys. Rev. Lett. 108, 183004, 2012.
183
R. Le Targat et al., “Accurate Optical Lattice Clock with 87Sr Atoms”, Phys. Rev. Lett. 97, 13081, 2006.
(see also arXiv:1301.6046)
178

IFCS-EFTF6-PAB6-3

Transportable Strontium optical lattice clock
Nicola Poli1, Soroosh Alighanbari2, Geoffrey Barwood3, Qun-Feng Chen2, Ingo Ernsting2, Patrick
Gill3, Alexander Nevsky2, Stephan Schiller2, Marco Schioppo1, Lyndsie Smith4,
Denis Sutyrin1,
1
5
6
Guglielmo M. Tino , Stephan Vogt and the SOC2 team1

Dipartimento di Fisica e Astronomia e LENS, Universita’ di Firenze, INFN sezione di Firenze, Via
Sansone, 1 - 50019 Sesto Fiorentino (FI)- Italy
2
Heinrich- Heine-Universität Düsseldorf, Germany3
National Physical Laboratory Teddington, the United Kingdom
4
University of Birmingham the United Kingdom
5
Physikalisch-Technische-Bundesanstalt,Germany
6
Leibniz Universität Hannover, German; Observatoire de Paris, France; University ofBirmingham,; TOPTICA Photonics AG, Germany; EADS Astrium
Friedrichshafen, Germany; Menlo Systems GmbH, Germany; Kayser Italia S.r.l.,Italy; Centre Suissed’Electronique et de Microtechnique SA, Switzerland; Kayser-Threde GmbH, Germany
University of Neuchatel; Istituto Nazionale di Ricerca Metrologica, Italy
Email: nicola.poli@unifi.it
We report on the status of the research project SOC2: “Towards Neutral-atom Space Optical Clocks”
funded by the EU 7th framework programme (grant agreement #263500) with the main aim ofdeveloping demonstrators of transportable lattice clocks with ~10 -17 relative frequency accuracy [1].
Novel design solutions allowed us to reduce size, weight and power consumption with respect totraditional apparatus for laser cooling [2,3]. At the same time a high degree of operation reliability has
been ensured by a modular architecture.
Recently the laser-cooling atomic source developed in Firenze [2] has been integrated with compact
subsystems developed by the consortium and the clock is now fully operational. Compact laser sources
developed by PTB and University of Hannover have been stabilized through compact frequency
stabilization system (FSS) developed by National Physical Laboratory and University of Düsseldorf.
First tests demonstrated continuous operation of theclock for more than 4 hours.
Results on high resolution spectroscopy of the 1S03
P0 clock transition on Sr isotopes will be reported
together with a systematic uncertainty budget.
Moreover, prospects for performing absolute
frequency measurements with Italian mw primaryreferences (ITCsF1 and ITCsF2) and Yb opticalfrequency reference through a 650 km-long opticalfiber link will be discussed [4].
References[1] S. Schiller et al. “Let’s embrace space”, volume
II, 45, 452-463 (2012). ISBN 978-92-79-22207-8

Fig. 55: Lattice spectroscopy on 1S0-3P0 transition
on bosonic 88Sr atoms with SOC2 apparatus.

[2] M. Schioppo, et al., Proceedings of EFTF 2010 ESA- ESTEC[3] M. Schioppo et al. Rev. Sci. Instrum. 83, 103101 (2012)[4] F. Levi et al. Proceedings of 2013 IEEE—UFFC joint symposia (2013)

IFCS-EFTF6-PAB6-4

Comparison of Sr optical lattice clocks
Chunyan Shi1, Ulrich Eismann1, M. Gurov1, Rodolphe Le Targat1, Jérôme Lodewyck1
1

LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France
Email: chunyan.shi@obspm.fr

We present a set of high resolution comparisons between two state-of-the-art optical latticeclocks using strontium atoms. With a statistical resolution of 2×10 -17, we measure a relative frequency
difference of 1.1×10-16 between the two apparatuses, in agreement with the combined accuracy budgetof 1.6×10-16. This comparison, beating the level of uncertainty that can be resolved by comparing
different optical clocks to microwave references, corroborates the established accuracy budget for
optical lattice clocks, and show that they are competitive for a possible redefinition of the second with
optical references1.
In addition, we present the ongoing development of a new vacuum system that will enablefurther improvement of the accuracy budget. A fine estimation of the temperature of the environment
surrounding the atoms will enable to decrease the contribution of the black body radiation shift in thelow 10-17 range without degrading the cycle time. Furthermore, the optical cavity used to generate theoptical lattice in which the atoms are trapped is doubly resonant for the lattice light and the 1S0 – 1P1
light (461 nm). With this cavity, the number of atoms in the fundamental clock state can be detected in anon destructive way by dispersive interaction between the atoms and the 461 nm light. Such a detection
yields an improved signal to noise ratio with respect to previous work 2. Here, we discuss heterodyne
detection strategies to reach the optimal detectivity, as well as progress in implementing these schemes.

1
2

R. Le Targat et al., “Experimenting an optical second with strontium lattice clocks”, arXiv:1301.6046 (2013)

J. Lodewyck et al, “Nondestructive measurement of the transition probability in a Sr optical lattice clock” Phys. Rev. A 79,
061401(R) (2009).

IFCS-EFTF6-PAB6-5

A transportable optical lattice clock using 171Yb

Gregor Mura, Charbel Abou Jaoudeh, Tobias Franzen, Axel Görlitz, Heiko Luckmann, Ingo Ernsting,Alexander Nevsky, Stephan Schiller and the SOC2 team2
1

Institut für Experimentalphysik, Heinrich- Heine-Universität Düsseldorf, Germany

2

Physikalisch-Technische-Bundesanstalt Braunschweig, Germany; Leibniz Universität Hannover,Germany; Observatoire de Paris, France; Universita’ di Firenze, Italy; Istituto Nazionale di Ricerca
Metrologica, Torino, Italy; National Physical Laboratory Teddington, United Kingdom; University ofBirmingham, United Kingdom; TOPTICA Photonics AG, Germany; EADS Astrium Friedrichshafen,
Germany; Menlo Systems GmbH, Germany; Kayser Italia S.r.l., Italy; Centre Suisse d’Electronique etde Microtechnique SA, Switzerland ; University of Neuchatel, Switzerland ;E-Mail: axel.goerlitz@uni-duesseldorf.de
Optical lattice clocks based on elements with two valence electrons are strong competitors in the quest
for next generation time and frequency standards. While promising results have already been obtainedon several stationary setups using Sr, Hg, Mg
and Yb, transportable clocks are desirable forboth performance evaluation and applications.
In the framework of the SOC2 project [1], weare developing a transportable Yb lattice clock
demonstrator. Our setup is based on compact
diode lasers (399 nm, 1156 nm followed bywaveguide SHG, 759 nm) and a fiber laser(1111 nm followed by waveguide SHG), andfeaturesanintra-vacuum
enhancement
resonator to allow the formation of a largevolume 1-dimensional optical lattice using
moderate laser power.
Here we present first results of spectroscopy ofFig. 56: Spectroscopy of the 1S0 → 3P0 clock transition
the 1𝑆0 → 3𝑃0 transition at 578 nm in 171Yb in an unpolarized sample of 171Yb trapped in an opticalconfined in a one-dimensional optical lattice. lattice in the presence of a magnetic bias field.
We have observed linewidths below 200 Hz
which were limited by saturation broadening. Currently the system is being improved towards
competitive clock operation as well as more compact and robust subsystems.
The research leading to these results has received funding from the European Union Seventh Framework
Programme (FP7/2007-2013) under grant agreement n. 263500.
References[1] www.soc2.eu; S. Schiller et al. “Towards Neutral-atom Space Optical Clocks (SOC2): Developmentof high-performance transportable and breadboard optical clocks and advanced subsystems” on “Let’s
embrace space, volume II” 45, 452-463 (2012). ISBN 978-92-79-22207-8

IFCS-EFTF6-PAB6-6

Improved set-up for the Ytterbium Optical Clock at INRiM
Marco Pizzocaro1,2, Luca Lorini1, Davide Calonico1, Giovanni A. Costanzo2, Filippo Levi1
1

Istituto Nazionale di Ricerca Metrologica, Torino, Italy
2
Politecnico di Torino, Torino, Italy
Email: m.pizzocaro@inrim.it

We present an upgraded setup for cooling and trapping of ytterbium atoms in the optical clock
experiment developed at Istituto Nazionale di Ricerca Metrologica (INRIM). The experiment aims tocool and trap ytterbium atoms in a two stage magneto-optical trap (MOT) (at 399 nm and 556 nm for the
first and second stage, respectively) and to probe the narrow-line clock transition at 578 nm in an opticallattice at the magic wavelength (759 nm).
We obtain blue light at 399 nm by second harmonic generation of a Ti:sapphire laser at 798 nm with alinewidth < 20 kHz. A lithium triborate (LBO) non-linear crystal in an enhancing cavity allows to obtainup to 0.6 W at 399 nm starting with 1.1 W of infrared light. To cope for the long term frequency drift,
the laser is locked to the atomic resonance by transverse spectroscopy on a ytterbium beam.
The green 556 nm radiation is obtained by second harmonic generation of an amplified 1112 nm Ybdoped fiber laser using a periodically-poled potassium titanyl-phosphate (PPKTP) crystal in single pass.
Up to 12 mW of 556 nm light has been obtained starting from 1.1 W of 1112 nm light. The laser isfrequency stabilized on a ultra-stable cavity.
The lattice laser is a Ti:sapphire laser with an output power of 3.2 W at 759 nm and has a linewidth <20 kHz. This source is able to provide large trap depths both for 1D and multidimensional latticeconfigurations.
A new physic package is designed, including the vacuum chamber, the MOT coils and the atomic
source. The new vacuum chamber is made in aluminum and it has indium-sealed viewports with highperformance anti-reflection coating for wide optical access and flexible lattice geometries. The target
vacuum pressure in the trapping region is better than 1x10-9 mbar, which allows the atom lifetime inlattice required by the optical clock operation. A high efficiency atomic oven source allows a highnumber of trappable atoms. Atoms can be slowed using a counter-propagating beam at 399 nm without adedicated Zeeman slower, exploiting the leaking field of the MOT coils.

IFCS-EFTF6-PAB6-7

An Improved Single-Ion End-Cap Trap for Optical Clocks
P.B.R. Nisbet-Jones, S.A. King, R.M. Godun, H.A. Klein, P.Gill
National Physical Laboratory (NPL), Teddington, UK
Email: peter.nisbet-jones@npl.co.uk
Recent advances in the field of single-ion frequency standards have resulted in optical atomic clocks
with systematic uncertainties in the 10-16- 10-18 range, beyond that of the best caesium fountains. At thislevel of precision, frequency shifts caused by the trap environment start to limit the achievable
performance of the standard.
One of the most significant shifts is the dc-Stark shift caused by blackbody emission from the trap
electrodes. As end-cap ion traps1 typically operate with RF electric fields in the range of 106 V/m,dielectric heating of the trap structure can cause a temperature rise of up to hundreds of degrees ifthermal performance is not considered in the design. In the case of Yb+ 2,3, for example, the mid-IR
radiation emitted will cause a frequency shift on the order of 10-17 per degree.
By building a trap from materials with high thermal conductivity, and by minimizing the intrinsic rfheating of the trap structure itself, this temperaturerise can be minimized. Combining good thermal
design of the trap structure with accurate in situ
measurements of the trap temperature, the black-bodyfrequency shift can be more accurately constrained.
One of the methods to reduce the blackbody shift isby mechanically polishing the electrodes, thus
reducing their emissivity. An added benefit of this isa reduction in the anomalous (phonon) heating of theion. With the 171Yb+ octupole transition in particular,
as it has an excited state decay rate on the order of
RF is applied to molybdenum electrodes via a heat sunk copper
nHz4, there is significant scope for reducing themount with large ceramic spacers to reduce dielectric heating.
Fourier limited linewidth if the phonon heating rate of
the trap can be reduced. This is predominantly achieved by using a large electrode spacing (0.75mm)
and utilizing the ~d-4 scaling of the anomalous heating rate.
This work is supported by the UK National Measurement System and the European Metrology Research
Programme (EMRP) and is performed alongside groups at NPL, PTB, CMI and MIKES. The EMRP is
jointly funded be the EMRP participating countries within EURAMET and the European Union.
,

1
3

C.A. Schrama, Optics. Coms., vol. 101, 32-36, 1993.
S.A. King, N. J. Phys., vol. 14, 013045, 2012

2
4

N. Huntemann, PRL, vol. 108, 090801, 2012.
M. Roberts, PRA, vol. 62, 020501, 2000

IFCS-EFTF6-PAB6-8

Progress report of an 27Al+ ion optical clock
Ke Deng, Zetian Xu, Wenhao Yuan, Jie Zhang, Zehuang Lu, and Jun Luo

MOE Key Laboratory of Fundamental Quantities Measurement, School of Physics,
Huazhong University of Science and Technology, Wuhan, P.R. China
Email: zehuanglu@mail.hust.edu.cn
The 1S0-3P0 transition of 27Al+ at 267.4 nm has long been recognized as an excellent optical clocktransition candidate. Here we give a progress report of our project to build an 27Al+ ion optical clock.
The first stage design goals for the 27Al+ ion optical clock are an inaccuracy level of 10-17 and stability of
10-16 in one second. The implementation of the 27Al+ ion optical clock will be through quantum logic
spectroscopy (QLS)184, as first proposed by NIST. A single 25Mg+ ion will be trapped together with asingle 27Al+ ion. The 25Mg+ ion acts as the logic ion and is used for sympathetic cooling and internal
state detection of the 27Al+ ion.
In the planned experiment, a 285 nm FHG laser is used for photo-ionization of Mg atoms, and a single
280 nm laser system will be used to cool and detect the 25Mg+ ion. The 280 nm laser is derived from an
1120 nm laser. Its SHG at 560 nm is locked to the transition of molecular I2. An electro-optic modulatoris placed between the SHG and FHG in the laser system to generate 9.2 GHz sidebands185. The FHG
stage of the laser is designed to be double resonant with bothcarrier and sidebands. One sideband of the 280 nm laser is usedfor Doppler cooling and detection, while the carrier of the 280
nm laser is further used for Raman sideband cooling of 25Mg+
ion. A linear ion trap is placed in the center of a UHV vacuum
chamber, which is made of titanium to reduce the magnetic field
influence. Fig. 1 shows the whole experimental setup. The linear
ion trap is also made of titanium, and coated with gold.
At the moment, both 285 nm laser and 280 nm laser have beensuccessfully frequency locked. The oscillator of 285 nm at 1140
nm was digitally locked to a high precision Toptica wavemeter. Fig. 57: Experimental setup
showing vacuum chamber andWith this laser, Mg atoms have been photo-ionized. Mg ionslasers for ion experiment. Inset
have been trapped and laser cooled with 280 nm laser, and shows pictures of crystallized Mg
crystallization of Mg ions has been observed. The inset of Fig. 1 ions.
shows pictures of crystallized Mg ions. One single Mg ion has
been trapped. Through micromotion compensation and trapping parameters optimization, thetemperature of this single trapped ion is lowered to around 8 mK, close to Doppler cooling limit. Further
experimental progress in Raman sideband cooling of a single Mg ion will be presented.

184

P. O. Schmidt, T. Rosenband, C. Langer, W. M. Itano, J. C. Bergquist, and D. J. Wineland, “Spectroscopy using quantum
logic,” Science, vol. 309, p. 749, 2005.
185

B. Hemmerling, F. Gebert, Y. Wan, D. Nigg, I. V. Sherstov, and P. O. Schmidt, “A single laser system for ground-statecooling of 25Mg+,” Appl. Phys. B, vol. 104, p. 583, 2011.

IFCS-EFTF6-PAB6-9

Progress Report on the Development of Ultra-stable Lasers for Al+
Optical Clocks
Yingxin Luo, Bing Ouyang, Xiaoyi Zeng, Jie Zhang, Zehuang Lu, and Jun Luo
MOE Key Laboratory of Fundamental Quantities Measurement, School of Physics,
Huazhong University of Science and Technology, Wuhan, P.R. China
Email: jie.zhang@mail.hust.edu.cn

The recent progress of ultra-narrow linewidth lasers used for Al+ optical frequency standards will bepresented. Two diode lasers are phase stabilized to ultra-stable ULE cavities, whose 4th harmonics will
be used as the de-shelving laser and the clock laser for Al+ clock transition respectively.
Al+ clock transition requires ultra-narrow linewidth laser as the clock laser with sub-hertz linewidth. To
develop this clock laser, a diode laser with wavelength of about 1070 nm is phase stabilized to two
independent cavities through two stages of Pound-Drever-Hall (PDH) locking. The output of the clock
laser is amplified, and then frequency quadrupled to generate the 4th harmonic ultraviolet output at 267.4
nm. To facilitate fast detection of the clocktransition, a de-shelving laser with linewidthof sub-100 Hz level at 267.0 nm is needed,thus another diode laser with wavelength of
1068 nm is phase stabilized to anothercavity (Fig. 1(a)) and then frequency
quadrupled to generate the ultraviolet
output. The ultra-stable cavities are made of
ULE materials with the zero-crossing
temperature of CTE (coefficient of thermal
expansion) near 25 °C, and are installed Fig. 58: Experimental schemes (a) for PDH stabilization of
inside vacuum chambers (Fig. 1(b)).
a diode laser with one of the ultra-stable ULE cavities; (b)Cavities with notched structures are the design of the cavity is optimized by FEA simulations,normally optimized for smallest vibration and is installed inside a vacuum chamber.
sensitivity through quasi-static Finite
Element Analysis (FEA) simulations186. Since quasi-static analysis does not consider the inertia anddamping effects, the calculated vibration sensitivity might not reflect the real results. Here we present
FEA dynamic analysis of the notched cavities steady state response under dynamically changing loads.
With the calculated results, and measured ground vibration spectral density curve, we can more
realistically predict the cavity length variations due to ground vibration. This dynamic analysis can also
be used for estimation of the acoustic noise influence on the cavity stability.
Latest results of the lasers, including static and dynamic FEA simulation results, characterization of thelocking systems performance, and laser linewidths and long-term stabilities measurement, will bepresented.

186

S. A. Webster, M. Oxborrow, and P. Gill, “Vibration insensitive optical cavity”, Phys. Rev. A, vol. 75, p. 011801, 2007.

IFCS-EFTF6-PAB6-10

An ultrastable optical oscillator for a magnesium lattice clock
Dominika Fim, André Kulosa, Steffen Rühmann, Klaus Zipfel, Wolfgang Ertmer, Ernst M. Rasel
Institut für Quantenoptik, Leibniz Universität Hannover, Hannover, Germany
Email: fim@iqo.uni-hannover.deSpectroscopy of the strictly forbidden 1S0 → 3P0 transitions in alkaline- earth elements are today
performed in the sub-Hertz regime. In order to observe this transition in lattice-trapped magnesium
atoms, a frequency doubled diode laser system, generating 458 nm, is stabilized to a horizontally
mounted high finesse resonator(F =600.000) at the fundamental wavelength of
916 nm. The resonator is made of ULE andfused silica mirrors. With this setup afractional instability of 5x10-16 in 1 s at 916
nm could be achieved. This is only factor of
two higher than the calculated thermal noise
floor of the resonator. We also studied thephase noise introduced by the SHG stage
contributing with an instability of 2x10-16
for 1s. We will give an overview of thissystem and will report on our results.
Fig. 59: Allan deviation of the second harmonic process
and the phase lock loop performance.

IFCS-EFTF6-PAB6-11

External Cavity Diode Laser at 420 nm Wavelength for Atomic
Spectroscopy
Xi Zeng1 and Dmitri L Boïko1
1

Centre Suisse d’Électronique et de Microtechnique, Jaquet-Droz 1, 2002 Neuchâtel, Switzerland
Email: xi.zeng@csem.ch, dmitri.boiko@csem.ch

Wavelength tunable diode lasers with narrow linewidths are vital for many applications in atomic
physics and spectroscopy. Specifications of these lasers are well established for probing alkali vapor
absorption lines in the near infrared (NIR) spectrum187. In the blue-violet wavelength range, there are a
few commercial models available, but they often lack information vital for atomic spectroscopy such as
relative intensity noise (RIN) and frequency noise spectra. Here, we report on our realization of an
external cavity diode laser (ECDL) suitable for interrogation of Rb vapor in the 52S1/2-62P3/2 (420.2 nm
wavelength) and 52S1/2-62P1/2 (421.5 nm) atomic lines as well as of Sr+ ions in the 2S1/2-2P1/2 coolingtransitions (421.6 nm).
The semiconductor gain chip used for the ECDL is a commercial InGaN/GaN Fabry-Perot laser withlasing wavelength around 420 nm. No specific provision for antireflection coating of the cleaved facet
was made, but we benefit from GaN-based lasers having naturally smaller facet reflectivity at ~17%than the 32-34% found in conventional GaAs-based lasers used for NIR spectroscopy. External cavity
feedback is provided by an optical grating with 1800 grooves per mm installed in Littrow configuration.
Challenges for single mode laser operation and uniform wavelength tuning originate from the modeclustering effect typical for GaN-based laser diodes. Nevertheless, our preliminary results demonstrateefficient mode filtering by the external cavity and large tuning range of the lasing wavelength. Figure1(a) shows the L-I curves of the laser diode without external feedback (lasing threshold ~40 mA) and in
ECDL configuration (lasing threshold ~31 mA). The ripples in the ECDL’s L-I curve are caused bymode hopping effects. The ECDL can achieve output power greater than 4.6 mW with injection currentof 110 mA. The wavelength tuning range is almost 7 nm while maintaining single lasing mode in the
optical spectrum as seen in Fig 1(b). The mode hop free tuning range is 57.7 GHz, which is more thansufficient for envisioned atomic spectroscopy applications. Figure 3(c) contains the ECDL’s preliminary
RIN measurement results (the RIN limited by photocurrent shot noise is 3×10-14 Hz-1). Measurements onfrequency noise and laser linewidth are ongoing.

0.4
3
0.3
ECDL
0.2

standalone
laser diode

2
1

0.1

0.0
0
30 32 34 36 38 40 42 44 46 48

current (mA)

1.0

relative intensity noise (1/Hz)

4

output power (mW)

0.5

-8

5

(a)

spectral density (a.u.)

output power (mW)

0.6

(b)

0.5

0.0
417

418

419

420

421

422

wavelength (nm)

423

424

10

(c)

spurious signals
from electronics

-9

10

-10

10

-11

10

-12

10

Detector shot-14
noise limit: 3x10

-13

10

-14

10

0

10

1

10

2

10

3

10

4

10

5

10

Fourier frequency (Hz)Fig. 1. (a) L-I curves of the laser diode without external feedback and in ECDL configuration. (b) Example lasing
wavelengths by the ECDL at 60 mA. (c) The ECDL’s relative intensity noise at 59 mA.

187

C. Affolderbach and G. Mileti, “A compact laser head with high-frequency stability for Rb atomic clocks and optical
instrumentation”, Review of Scientific Instruments, vol. 76, p. 073108-1 - 073108-5, 2005.

IFCS-EFTF6-PAB6-12

Stable frequency comparison of different optical clocks
Christian Grebing, Burghard Lipphardt, Stephan Falke, Nils Huntemann, Nathan Lemke, Thomas
Legero, Christian Hagemann, Uwe Sterr, Christian Tamm, Ekkehard Peik, Christian Lisdat, and Harald
Schnatz
Physikalisch-Technische Bundesanstalt, Braunschweig, Germany
Email: christian.grebing@ptb.de
Frequency standards based on ultra-narrow optical transitions of single ions or ensembles of atoms havereached a level of stability and reproducibility that surpassed those of primary clocks in the microwave
region. Currently at PTB, several types of optical clocks are investigated: ion clocks based on a single Yb+
and Al+ ion and an optical lattice clock based on neutral Sr atoms188,189. Since the individual clocks work at
different wavelengths an optical network based on frequency combs that connect different spectral regions isneeded for clock comparisons and frequency measurements
Commercially available frequency combs for metrology typically employ a common oscillator that feeds
multiple Er+-doped fiber amplifiers (EDFA) followed by short pieces of highly non-linear fibers to provide
high-power output at wavelengths according to customers’ needs. On the one hand this makes these combs ahandy and comfortable tool but on the other hand any noise generated in the EDFA branches will bias
measurements between different output ports of the comb system. We investigated this differential noise bymeasuring the frequency ratio of two cavity-stabilized
lasers in the visible and infrared spectral range with two
independent multi-port frequency comb systems190 (seeFig. 1). The Allan deviation shows an instability plateauof σy(τ) = 2∙10-16 between τ = 1...100 s, which is
attributed to environmental perturbations acting on theunstabilized fiber inside the EDFA paths. This instability
plateau can be further reduced by measuring andcompensating the differential noise. For longer
averaging times the instability averages down to σy(τ) <1∙10-18 for τ > 1∙104 s. The long-term instability is an Fig. 1: Measurement setup: The lines indicate
order of magnitude smaller than what is currently fiber links between the elements. The blue ones
achievable with the most advanced optical atomic are equipped with a fiber noise cancellation.
clocks.
This measurement is a first step for determining the ratio of PTB's 171Yb+ ion clock and 87Sr lattice clock
frequencies, which is currently under investigation, with minimum uncertainty contribution from thefrequency comb system.

188

N. Huntemann et al.,”High-accuracy optical clock based on the octupole transition in 171Yb+”, Phys. Rev. Lett., vol. 108, p.
090801, 2012
189
190

St. Falke et al.,”The 87Sr optical frequency standard at PTB”, Metrologia, vol. 48, p. 399 - 407, 2011

C. Hagemann et al.,”Providing 10-16 short-term stability of a 1.5-µm laser to optical clocks”, to appear in IEEE Instrum.
Meas., vol. 62 (preprint: arXiv:1208.1634)

IFCS-EFTF6-PAB6-13

Compact and Dual Ti: Sapphire Comb Lasers Pumped by Single
Fiber Laser
Tze-Wei Liu1, Chien-Ming Wu2, Shinn-Yan Lin3, Wang-Yau Cheng4
1

Department of Physics, National Taiwan University, Taipei, Taiwan
Institute of Photonics Technologies, National Tsing-Hua University, Hsinchu, Taiwan
3
National Standard Time and Frequency Laboratory, Telecommunication Laboratories, Chunghwa
Telecom, Taoyuan, Taiwan
4Department of Physics, National Central University, Chun-Li, Taiwan
2

Email: sylin@cht.com.tw
Ti:sapphire crystal is a commonly used gain medium both for continuous wave (CW) and mode-locked(ML) pulsed lasers in the near infrared (IR) region. Optical frequency combs are especially sensitive topower instability, because pump power fluctuations directly affect the repetition rate and the carrierenvelope phase. Improvements in IR fiber laser technology made possible to have sufficient opticalpump power in the visible region191 using second-harmonic generation in quasi-phase-matched
ferroelectric materials such as MgO-doped periodically poled stoichiometric lithium tantalate (PPMgO:SLT)192. Compared to the conventional diode pump solid-state laser pump sources, fiber laser
based pumps have the advantages of being morecompact, lower cost, and consuming less energy.
We demonstrated each femtosecond Ti:sapphirecomb laser pumped by 4.5W continuous-wave 532nm
light generated by frequency doubling a 1064nm
ytterbium fiber laser. The laser repetition rates were
set to be 1GHz and the average power of the plus isabout 700mW. Absolute mode frequency of laser was
directly monitored by a cesium two-photon stabilized
diode laser. In order to make the system small, wedevelop the hand size cesium two-photon stabilized
diode laser (HS-CTSDL)193 to be the frequency Fig. 60: After lock the comb laser, we measure thestandard of the absolute mode frequency. The beat note of one comb mode and cesium two-photon
instability of the HS-CTSDL frequency is about stabilized diode laser. Allan deviation of the beat
100Hz at 400s sampling time. A maximum frequency
frequency shows that the absolute frequency
discrepancy of 3.5kHz during 16 days shows the high instability was estimated as 5×10−12 at 10s sampling
reproducibility of the HS-CTSDL. We lock thetime.
repetition rate to the synthesizer, and lock the absolute frequency to the HS-CTDSL. The line width of
the repetition rate reduces to about 2Hz after lock. The standard deviation of the absolute frequency isabout 15.791kHz with 0.1 second get-time, and it will become about 6.072kHz with 1s sampling time.
The Allan deviation of the beat frequency shows that the absolute frequency instability was estimated as
5×10−12 at 10s sampling time.
191

G. K. Samanta, S. Chaitanya Kumar, and M. Ebrahim-Zadeh, Opt. Lett. 34, 1561 (2009).

192

H. Furuya, A. Morikawa, K. Mizuuchi, and K. Yamamoto, Jpn. J. Appl. Phys. Part 1 45, 6704 (2006)

193

Y-H Chen, T-W Liu, C-M Wu, C-C Lee, C-K Lee, and W-Y Cheng, Opt. Lett. 36, 76 (2011)

IFCS-EFTF6-PAB6-14

Optical Frequency Measurement Comparison Using Fiber Laser
Combs between CMS and NMIJ
Jin-Long Peng1, Ren-Huei Shu1, Tze-An Liu1, Hajime Inaba2, Kazumoto Hosaka2, Masami Yasuda2,
Daisuke Akamatsu2, Atsushi Onae2, and Feng-Lei Hong2
1

Center for Measurement Standards, Industrial Technology Research Institute, Hsinchu, Taiwan
2
National Metrology Institute of Japan, National Institute of Advanced Industrial Science andTechnology, Tsukuba, Japan
Email: jlpeng@itri.org.tw

An Er-fiber laser comb made by the Center for Measurement Standards (CMS), Taiwan was shipped to
the National Metrology Institute of Japan (NMIJ) to compare with the NMIJ fiber laser comb by
simultaneously measuring the frequency of a reference-cavity-stabilized Nd:YAG laser at 1064 nm. The
measured frequency difference is 32 mHz, which corresponds to a relative difference of 1.1×10-16.
Furthermore, method for determining the comb mode number using two combs with large difference ofrepetition rate is proposed.
Both the CMS and NMIJ fiber laser combs are home-made Er-doped ring fiber laser mode-locked by
nonlinear polarization rotation (NPR)194, 2. The laser head of the CMS fiber laser comb is only about an
A3 paper size with 7-mm thick, which is very compact and easy for transportation. The repetition rates
are 250 MHz and 87.6 MHz for the CMS and NMJ comb, respectively. The repetition and offset
frequencies of both combs are phase locked to the RF references synthesized from an H-maser linked to
the Coordinated Universal Time (UTC, NMIJ). The two combs are beating with the Nd:YAG laser,which has frequency instability of less than 110-14 at 1 s. The two beat signals and their divided-by-10
signals are measured with four counters simultaneously to check cycle-slip from the counters. If thecounting of the beat signal does not match with that from the 1/10 of the beat signal, cycle-slip has
happened and that data point is deleted. The
measured frequency differences are shown in Fig.
1. The averaged frequency difference is only 32
mHz, which is limited by the measurement time.
favg=31.5 mHz

600

An NMIJ fiber comb had also been shipped to the
National Metrology Institute, Australia to compare
the frequency measurement of an
iodinestabilized He-Ne laser at 633 nm in 2006. The
measured frequency difference was 38 mHz2. The
comparison results validate the measurement
capability of the CMS fiber laser comb.

Frequency (Hz)

400

200

0

-200

-400

-600

0

10

20

30
Time (s)

40

50

60x10

3

Fig. 61: Measured frequency differences between
the CMS and NMIJ fiber laser comb.

194

J.-L. Peng, T.-A Liu, and R.-H. Shu, “Self-referenced Er-fiber laser comb with 300 MHz comb spacing,” Proc. 2009 Joint
Meeting of the IEEE International Frequency Control Symp. and the EFTF Conf. p.344-346.
2

H. Inaba, Y. Nakajima, F.-L. Hong, K. Minoshima, J. Ishikawa, A. Onae, H. Matsumoto, M. Wouters, B. Warrington, and
N. Brown, “Frequency measurement capability of a fiber-based frequency comb at 633 nm,” IEEE Trans. Instru. Meas. vol.
58, p.1234-1240, 2009.

IFCS-EFTF6-PAB6-15

Experimental Setup of Cs Active Optical ClockZ. Xu, Y. Wang, D. Wang, X. Zhang, X. Xue, D. Pan, W. Zhuang, J. Chen
School of Electronics Engineering and Computer Science,
Peking University, Beijing 100871, China
Email: jbchen@pku.edu.cn
To push the linewidth of optical clock from Hz to mHz is a main topic for clock development195.
Active optical clocks2,3,4 theoretically have the potential of mHz linewidth, thus expected will provide
much better stability than that of passive optical clocks. In a three-level configuration5,6, the pumping
laser directly affects the frequency of clock transition. In order to greatly reduce the light shift of clocktransition caused by pumping laser, we are setting up an experiment to investigate active optical clock in
4-level configuration with Cesium atoms.
The melting temperatures of alkali atoms, like Cs
and Rb, are very low, and the laser diode forrelated wavelength of atomic transitions arecommercially available, thus Cs or Rb active
optical clock experiment with thermal cell ormagneto-optical trap is economic.
A homemade external-cavity diode laser at 455
nm is employed as the pumping laser. Saturated
absorption spectrum of cesium between 6S1/2(F=4) and 7P3/2 (F’=3,4,5) is observed. The
population inversion between 7S1/2 state and 6P3/2
Fig. 62: Experimental setup of cesium active opticalstate in a thermal cesium cell has been clock in four-level configuration. Mirror , Mirror
12experimentally established.
and Mirror3 are highly reflecting mirrors at
The experimental setup of cesium active optical 1529 nm. Mirror4 is coated with 1529 nm anticlock is shown in Fig. 1. The cavity is composed reflection and 455 nm high-reflection coating.
of a planar mirror (Mirror5) and a concave mirror Mirror5 is coated with 455 nm anti-reflection and
1469 nm high-reflection coating. Mirror6 is coated(Mirror6). Mirror5 is coated with 455 nm anti- with 455.5 nm high-reflection and the reflectivityofreflection and 1469 nm high-reflection coating. 1469 nm is 68.5%.
Mirror6 is coated with 455.5 nm high-reflection
and the reflectivity of 1469 nm is 68.5%. A 1529
nm external-cavity diode laser is used to calibrate the cavity. The 455 nm pumping laser is introduced
into the cavity to generate active optical clock laser output at 1469 nm. The experimental results will bereported.
195

D. Yu and J. Chen, “Optical Clock with Millihertz Linewidth Based on a Phase-Matching Effect”, Phys. Rev. Lett.., vol.
98, p. 050801, 2007.

2

J. Chen, “Active Optical clock,” Chinese Science Bulletin, vol. 54, p. 348, 2009.

3

Y. Wang, “Optical clocks based on stimulated emission radiation,” Chinese Science Bulletin, vol. 54, p.347, 2009.

4

D. Yu and J. Chen, “Laser theory with finite atom-field interacting time,” Phys. Rev. A, vol. 78, p. 013846, 2008.

5

D. Meiser et al., “Prospects for a millihertz-linewidth laser,” Phys. Rev. Lett., vol. 102, p. 163601, 2009.

6

J. Chen and X. Chen,“Optical lattice laser,” 2005 IEEE Freq. Contr. Symp., p. 608, 2005.

IFCS-EFTF6-PAB6-16

Dispersion Detection of Optical Clock Transition in Thermal
Atomic Beam
Xiaogang Zhang, Xiaobo Xue, Duo Pan, Wei Zhuang, Jingbiao Chen
School of Electronics Engineering and Computer Science,
Peking University, Beijing 100871, China
Email: jbchen@pku.edu.cn
In order to develop small optical clock for various transportable applications with better stability andaccuracy than that of commercial small Cs clock and H-maser clock, our group has proposed a small Ca
atomic beam clock scheme with electron-shelving detection196,2.
Its potential stability was
experimentally demonstrated recently3.
However, the residual ground state atom after the clock laser interrogation attributes very large
background of detected clock signal. One way to avoid this difficulty is to transfer most of ground state
atoms to 3P1 state in advance2 via adiabatic passage4. Here, we present dispersive detection of opticalclock transition in thermal Ca atomic beam, and this alternative detection method can effectively reducethe background light contribution due to the residual ground state atom after the clock laser interrogation
to clock signal.
The experimental setup of Ca atomic beam
optical clock with dispersive detection is shownin Fig. 1. We will discuss two experimental
schemes of dispersive detection. One is to apply
dispersive detection on 657 nm clock transitionof Ca atoms directly, but the signal amplitude islimited by atomic flux and low spontaneous
decay rate. The second scheme is to apply
dispersive detection on Ca atoms in the electron
shelving transition with a 423 nm laser afterconventional clock laser interrogation. The
experimental results will be reported.
Fig. 63: Experimental setup of dispersion detectionof optical clock transition in thermal Ca atomicbeam

1

Huang Kaikai, Zhang Jianwei, Yu Deshui, Chen Zhenhui, Zhuang Wei, Chen, Jingbiao, “Application of electron-shelving
detection via 423 nm transition in Calcium-beam optical frequency standard”, Chin. Phys. Lett., Vol. 23 p319,2006.
2
Kaikai Huang, Donghai Yang, Jingbiao Chen “Small compact Calcium-beam optical frequency standard in Peking
university and its new scheme”, Proc. of 20th EFTF, pp376-378, 2006, 27-30 March 2006, Braunschweig Germany.

John J. McFerran and Andre N. Luiten, "Fractional frequency instability in the 10 −14 range with a thermal beam opticalfrequency reference", JOSA B, Vol. 27, p. 277, 2010.
3

4

Xie Xiaopeng, Zhuang Wei, Chen Jingbiao, “Adiabatic passage based on the Calcium active optical clock”, Chin. Phys.
Lett., 27(7), 074202, (2010).

IFCS-EFTF6-PAB6-17

Testing Polish Optical Clock Calibration Procedures: Absolute
Frequency Measurement of Rubidium 5S-7S Two-Photon
Transitions
Michal Zawada1, Piotr Ablewski1, Wojciech Gawlik2, Rafal Gartman1, Piotr Maslowski1, Piotr
Morzynski1, Bartlomiej Nagorny1, Filip Ozimek3, Czeslaw Radzewicz3, Piotr Wcislo1, Marcin
Witkowski1,4, Roman Ciurylo11Institute of Physics, Nicolaus Copernicus University, Torun, Poland
2
Institute of Physics, Jagiellonian University, Krakow, Poland
3
Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
4
Institute of Physics, University of Opole, Opole, Poland
Email: zawada@fizyka.umk.pl
We report the absolute frequency measurements of rubidium 5S-7S two-photon transitions with an
optical frequency comb. The digital lock to the transition, the procedures of evaluating the accuracy
budget and measurements of the frequency with the optical frequency comb, which are prepared for thesystem of two optical lattice clocks with strontium atoms, are tested with much simpler setup. The
narrow 760-nm Rb 5S–7S two-photon transitions, insensitive to a magnetic field, are particularlyinteresting as a frequency standard. The similar line, the 778-nm Rb 5S–5D transition has been
recommended as the realization of the SI length unit meter197. As a result of this test, we obtained higher
accuracy of the transition measurement than any previously reported198 thanks to the very good longterm stability of our experimental setup.

197

Bureau International des Poids et Mesures (BIPM), in Report of the 86th Meeting of the Comité International desPoids et Mesures (CIPM), (BIPM, Sèvres, France, 1997)
198

Ming-Sheng Ko and Yi-Wei Liu, Opt. Lett., 29, 1799 (2004), A. Marian et al., Phys. Rev. Lett. 95, 023001 (2005),
K. Pandey et al., Opt. Lett., 33, 1675 (2008)

IFCS-EFTF6-PAB6-18

Compact Methane Based OFS with 3·10-15
short term stability

Gubin M., Kireev A., Lasarev V.*) Pnev A.*), Shelkovnikov A., Tyurikov D.
P.N. Lebedev Physical Institute, Moscow, Russia*)
N.E. Bauman Moscow State Technical University, Moscow, Russia
mgubin@okb.lpi.troitsk.ru
A compact optical frequency standard (OFS) with a short term stability at the level of 10-15 is needed for precise
time-frequency measurements, navigation etc. One of the important applications of such OFS is use as a source ofinterrogative signal for laser cooled ions and atoms in electromagnetic traps. In present work we developed a newgeneration of two-mode He-Ne/CH4 OFS stabilized over narrow saturated dispersion (SD) resonance at traditional
F22 line (ν3 vibrational-rotational band of methane, 3.39μm) [1]. This device will be used for repetition ratestabilization of a Er fiber femtosecond laser as in [2].
Essential improvements were introduced into regular design of this type of OFS with internal absorption cell. The
optical resonator was built as a zerodur monoblock unit without mechanical adjustments (except PZT elements);
optical losses of the mirrors and internal windows separating active and passive media were minimized, so that
total losses per round trip are estimated as 5-6 %. Special attention was paid to avoid parasitic back reflections
from any optical element in the resonator. As a result the device combines high passive stability with a goodquality quantum reference. Obvious advantage as compared to widely used lasers stabilized over high-Q cavities
is much slower frequency drift. Also the interrogative oscillator based on He-Ne/CH4 OFS does not requirecryogenic equipment as microwave generators based on sapphire whispering gallery resonators do.
Fig 1. Resonances of SD(lower trace)and SA (upper trace)
observed at themonoblock two-mode
He-Ne/CH4 OFS.

The parameters which determine Allan deviation of a frequency stabilized device are the beat frequency spectral
density fluctuations of a free-running He-Ne/CH4 OFS and a slope of the SD resonance at its center. At present
the free running monoblock He-Ne/CH4 OFS demonstrates spectral density of a beat frequency noise at the level~ 0.1 Hz/Hz1/2 (for typical laser output power ~ 0.1 mW) mainly determined by spontaneous emission (ShawlowTownes limit). The slope of the SD methane resonance at its center (the 1st derivative) is ~ 0.3 Hz/Hz (Fig.1,
lower trace).
It means that the frequency stability of a compact monoblock He-Ne/CH4 OFS can reach 3∙10-15 at 1s.
Direct comparison of two identical monoblock OFS is in progress and results will be discussed at the Conference.
________________________________
1

M.A. Gubin, E.D. Protsenko, "Laser frequency standards based on saturated-dispersion lines of methane", Quantum
Electron, 1997, 27 (12), 1048–1062.
2

M.A. Gubin, A.N. Kireev, A.V. Konyashchenko, P.G. Kryukov, A.S. Shelkovnikov, A.V. Tausenev, D.A. Tyurikov,«Femtosecond fiber laser based methane optical clock», Appl. Phys. B (2009) 95: 661–666.

IFCS-EFTF6-PAB6-19

IODINE STABILIZED IR LASER SOURCES
N. Chiodo1, N. Castagna1, M. Lours1, D. Holleville1, Y. Le Coq1, F. Du-Burck2, and O. Acef 1
1

LNE-SYRTE, Observatoire de Paris / CNRS-UMR 8630 / UPMC Paris 6, Paris, France
2
LPL/ CNRS-UMR 7538 / Univ. Paris 13 - Sorbonne Paris Cité, Villetaneuse, France
e-mail: ouali.acef@obspm.fr

Solid state lasers emitting in the IR, such as Nd: YAG or fiber lasers offer attracting possibilities
for development of compact and ultrastable setups, regarding to their low intrinsic phase noise, strong
output powers and robustness. On the other hand, iodine lines in the green range of the visible domain
exhibit high quality factor and strong signal-to-noise ratio yielding to confer to those lasers frequency
stability in the 10-14 range at 1s. Nowadays, high efficiency non linear crystals permit to link in simple
way the IR to visible range.
These couples of “IR laser/Iodine hyperfine line” are very promising for various terrestrial and/or
space applications such as transportable optical clock, ultrastable frequency references for spaceinterferometers, satellite laser links, long distance measurements, etc …
We report on iodine frequency stabilization of various IR laser sources on iodine hyperfine
transitions in the green range. Different harmonic generation processes based on several designs of
Periodically Poled Lithium Niobate non linear crystals (PPLN) are used to link the IR emission to thegreen region.
We have developed and tested various compact experimental setups using both multi-pass or intracavity short cells, in order to meet transportable/spatial requirements. Narrow hyperfine iodine lines
below 500 kHz width are detected in the 514 nm/532 nm range and used for the IR sources stabilization.

Record of the a10 hyperfine component of the
P 46 (44-0) line at λ ~ 514.5 nm(Time constant 1 ms)

The details of these developments and the results will be presented at the conference.
This work is supported by CNES, DGA-ANR (Contract 11-ASTR 001-01).

IFCS-EFTF Student Poster Competition
Forum Hall
Monday & Tuesday, July 22-23, 2013, 01:00 pm - 02:00 pm and 3:30 pm - 4:30 pm
Chair:

Leonhard Reindl
University of Freiburg

IFCS-EFTF-SPC-1

An Integrated SAW Sensor with Direct Write AntennaMark W. Gallagher1, William Smith2, Donald C. Malocha1
1Deparment of Electrical Engineering and Computer Science,
University of Central Florida, Orlando, FL 32816
2
MesoScribe Technologies Inc., St. James, New York 11780
Email: MGallagher@knights.ucf.edu

This paper presents a wafer-level integrated SAW sensor using conventional thin-film fabrication for the
SAW, and the direct write of a thicker dissimilar metal for the antenna. Previous proof-of-concept
results using thin antenna films demonstrated the feasibility of planar device integration, but had limited
interrogation range.199 For the first time, a direct write process is utilized to deposit the antenna
conductor onto the SAW substrate, providing ease of fabrication, optimal film thickness, and superior
adhesion. Shown in Figure 64, the automated thermal spray process selectively deposits conductive or
dielectric films onto a CAD defined area for rapid, conformal fabrication, allowing sensor integration ona range of surfaces. Results presented will show an increase in range, compared to previous work,through an improved low loss design.
Using the direct write process, shown in Figure 64, 15 μm thick copper is ‘written’ onto lithium niobate
without a mask. Thick antenna traces lower antenna resistive losses, because of increases in conductivity
and decreased skin depth effects. The traces adhere well to the 80 nm aluminum SAW transducer pads
that are patterned previously by a traditional photolithographic process. The process allows multiple
metal levels, trenching, and trimming, for optimum design and fabrication of research or a commercial
product. The updated design yields three devices on a 76 mm wafer and requires no mechanical bonds;
bond free devices are ideal for demanding environmental sensors.
Antenna gain and bandwidth trade-offs must be made to the integrated design to meet device size andsystem performance requirements. The design of a 915 MHz meandered dipole antenna with low
mismatch loss and maximized radiation efficiency over an 8% SAW fractional bandwidth isdemonstrated. Experimental performance results of antennas fabricated on standard FR4 and on-wafer
by electroplating or direct write process will be contrasted. Temperature sensors are fabricated on YZLiNbO3 and simultaneous operation, over temperature, in a multi-sensor system will be demonstrated
wirelessly at several meters. The integration of SAW and direct write technology offers a multitude ofopportunities for new sensor and communication system embodiments.

(a)

(b)

Figure 64: (a) The automated direct write robot printing to a part. (b) An example of a 915 MHz SAW sensor and direct write
dipole antenna integrated onto a 76 mm Y-cut lithium niobate wafer.

199

M. W. Gallagher, B. C. Santos and D. C. Malocha, "Wireless wideband SAW sensor - antenna design," in IEEE Int.
Frequency Control Symp., Newport Beach, CA, 2010, pp.291-296.

IFCS-EFTF-SPC-2

NANOMECHANICAL MASS SPECTROMETRY FOR THE CHARACTERIZATION OF
HIGH MASS NANOPARTICLES
E. Sage1, A. Brenac2, R. Morel2, C. Dupré1, C. Marcoux1, H. Blanc1, M. S. Hanay3, S. Kelber3, M.L.
Roukes3, E. Colinet1, L. Duraffourg1 and S. Hentz1
1

CEA, LETI, MINATEC campus, 17 rue des martyrs, 38054 GRENOBLE Cedex 9, France.
2
INAC/SP2M and Université Joseph Fourier, CEA Grenoble, 38054 Grenoble, France.
3
Kavli Nanoscience Institute and Departments of Physics, Applied Physics, and Bioengineering,
California Institute of Technology, MC 149-33, Pasadena, California 91125 USA.
Email: eric.sage@cea.fr
Nano Electro Mechanical Systems (NEMS)-based Mass Spectrometry (MS) holds great promise forpoint of care applications200 or air quality monitoring. Real-time, single protein MS has recently been
demonstrated with top-down silicon resonators201. These devices operate in a mostly unexplored mass
range where particles display a wide mass distribution and where there is no mass standard. A directcomparison of NEMS-MS and reference MS measurement (here conventional Time-Of-Flight (TOF)
MS) is therefore crucial and is presented for the first time in this paper. The NEMS device is fabricatedon a 200mm SOI wafer with VLSI process. It is a 160nm thick doubly clamped beam, electrostaticallyactuated, with heterodyne piezoresistive detection202. Its first two resonance frequencies are
simultaneously tracked with Phase Locked Loops.
The NEMS device is inserted in the deposition chamber of acustom sputtering-gas aggregation setup able to produce
nanometric metallic clusters with tunable deposition rate anddiameter203 (see Figure 1). First the NEMS experimental mass
sensitivity is calculated by varying the deposition rate,measured with a Quartz Crystal Microbalance (QCM). In asecond step, tantalum clusters were projected onto the surface
Figure 1: Schematic of the mass deposition setupof the NEMS with a flux rate allowing for individual particle
measurement. Figure 2 shows preliminary mass distributions obtained with both NEMS-MS and TOFMS: the distribution shape is reproduced with fidelity (widths at half maximum 352kDa and 408kDa
respectively) and the mean masses are very close. NEMS-MS displays a resolving power similar to
TOF-MS in this mass range, and even better athigher mass ranges. This demonstrates all thepotential of NEMS-MS in this mass range. The
mass
offset as well various mass distributions are underinvestigation.

Figure 2: TOF-MS and NEMS-MS mass spectra oftantalum clusters. (1 Da=1.66 × 10-27 kg). Inset:
frequency jumps induced by individual landing
events.
200

A. Boisen, Nature Nanotechnology, vol. 4, pp. 404-405, 2009.

201

M. S. Hanay et al, Nature Nanotechnology, vol. 7, pp. 602-608, 2012.

202

E. Mile et al, Nanotechnology, vol. 21, pp. 165504, 2010.

203

R. Morel et al, Eur. Phys. J. D, 24, pp. 287-290, 2003.

IFCS-EFTF-SPC-3

Micro-electro-mechanical resonant tilt sensor with 250 nanoradian resolution
Xudong Zou, Pradyumna Thiruvenkatanathan and Ashwin A. Seshia
Nanoscience Centre, Department of Engineering, University of Cambridge, United Kingdom
Email: xz280@cam.ac.uk
This paper reports on a high-resolution frequency-output MEMS tilt sensor based on resonant sensing
principles1. The tilt sensor measures orientation by sensing the component of gravitational acceleration
along a specified input axis (Fig. 1). The devices consist of a suspended proof mass connected to two
double-ended tuning fork (DETF) resonators at each end through a lever arrangement. When subjected
to a tilt with respect to the gravitational axis, the tuning forks respond through a shift in their resonant
frequency and the differential frequency shift can be then calibrated with respect to the tilt angle.
Prototype devices are fabricated in a foundry SOI-MEMS process and optical micrographs of the device
are shown in Fig.2. The microfabricated chips are mounted onto standard chip carriers and then vacuum
packaged using a custom process. A combination of design enhancements enables significantly higher
sensitivity for this device as compared to previously reported prototype sensors1.
The vacuum packaged sensor chip is co-integrated with oscillator circuits on a PCB and mounted on amanual tilt table. Figure 3 depicts the tilt test set-up and Fig. 4 shows the output frequency variation of
DETF_1 (see Fig. 1) observed in a 0o-90o tilt test. The tilt test results indicate that the new sensor
provides a relatively linear response in the range of ±20o with a scale factor of approximately 50.06
Hz/degree. Fig. 5 shows the results of a measurement on the output stability of the device as determinedby Modified Allan Deviation measurements. The resolution of the resonant tilt sensor is found to beapproximately 250 nano-radian for an integration time of 0.8 s, which is over an order of magnitude
better than previously reported results204. The impact of polarization voltage induced noise and drift isalso seen by comparing the two plots in Fig. 5.
s
re s
mp s
Co tres
S

in
g*s

M pro
F≈

DETF_1q
Freq.1
Increaseensil
Te essStrofθ

Freq.2
Decrease

DETF_2Z
Tilt Axis

Fig.1: Tilt sensor operation principle. Fig.2: Optical micrograph of sensor (inset: vacuum packaged device).
DC Power
SourceFrequency
CounterManual Tilt
Table
Alkaline
Battery for
Device Bias

MEM Chip with Frequency
Tracking
VacuumOscillator on
Package
PCB

Fig.3: Experimental set- up.
204

Fig.4: Output response versus tilt angle.

Fig.5: Measured output stability.

X.Zou, et al., "Micro-electro-mechanical resonant tilt sensor," Frequency Control Symposium (FCS), 2012 IEEE International, 21-24 May 2012.

IFCS-EFTF-SPC-4

Mapping Thermomechanical Vibrations and Mode Shapes
in High Frequency SiC-on-Insulator Nanoscale Resonators
Jaesung Lee1*, Zenghui Wang1, Mehran Mehregany1, Philip X.-L. Feng1*
1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
Email: jaesung.lee@case.edu, philip.feng@case.edu

We report on experimental demonstration of multi-mode radio-frequency nanomechanical disk resonators ina novel 500nm SiC-on-insulator (SiCOI) technology, and on measurements of directly mapping the modeshapes of the multiple resonances with high spatial resolution. By employing and engineering ultrasensitive
optical interferometric techniques, we measure the lowest possible levels of vibrations, i.e., the undriven
thermomechanical resonances arising from the intrinsic Brownian motions, in these SiCOI disk resonators.
Spatially mapping the resonant mode shapes of multi-mode nanomechanical resonators can greatly facilitate
understanding and harnessing these multiple modes for sensing and frequency control applications.
Our resonant devices (500nm-thick poly-SiC disks anchored on SiO2 center pedestals) feature a uniform
optical cavity (depth=500nm) with the underneath Si substrate. We use an optical interferometer with
fm/Hz1/2-level displacement sensitivity205,206, to transduce the thermomechanical motion of the device into
electrical signals. The ~1μm laser spot enables spatially mapping the different resonance modes.

S1/2(V/Hz1/2)
V

S1/2(V/Hz1/2)
V

S1/2(V/Hz1/2)
V

Figure 1 shows measured noise
0.8(a)spectraldensityof
five
0.6
mechanical resonance modes.
The peak amplitude of the mode
0.4
strongly depends on the laser
16.4
16.5
10.10 10.15
10.35 10.40
12.15 12.20
0.2
spot position (see insets). In the
0.8
center of the disk (position (a)),(b)
no measurable motion signal is0.6
observed. In the positions (b)0.4
and (c), we detect 5 and 4
resonance modes, respectively.
0.2
Measured resonance frequencies
0.8(c)and spatial maps of the mode
0.6
shapes (center row insets) agree
very well with COMSOL
0.4
simulation results (bottom row
0.2
insets).
We also observe
10
15
20interesting effects such as theFrequency (MHz)off-center position of the Fig. 1: Measured thermomechanical resonance spectra. Right insets: optical images
pedestal lifting the frequency showing the exact actual positions of the laser spot. Top insets: plots of resonances
degeneracy between the first two with fit (same y axis and scale as in main plots). Middle insets: spatial intensity map
modes
and
breaking
the for each mode. Bottom insets: COMSOL simulation of the mode shapes. Top right:
azimuthal symmetry in the mode SEM image (scale bar: 10µm).
shape of the third resonancemode, as well as electronically tuning the resonances, which we will report in detail in the full paper.

205
206

W. K. Hiebert, D. Vick, V. Sauer, M. R. Freeman, J. Micromech. Microeng. 20, 115038 (2010).
J. Lee, P. X.-L. Feng, Proc. IEEE Inter. Freq. Contr. Symp. (IFCS2012), DOI: 10.1109/FCS.2012.6243742.

IFCS-EFTF-SPC-5

Design of Ultra-Low-Power (2.5µW) 1GHz Low Phase Noise Pierce
Oscillator with Nanowire NEMS Resonator
Hamidreza Zamani1, Philip X.-L. Feng1
1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44016, USA
Email: hamidreza.zamani@case.edu.edu, philip.feng@case.edu

Laterally-vibrating nanowire (NW) resonators with high resonance frequencies fres and electrostatictransduction method are interesting for CMOS timing circuits. However, their motional resistance Rm isoften very high, much larger than their rivals FBARs with Rm of several ohms. Since Rm is also
proportional to the resonance frequency fres, design of high frequency oscillators are even more difficult.
In Pierce oscillators, the minimum MOS transconductance which makes oscillation feasible is207(parameters are identified in Fig. 1a). In this work, we propose and develop a
modified architecture using two small (bondwire) inductors (also connecting the nodes to DC bias
voltages) which reduce the effective motional resistance seen by the CMOS circuit. The analysis
includes novel analytical formulas for design of these modified Pierce-family oscillators working withresonators of initially high-motional resistance. As a proof of concept, we have provided Spectre
simulation results for a 1GHz oscillator with very low power consumption while having high voltage
amplitude at the output (drain of transistor M in Fig. 1a). The mechanical resonator assumed for thissimulation is a doubly-clamped Si NW with length, width, thickness and quality factor of respectively
419nm, 20nm, 80nm and 2000. Phase noise and spectral purity performance results are also provided.
The specifications in this work are compared to several recent related works. The specifications
reported in the Table for other works are measurement results.

Rm

Lm

Cg
C3

C′ 3

RBIAS
M

700mV

Lwirebond=1nH
C1C2
IBIAS=
100nA

067.319 dB

VDD=1.5 V

1.5
1.0

Phase Noise (dBc/Hz)

VDD=1.5VCm(c) -502.0

0.229 dBVpeak

Voltage Amplitude (V)Lwirebond=1nH

2V

0.5
0.0

-50

3.000

3.002
Time (s)-100-84 dBc/Hz-104 dBc/Hz

-100

-150

Phase Noise (dBc/Hz)

(b)

900mV

Peak Amplitude (dBV)

(a)

-100

-157 dBc/Hz
-150

-200

0

1

2

3
4
5
6
Frequency (GHz)78-200 2
10

1.020

1.025
Frequency (GHz)

1.030

3

4

5

6

10
10
10
10
Offset Frequency (z)7

10

Fig. 65: (a) Schematic of a 1GHz modified Pierce oscillator. (b) Spectral response of the oscillator harmonics compared to
the fundamental one. Inset: Oscillator output voltage in time domain (not connected to 50Ω load). (c) Phase noise simulation
results for offset frequencies around the major oscillation frequency (fosc=1.0256 GHz). Inset: Phase noise in a linear(absolute) frequency scale. The frequency resolution of sampling in the inset is lower, which causes difference in the phasenoise for frequencies very close to fosc.
This work[Zuo-CICC]208[Zuo-TUFFC]209[LavasaniISSCC]210

207

Rm
13.1MΩ
22Ω
25Ω
750Ω

fosc [GHz)
1.026
1.5
1.05
1.006

Pcon
2.5µW
6.9mW
3.5mW
1.9mW

Phase Noise [dBc/Hz]-84 (@1kHz), -104 (@10kHz), -157 (@1MHz)-85 (10kHz), -151 (@1MHz)-81 (@1kHz)-94 (@1kHz)

E. Vittoz, Low-Power Crystal and MEMS Oscillators: The Experience of Watch Developments, Springer 2010.
C. Zuo, J. Van der Spiegel, G. Piazza, “1.5-GHz CMOS…”, CICC2010, San Jose, CA, 2010.
209
C. Zuo, J. Van der Spiegel, G. Piazza, “1.05-GHz CMOS…”, IEEE Trans. UFFC, vol. 57, no. 1, p. 82-87, 2010.
210
H. H. M. Lavasani, W. Pan, B. Harrington, R. Abdolvand, and F. Ayazi, “A 76dBOhm, 1.7 GHz, 0.18um CMOS tunabletransimpedance amplifier…”, ISSCC 2010, San Francisco, CA, Jan. 2010, p. 318-320.
208

IFCS-EFTF-SPC-6

High spectral purity microwave and terahertz oscillator
Gwennaël Danion1, Goulc’hen Loas1, Ludovic Frein1, Cyril Hamel1, Anthony Carré1, Steve Bouhier1,
Marc Vallet1, Marc Brunel1, Antoine Rolland1, Mehdi Alouini1, François Bondu1, Alain Brillet2, JeanPierre Coulon2, Frédéric Cleva2, Mourad Merzougui2, Alexandre Beck3, Guillaume Ducournau3, JeanFrançois Lampin3, Mohamed Zaknoune3, Christophe Coinon3, Xavier Wallart3, Emilien Peytavit3,
Tahsin Akalin3, Grégoire Pillet4, Loïc Morvan4, Ghaya Baili4 and Jérôme Bourderionnet4
1
Departement Optique et Photonique, IPR, Université Rennes1 CNRS, Rennes, France
2
ARTEMIS, Observatoire de la côte d’Azur, Nice, France
3
Groupe Photonique/THz, IEMN, Université de Lille CNRS,Villeuneuve d’Ascq, France
4
Thales Research and Technology, Palaiseau, France
Email: gwennael.danion@univ-rennes1.fr
We present a microwave/THz oscillator project (2012-2014) excepted to show below -150 dB rad2/Hz
phase noise at an offset frequency of 10 kHz for a 30 GHz carrier frequency as well as 18 GHz, 100
GHz, 400 GHz, 1 THz. The microwave/THz signal is obtained by mixing two optical frequencies with aphotomixer.
A dual-axis two frequency cross polarization laser will be stabilized onto two resonances of one FabryPerot cavity. The two frequencies sense the same cavity length fluctuations so that the best possible
relative stability of the beat note is limited by the relative dimensional stability of the cavity. This cavity
spacer is made with an ultra low expansion ceramic (ULE) placed in vacuum. A 75% fraction of thebeam transmitted by the cavity is used to stabilize the amplitude of the laser, and a 25% fraction is sent
on a polarizer and a photomixer for optical to millimetre wave conversion. The AM/PM conversion,
especially the opto-thermal conversion in the cavity i.e. the absorbed power fluctuations, is negligible ata 1 Hz frequency offset by stabilization of the
optical carrier at the 8.10-9/Hz1/2 level.
This oscillator is based on a dual frequency laser
system whose beat note frequency is continuously
tunable from DC to 600 GHz. An
Erbium/Ytterbium solid-state two-axis dualfrequency laser system followed by amplifier
stage has been developed. Each polarization
frequencies is independently tunable by 1.7 GHz
Fig. 66: One microwave/THz oscillator
steps by tilting its etalon and continuously with anelectro-optic crystal. We have chosen two lithium
tantalate (LiTaO3) crystals; thermo-optic(600MHz/°C) and electro-optic (1.1MHz/V) effects enable to lock each frequency on the resonance of a
1.5 GHz free spectral range Fabry Perot cavity. Each polarization light beam is amplified by a fiber
system. Our system amplifier is composed of an erbium doped fiber amplifier (EDFA) and asemiconductor optical amplifier (SOA) per polarization axis. This amplifier system permits to deliver 18
dBm power, to stabilize the power fluctuations and to reduce the relative intensity noise by 20 dB,
especially the relaxation oscillation.

IFCS-EFTF-SPC-7

Inverse Relationship between OEO Q-factor and g-sensitivity
James P. Cahill1,2, Justin Pritchett1, Ryan Sorensen1, Morris Berman1, Olukayode Okusaga1, Weimin
Zhou1, Gary M. Carter2, Curtis R. Menyuk2
1

2

U.S. Army Research Laboratory, Adelphi, MD
University of Maryland: Baltimore County, Baltimore, MD
Email: james.p.cahill.ctr@us.army.mil

We present evidence that the vibration (g-) sensitivity of a fiber-based OEO decreases as the fiber length
wound to a single spool increases. This is the result of two effects. First, the magnitude of the vibrationinduced perturbation remains constant with increasing fiber length because of diminishing mechanicalcoupling between the outer layers of fiber and the spool. Second, the power spectral density (PSD) of
the phase noise induced by a constant magnitude perturbation decreases as the Q factor (i.e. fiber length)of the cavity increases. This is an oscillator filtering effect. We can exploit these effects to constructfiber-based OEOs with lower g-sensitivity.
A sinusoidal vibration induces a peak in the OEO phase noise at the vibration frequency with PSD
proportional to ( ⁄ ) , whereis the vibration-induced change in length of the fiber delay, and is
the length of the total fiber delay.xiv We use this sideband to characterize both the filter effect and themechanical coupling between fiber and spool. In order to maintain consistency we use identical spools inall tests.

Figure 1. PSD of the vibration-induced phase noise peak
as a function of the length of fiber exposed to vibration.
Total OEO delay is fixed.
Figure 2. PSD of the vibration-induced phase noise peak
as a function of total OEO fiber delay length. The entire
delay is exposed to vibration.

To demonstrate the diminished coupling between fiber and spool, we keep the total fiber delay of the
OEO at a constant length while exposing only a portion,, of the fiber delay to a sinusoidal vibration.
Fig. 1 plots the PSD of the vibrational sideband as a function of. Because we hold all relevant
parameters constant, the PSD of the vibrational sideband will be proportional to. Yet fig. 1 showsthat the PSD is independent of. Thus, the mechanical coupling between the fiber and spool has
effectively saturated, and is independent of the fiber length.
To demonstrate the oscillator filtering effect, we expose the entire fiber delay of the OEO to a sinusoidal
vibration. Fig. 2 plots the PSD of the vibration-induced sideband as a function of the total delay length,. The PSD of the sideband decreases approximately quadratically as fiber length increases. Thus, as the
OEO Q increases, the vibrational noise is effectively filtered out.

IFCS-EFTF-SPC-8

reportResonantly enhanced Fe3+ spin-spin
interaction
in cryogenic
Derivationof a System
Governing sapphire
Equation for

1

1
1
Oscillating
of1,WGMs
CoupledThrough
Jeremy Bourhill1, Karim Benmessai1, Maxim
GoryachevMagnitudes, Daniel Creedon
Warrick Farr
and Michael
1
a
Spin
Bath
Tobar
Maxim Goryachev...

1

EQuS Frequency and Quantum Control Metrology Laboratory, University of Western Australia, Perth,
I. S
C
WG M
Western Australia
YSTEM OFOUPLEDODESIn this study we consider a system of two coupled Whispering Gallery Modes of an Sapphire Dielectric resonator. We
consider two closest modes in the dielectric resonator of the microwave range of frequency. Each mode can be considered asa harmonic oscillator coupled to the environment. These modes are coupled through a bath of spins. So, the energy exchangemechanism implies energy storage in internal impurities of the crystal resonator and photon emission from impurities into two
photonic modes. This system is shown in Fig. I.

Email: jeremy.bourhill@uwa.edu.au

Spin Bath
WGM
WGM
We report the observation of a new behaviour
observed in sapphire crystal using paramagnetic
Fe3+ ions at cryogenic temperatures. When the
crystal is pumped at 12.04 GHz, exciting an
extremely high Q-factor whispering gallery
mode (WG mode) at the central frequency of a
Fe3+ spin transition, an additional signal isgenerated around 11.8 GHz, at the location of
Relaxation Bathanother WG mode. We show that this signal isexcited due to the broadened Fe3+ spin bath Figure 67: Model representing coupling between the two WG
mode resonances, ωm corresponding to the master or pumped
interacting with the 11.8 GHz mode; forming
an WGconsists
The whole system
the 12.04
following GHz
subsystems:
modeof atand ωs corresponding to the slave
master WG mode with a Hamiltonian H = ω a a, where a and a are creation and annihilation operators for a photon
effective three level system through population
WG mode at 11.8 GHz, via the Fe3+ spin bath.
in the mode;slave WG mode with a Hamiltonian H = ω b b, where b and b are creation and annihilation operators for a photon in
inversion. We also observe complex interaction
the mode, and ω > ω ;spin bath where spins of ω and ω energies exchange energy, where the difference ω − ω relaxes to a relaxation both;
between the pump at 12.04 GHz and the signal
relaxation bath representing external environment.
Thesystem works at three different time scales:
at 11.8 GHz when pumping is close to microwave
themode time scale τ ∼≈ 5 · 10seconds,
bath internal energy exchange process and spin-to-environment relaxation τ ∼ τ ∼ τ
τ , i.e. spins of twoformer’s bandwidth, resulting in Van der spinPolenergies ω and ω exchange quanta quick enough,WGM-spin bath energy exchange processes τ ∼ ττoscillations of the output power.
WGM own relaxation processes τ∼ττ , i.e. both WGM are high quality modes.
Figure 1.

General representation a spin-coupled WGM system

•

m

•

s

m

m

s

†

†

†

†

s

•

m

s

m

s

•

•

0

− 10

2π
ωs

•

1

m

2

e

0

s

•
•

m

rm

rs

s

e

m

In the following analysis we average over microwave time scale, neglect spin bath internal time scale, and consider WGM-spinbath coupling processes, considering WGM own relaxation time large enough.

Fe3+ ions are unintentionally substituted into the Figure 68: Energy level diagram of uncoupled spins (left)
crystal lattice during the manufacture process, and coupled spins (right). Spin coupling is due to3+theirand due to the crystal under investigation’s over simultaneous occupation, in frequency, of the Fe spinand close proximity in space. The resulting three levelannealing, they exist in populations much larger bath,system is made possible by the dissipation of energy
than normally observed. The spins excited by equivalent to the difference between the two signal
the pump can couple to other spins located frequencies.
nearby in the crystal with different frequency transitions (see Figure 1). The different energy transitions
exist as a result of the inhomogenously broadened spin resonance. The pump can decay through lower
energy transitions, and two in particular, the 11.8 GHz transitions, are enhanced by the fact that they arelocated at the nearest lower neighbour high-Q WG modes, and hence these signals are observable, andan effective three level system is established (see Figure 2).
maxim.goryachev@gmail.com

As pump detuning from ωm decreases, we first reach the masing threshold and hence we see the ωssignal switch on. As we tune more and approach our resonant frequency, more photons enter the systemat ωm until we reach a point where there is sufficient power at this frequency that the transitions of thecoupled spins becomes significant enough to cause oscillations in power of the two photonic modes. We
observe forced Van der Pol oscillations of the output power, as predicted by the model we derive from
Figure 1. The characteristics of these oscillations are controllable by varying the detuning.

IFCS-EFTF-SPC-9

Short term noise investigation on a compact CPT clock
Danet Jean-Marie, Yun Peter, Guerandel Stephane, de Clercq Emeric
LNE SYRTE, Observatoire de Paris, Paris, France
Email: jean-marie.danet@obspm.fr
Towards the development of on-board atomic clock, alkali vapor cells clocks have shown that besides
their robustness and relative simplicity, cell technology clocks are competitive with the cold atoms
compact setups in term of stability211 212. Among the different vapor cell clock technologies, thecoherent population trapping (CPT) prototype developed at SYRTE offer an alternative where no
microwave cavity is needed. The microwave is optically carried by the frequency difference between
two lasers. Using crossed linear polarized beams and Ramsey temporal interrogation, signals with 15 %contrast and 125 Hz linewidth have been observed. Such a signal, combined with a noise at the shotnoise limit would lead to sub 10-13 τ-1/2 stability clocks. In this paper we report investigations on thenoise processes currently limiting the short term
stability of the clock at the level of 5.5 10-13 at 1s.
Five main noise sources are investigated: magnetic
field, beam polarization, laser frequency, laser
intensity and finally microwave phase. A contribution
to the clock stability below 10-14 at 1s is shown for thetwo first ones. The effect of the optical frequency
detuning has been measured and its conversion on theclock stability is under investigation. The influence ofthe laser intensity noise has been carefully studied, it
is not negligible in the 10-13 range. A stabilization
system has been implemented lowering the RIN of 15
dB down to -137 dB/Hz-1/2 at 160 Hz. Finally the local
oscillator noise contribution to the clock stability has
been studied using the Dick formalism213. This Fig. 69: Sensitivity function of a pulsed CPT clock.
aliasing effect, well understood for a two level system, Pumping 2ms, Free evolution time 4ms, Detection:
had never been investigated for a three level one as 25 µs, 200 µs after switching lasers on.
the CPT. The numerical calculation, in good
agreement with measurements, allowed us to deduce a phenomenological equation for the Dick effect in
CPT, usable for others CPT clocks. The application of those calculations to our prototype pointed out
the local oscillator as main noise source contributor, followed by the intensity noise. Solutions havebeen designed and will be implemented on our set-up. The latest results will be shown at the conference.

211

S. Micalizio et al., Metrologia, vol 49, 425, 2012.

2

F. X. Esnault et al., Phys. Rev. A, 82, 033436, 2010.

3

G. J. Dick et al, in Proc. 19th Annu. Precise Time Time Interval conf., pp. 133–147, 1987.

IFCS-EFTF-SPC-10

MiniAtom: realization of a compact atomic gravimeter
Jean Lautier1, Baptiste Battelier2, Arnaud Landragin1, Philippe Bouyer2
1

LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, 61 boulevard de l’Observatoire, 75014 Paris,
France2
LP2N, CNRS, IOGS, Universite Bordeaux 1, Batiment A30, 351 cours de la Liberation, 33405
Talence CEDEX, France
Email: jean.lautier@obspm.fr

We present here the realization of a highly compact absolute atomic gravimeter. The main purpose is todemonstrate that atomic interferometers can overtake the current limitations of inertial sensors based on“classical” technologies for field and on-board applications. We show that the complexity and thevolume of cold-atom experimental set-ups can be drastically reduced while keeping the performances
close to the state-of-the-art, enabling such atomic sensors to perform precision measurements outside ofthe laboratory.
The measurement of the acceleration of gravity (g) is made with a /2 -  - /2 interferometer using
stimulated Raman transitions to couple |F=1, mf=0> and |F=2, mf=0> hyperfine states of free-falling87
Rb atoms214. The use of an innovative hollow pyramid as the usual retro-reflecting mirror of quantum
inertial sensors enables to perform all the steps of the atomic measurement (trapping and cooling theatoms, performing the interferometer and reading out its outputs) with one single laser beam instead of 6
normally215. The laser system is based on a single telecom laser diode, which is phase modulated andfrequency doubled216. This leads to a drastic reduction of the complexity and the size of the apparatus:
the overall physical package is of a few tens of litters in volume only: the sensor head (that includes thevacuum chamber) fits in a cylinder 40 cm high and 20 cm in diameter; the entire laser bench, theelectronics and the power supplies fit in a cube of 70 cm of side.
We target a relative sensitivity to acceleration of gravity below 10-7 at one shot, which will allow tomonitor time variation of g due to tides and to detect significant mass anomalies and mass
displacements. We have shown promising long-term stability with a flicker floor on the 10 -9 range andup to two day long measurements have been recorded with such architecture2.
Particular efforts have been made to push on the integration of the micro-wave frequency standards used
to drive the clock frequency of 87Rb atoms at 6.835 Ghz and to deliver quantum state selective pulses.
Although an output power of 25 dBm and a 500 MHz agility are required, our chain features a phasenoise that will only limit our relative sensitivity to acceleration at the 10-8 level. We thus show an
attractive trade-off between the integration in a two-litter package and a satisfactory phase noise levelthat other field or on-board quantum sensors could benefit from.
The final assembly of the gravimeter is currently under way and the loading of few 10 8 atoms in a 3D
MOT has already been obtained. The first atomic signals are expected soon.

214

M. Kasevich “Atomic interferometry using stimulated Raman transition”, PRL, vol. 67, p. 181 - 184, 1991.

215

Q. Bodard, “A cold atom pyramidal gravimeter with a single laser beam”, APL, vol. 96, 134101, 2010.

216

G. Stern, “Light-pulse atom interferometry in microgravity”, Eur. Phys. J. D, vol. 53, p. 353 - 357, 2009.

IFCS-EFTF-SPC-11

Spatially Resolved Measurement of Relaxation Times
in a Microfabricated Vapor Cell
Andrew Horsley1, Guan-Xiang Du1, Matthieu Pellaton2, Christoph Affolderbach2,
Gaetano Mileti2, and Philipp Treutlein1
1

2

Departement Physik, Universität Basel, Switzerland
Laboratoire Temps-Fréquence, Institut de Physique, Université de Neuchâtel, Switzerland
Email: andrew.horsley@unibas.ch

Microfabricated vapor cells are an important tool for atomic physics applications, showing particularsuccess in miniaturised atomic clocks217 and DC electromagnetic field sensing218. As a new application,
imaging of microwave magnetic fields using a vapor cell has recently been demonstrated by ourgroup219. A thorough knowledge of the properties of a cell is prerequisite to precision measurements.
For microfabricated cells and imaging applications,
T1 (µs)the spatial dependence of relaxation times andexcitation fields are of particular importance. We
present the spatially resolved characterisation,
performed using time-domain Ramsey and Rabi
measurements, of a 5 mm diameter, 2 mm thickmicrofabricated cell, filled with natRb and 80 mbar of
N2 buffer gas220.
Atomic relaxation is described by the T1 and T2 times,
representing the population and coherence lifetimes,
respectively. The dominant relaxation mechanisms ina vapor cell are Rb-wall, Rb-buffer gas and Rb-Rb
collisions. The coherence lifetime is also limited byinhomogeneities in applied static and microwave
magnetic fields. Both lifetimes can be obtained in asingle time-domain Ramsey measurement.
Fig. 70: T1 times across the cell, obtained using
We characterise T1 and T2 relaxation in the cell as a relaxation in the dark, at a cell temperature of 90°C.
functionofposition,
performing
Ramsey Lifetimes are longer in the centre of the cell, where
the effects of destructive Rb-wall collisions aremeasurements as we scan a narrow laser beam across minimised.
the cell. We also probe the homogeneity of ourapplied static and microwave fields using Rabi sequences. In addition we have implemented an imaging
technique, whereby a CCD chip is used to perform measurements over the entire cell simultaneously. As
an example, figure 1 shows an image of T1 times across our cell.
This work was supported by SNSF and ESA. We thank Y. Pétremand for filling the cell.
217

Svenja Knappe et al “A microfabricated atomic clock” Appl. Phys. Lett. 85, 1460 (2004)

218

D. Budker and M. Romalis, “Optical magnetometry” Nat. Phys. 3, 227 (2007)

219

Pascal Böhi and Philipp Treutlein “Simple microwave field imaging technique using hot atomic vapor cells” Appl. Phys.
Lett. 101, 181107 (2012)
220

M Pellaton, C Affolderbach, Y Pétremand, N de Rooij and G Mileti, “Study of laser-pumped double-resonance clock
signals using a microfabricated cell” Phys. Scr. T149 (2012)

IFCS-EFTF-SPC-12

Towards a Large-Scale, Optical Timing Distribution Systemwith Sub-Femtosecond Residual Timing Jitter
Michael Y. Peng1, Patrick T. Callahan1, Amir H. Nejadmalayeri1, Stefano Valente2,3, Kemal Ahmed2,
Ming Xin2, Eric Monberg4, Man Yan4, Lars Grüner-Nielsen4, John M. Fini4, Tony D. Roberts5,
Philip Battle5 and Franz X. Kärtner1,2
1

Department of EECS and Research Laboratory for Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA
2
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Hamburg, Germany
3
Department of Electrical Engineering and Computer Science, University of L'Aquila, L'Aquila, Italy
4
OFS Laboratories, Somerset, NJ, USA and 5AdvR, Inc., Bozeman, MT, USA
Email: mypeng@mit.edu

Over the past 10 years, we have developed a pulsed optical timing distribution system221 for large-scale,
long-term synchronization of radio-frequency and optical sources in X-ray laser facilities, which may extend
over several kilometers. The system consists of a femtosecond laser tightly locked to a microwave reference
and fiber links stabilized via compact, single-crystal balanced optical cross-correlators (BOCs). Sub-10-fs
performance over days of operation has been achieved222 but is limited mainly by polarization mode
dispersion in standard single-mode fiber. In the near future, it is necessary to improve timing distribution
down to sub-femtosecond precision; current facilities, such as LCLS at Stanford, can already produce X-ray
pulses shorter than 10 fs and concepts for sub-fs X-ray pulse generation are already in place. In the past two
years, we have developed key components and characterized commercial femtosecond lasers suitable forrealizing the next-generation, sub-femtosecond, fiber-based timing distribution system.
As demonstrated by Kim et al.223, BOCs can be used to characterize the timing jitter of mode locked
lasers with attosecond precision. We used this technique to characterize the jitter of two identical,
commercially-available femtosecond lasers (OneFive-ORIGAMI) and confirmed that their high-frequency
jitter for frequencies higher than 1 kHz is less than 70 as (Fig.1a). These lasers therefore have sufficiently
low noise to serve as master oscillators for sub-fs timing distribution. Second, to eliminate slow drifts
induced by polarization mode dispersion, we implemented a 1.2-km polarization-maintaining fiber link using
1 km of standard PM fiber and 0.2 km of novel dispersion-compensating PM fiber from OFS. Link operationfor 16 days showed only 0.9 fs RMS timing drift and during a 3-day interval only 0.2 fs drift (Fig.1b). Lastly,
we present a hybrid integrated BOC fabricated by AdvR using PPKTP waveguides224 (Fig.1c). We seek tosolve long-term drift issues by eliminating alignment drifts in free-space BOCs and to reduce the required
optical power by a factor of 10-100 while achieving similar signal-to-noise levels as those from bulk-crystal
BOCs. With further development, these components can soon be interfaced to realize a completely fibercoupled, sub-femtosecond optical timing distribution system.

Figure 1. (a) Optical-to-optical synchronization of two femtosecond lasers with an integrated timing jitter of 67 as for frequencies above 1 kHz; (b) 1.2-km
timing-stabilized PM fiber link with uninterrupted operation for 16 days with ~0.9 fs RMS timing drift and 3 days with ~0.2 fs drift; (c) Effective timing
sensitivity curve for an integrated PPKTP waveguide operated as a double-pass, balanced optical correlator.

J. Kim et al., “Drift-free femtosecond timing synchronization of remote optical and microwave sources,” Nature Photon., 2: 12, 733–736, 2008.
M. Ferianis et al., "All-optical Femtosecond Timing System for the Fermi@ Elettra FEL," Proc. FEL., Vol 11, 2011.
J. Kim et al., “Attosecond-resolution timing jitter characterization of free-running mode-locked lasers,” Opt. Lett., 32: 24, 3519–3521, 2007.
224
A. Nejadmalayeri et al., “Guided wave optics in periodically poled KTP,” Opt. Lett., 34, 2522-2524, 2009.
221
222
223

IFCS-EFTF-SPC-13

Optical Frequency Transfer over a single-span
1840 km Fiber Link
1

S. Droste, F. Ozimek,2,3 S. M. F. Raupach,2 H. Schnatz,2 G. Grosche,2T. W. Hänsch,1 Th. Udem,1 and R. Holzwarth1
1

Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
3
University of Warsaw, Faculty of Physics, ul. Hoza 69, 00-681 Warszawa, Poland

2

Email: stefan.droste@mpq.mpg.de
The development of optical frequency standards225 raises a demand for transferring highly stable opticalsignals over continental distances. Such transfer would enable new experiments226, and will be mandatory fora future redefinition of the SI-second based on optical frequency standards. We investigate optical frequency
transfer via a 1840 km fiber link connecting Physikalisch-Technische Bundesanstalt (PTB) and Max-PlanckInstitute of Quantum Optics (MPQ). The link consists of a pair of dark fibers227, and is set up in a loop
configuration with sender and receiver located at MPQ. It thus involves a single-span 1840 km stabilization.
We use 20 Erbium-doped fiber amplifiers, and a fiber Brillouin amplifier at each institute, compensating for
420 dB loss.
Fig. 1 shows the instability of the transferredfrequency after 1840 km of fiber for the stabilized
fiber link, expressed as the Allan deviation (ADEV)
and the modified ADEV. The servo bandwidth forthe suppression of fiber-induced noise is limited toabout 27 Hz due to the propagation delay of the lightof around 18 ms. However, the low intrinsic noise of
the fiber link together with active noise cancellation
allow us to reach instabilities (modified ADEV) of
2.7 x 10-15 at 1 s, and about 4 x 10-19 after 100 s ofintegration time. The noise of the link peaks around
15 Hz and is lower at smaller frequencies whichleads to a τ-2 dependency in the modified ADEV as
shown in Fig. 1.

Fig. 71: Fractional frequency instability of the
To assess potential systematic frequency shifts, we 1840 km stabilized link (squares) expressed as
analyzed the mean deviation of the transferred the ADEV. To distinguish between white phase,frequency from the input frequency, and found flicker phase and other noise types the modified
agreement within the statistical uncertainty of 2.6 x ADEV (solid circles) is also shown.
10-19. The results illustrate that for a remotecomparison of state-of-the-art optical clocks, the short-term instability contribution of the stabilized ~2000
km link is negligible within one minute of integration time.
This work was supported by the European Metrological Research Programme EMRP under SIB-02 NEAT-FT. The EMRP is
jointly funded by the EMRP participating countries within EURAMET and the European Union.

225

N. Huntemann, et al., Phys. Rev. Lett. 108, 090801 (2012).

226

C. W. Chou, et al., Science 329, 1630 (2010).

227

K. Predehl, et al., Science 336, 441 (2012).

IFCS-EFTF-SPC-14

A Fiber Optic Gyroscope on multiplexed telecommunication
network with a large enclosed area
C. Clivati1,2, D. Calonico1, G. A. Costanzo1,2, A. Mura1, M. Pizzocaro1,2, F. Levi1
1

Istituto Nazionale di Ricerca Metrologica, Torino, Italy
2
Politecnico di Torino, Torino, Italy
Email: c.clivati@inrim.it

Optical gyroscopes exploiting the Sagnac effect are currently used as optical rotation sensors. Two kindsof devices exist: Fiber Optic Gyroscopes (FOGs) are used in several commercial applications, being
very reliable and robust. They are limited by shot noise and typically achieve resolutions of ~10-6 rad/s1.
On the converse, Ring Laser Gyroscopes achieve higher resolution, being able to detect rotation signals
well below 10-9 (rad/s)/√Hz. They are thus attractive for a detailed study of rotational ground motion
induced by teleseismic waves2,3. However, they are complex experiments using sophisticated optics.
To combine a simple and robust setup with highInternet Data Traffic
Phase modulation
OADM1
resolution, we realized a FOG enclosing a
20
AOM1
CCW
20 km
CW
km2 area4 on a 47 km fiber. The fiber is used for thePS
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CW+CCW
C1
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internet data traffic and has a Dense Wavelength
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CW+CCW
CCW
AOM2
OADM2
Division Multiplexed architecture. The setup is thePD
Frequency
Internet Data TrafficRFsame as for passive FOGs (see Fig. 1). A laser beam
Modulation
990 kHz LO
Feedback Loopis split into two beams that travel over the loop in
opposite directions, acquiring a phase shift that
Fig. 72: Setup of the FOG. PS polarization
depends on the Earth rotation. After a round trip, the scrambler, C couplers, AOM acousto optic
two beams are recombined to detect the Sagnac modulators, OADM Optical Add&Dropphase. A well-known technique of non-reciprocal Multiplexers, CW(CCW) clockwise (counterphase modulation is used to this purpose. We clockwise) propagating beams.
developed a closed loop system in which thenonreciprocal phase is compensated inserting a small frequency offset between the two beams.
Thanks to its large area, this system could be suitable to detect variations in the Earth rotation rate with asensitivity of 10-8 (rad/s)/√Hz, limited by the non-reciprocal mechanical noise of the fiber.
2

At the conference we will present a description of our system, the results we obtained, and an analysis of
the present limitations and of possible perspectives of this technique, also in consideration of the present
widespread of phase-coherent optical links across large geographical areas.
1. A. Velikoseltsev, K. U. Schreiber, A. Yankovsky, J.-P. R. Wells, A. Boronachin, A. Tkachenko, “On the application ofﬁber optic gyroscopes for detection of seismic rotations“ J. Seismol. 16 , 623 (2012).
2. H. Igel, K. U. Schreiber, A. Flaws, B. Schuberth, A. Velikoseltsev, A. Cochard, “Rotational motions induced by the M 8.1
Tokachi-oki earthquake, September 25, 2003”, Geophis. Res. Lett. 32 , L08309 (2005).
3. J. Belﬁ, N. Beverini, G. Carelli, A. Di Virgilio, E. Maccioni, G. Saccorotti, F. Stefani, A. Velikoseltsev, “Horizontal
rotation signals detected by “G-Pisa” ring laser for the M=9.0, March 2011, Japan earthquake”, J. Seismol. 16, 767 (2012).
4 C. Clivati, D. Calonico, G. A. Costanzo, A. Mura, M. Pizzocaro, F. Levi “A Large Area Fiber Optic Gyroscope on
multiplexed fiber network”, accepted for pubblication in Opt. Lett.

IFCS-EFTF-SPC-15

Towards large scale metrological fibre network
Anthony Bercy1, Fabio Stefani1, Olivier Lopez1, Paul-Eric Pottie2, Christian Chardonnet1, Anne AmyKlein1 and Giorgio Santarelli2,31

Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS,
Villetaneuse, France
2
LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France
3
Laboratoire Photonique, Numérique et Nanosciences, Université de Bordeaux 1, Institut d’Optique and
CNRS, Talence, France
Email: paul-eric.pottie@obspm.fr
In the frame of the REFIMEVE+ project, aiming at disseminating an optical frequency standard to morethan 20 laboratories in France, we present the progress made towards a metrological fibre wide-area
network.
As a master piece for building long-haul links in a dark channel approach, we introduced previously
Remote Laser Stations, which act as repeater stations for the metrological signal228. The supervision of
the equipment, and the ability to remotely operate the station, plays a major role for an operational large
scale network. We will first report on the progress for the realization of a remotely operated Remote
Laser Station.
Second we address the question of multiple
users distribution. In that case, a point-to
point network needs a lot of fibers and is not
the optimum solution. In-line extraction, as
first proposed 3 years ago by G. Grosche229,
enables a more flexible distribution : thesignal is extracted from the main link andeither directly distributed to a lab or fed toanother secondary link. Figure 2 displays
the frequency stability at the extraction
together with the end-to-end stability of themain link. The frequency stability at theextraction end is below 5×10-18 at 500 s
integration time thus providing the stability
performance at the same level than with asimple link.

Fig. 73: Frequency Allan deviation for the end-to-end
and extracted-to-end signals, in close and open loop

228

Lopez O., Haboucha A., Chanteau B., Chardonnet C., Amy-Klein A., Santarelli G., “Ultra-stable long distance opticalfrequency distribution using the Internet fiber network,“ Optics Express 20, p 23518-23526, 2012.
2

G. Grosche, “Dissemination of Frequency References to Many Locations Along an Optical Telecommunication Fiber”,
EFTF’2010

IFCS-EFTF-SPC-16

Microwaves generation from mode-locked Er-fiber lasers with
sub-fs-level absolute timing jitter
Kwangyun Jung, Junho Shin, and Jungwon Kim*
Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea*Email: jungwon.kim@kaist.ac.kr
Ultralow phase noise RF/microwave signal sources are important for various science and engineering
applications, ranging from precision time-frequency metrology to future electronic clocks, radar andmeasurement systems. Recently, photonic generation of ultralow phase noise microwave signals using
ultrastable cavity-stabilized CW lasers and optical frequency combs has attracted great interest.230 Also,
we have recently demonstrated that the timing jitter (>1 kHz offset frequency) from free-running modelocked fiber lasers can be engineered well below 1 fs level.231 Therefore, for applications that require
ultralow short-term (<1 ms time scale) timing jitter/phase noise microwave signals, one can directly use
a simple free-running mode-locked fiber laser without state-of-the-art ultrastable cavity references.
In this paper, we show the generation of 10-GHz microwave signals from 78-MHz free-running modelocked Er-fiber lasers with 0.49 fs absolute rms timing jitter integrated from 10 kHz to 10 MHz offset
frequency, with a single-sideband phase noise of -142 dBc/Hz at 10 kHz offset frequency. In order tomitigate the shot-noise-limited high-frequency phase noise in the optical-to-electronic conversion
process (typically limited around -140 dBc/Hz level when standard 100-MHz fiber lasers andphotodetectors are used), we synchronize a low-noise voltage-controlled oscillator (VCO, 10-GHz
dielectric resonator oscillator) to the mode-locked fiber laser using our recently demonstrated Fiber
Loop Optical-Microwave Phase Detector (FLOM-PD)232 with -157 dBc/Hz background noise. Figure 1
shows the experimental setup and the phase noise measurement results. In addition, 600-m remote
generation233 of a microwave signal from a mode-locked Er-fiber laser with 2.7 fs rms relative timing
drift for 7 hours is demonstrated.

230

T. M. Fortier et al. “Sub-femtosecond absolute timing jitter with a 10 GHz hybrid photonic-microwave oscillator,” Appl.
Phys. Lett. 100, 231111 (2012).
231

T. K. Kim et al. “Sub-100-as timing jitter optical pulse trains from mode-locked Er-fiber lasers,” Opt. Lett. 36, 4443
(2011).
3

K. Jung and J. Kim, “Subfemtosecond synchronization of microwave oscillators with mode-locked Er-fiber lasers,” Opt.
Lett. 37, 2958 (2012).
4

J. Kim et al. “Drift-free femtosecond timing synchronization of remote optical and microwave sources,” Nature Photon. 2,733 (2008).

IFCS-EFTF-SPC-17

Optical lattice clocks with 87Sr in a cryogenic environment

Ichiro Ushijima1,2,3, Takuya Ohkubo1,2,3, Manoj Das2,3, Masao Takamoto2,3,and Hidetoshi Katori1,2,3
1
Department of Applied Physics, Graduate School of Engineering, The University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
2
Quantum Metrology Laboratory, Advanced Science Institute, RIKEN, 2-1 Hirosawa,
Wako, Saitama 351-0198, Japan
3
Innovative Space-Time Project, ERATO, JST, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656,
Japan
Email: ushijima@amo.t.u-tokyo.ac.jp
A relative frequency stability of 10-17 has been reached by comparing two Sr optical lattice clocks1. At
this level of stability, the frequency shift due to blackbody radiation (BBR) from the room temperatureenvironment becomes a major limitation for Sr lattice clocks1,2. In order to reduce the uncertainties of
BBR shift, we have developed Sr optical lattice clocks that operate in a cryogenic environment. The
BBR shift for Sr atoms is theoretically calculated to be about 2.4 Hz at 300 K. To reach the uncertainties
of 10-18, the fluctuation and inhomogeneity of the ambient room temperature T has to be controlled towithin ΔT = 0.01 K at 300 K. As the sensitivity of BBR shift varies as T3, the uncertainties can be
decreased by cooling down the environmental temperature. At the temperature of T = 70 K, the BBR
shift reduces to 10 mHz and even with a temperature fluctuation of ΔT = 1 K, clock uncertainties of 10-18
can be reached. We can evaluate the BBR shift directly as a frequency difference of two clocks bycomparing two clocks operating at different environmental temperature.
We realize the cryogenic environment by surrounding the region for clock spectroscopy with acryogenic chamber of few cm3 in volume. In order to introduce atoms and lasers, the chamber has two
apertures with diameters of 0.5 and 1 mm. The uncertainty due to BBR shift caused by the radiation that
irradiates the atoms through these apertures can be reduced to 1×10 -18 by moving the atoms 5 mm inside
the chamber and thereby reducing the solid angle from atoms to the environment to 0.5 msr. The
cryogenic chamber is cooled down to 70 K by a Stirling refrigerator and the temperature fluctuation canbe maintained to within ΔT = 10 mK.
In this poster presentation we will discuss our cryogenic setup for two Sr lattice clocks and the latest
experimental results. By using synchronous interrogation1 and comparing two clocks, one in a cryogenic
and the other in a room temperature environment, the BBR shift can be observed as the frequency
difference of the two clocks with high stability. Comparing two clocks synchronously in a reduced BBR
environment will allow us to evaluate other systematic errors such as atomic interactions and lattice lightshifts with high precision.
＿＿＿＿＿＿＿＿＿＿＿＿
1

M. Takamoto, T. Takano, and H. Katori, “Frequency comparison of optical lattice clocks beyond the Dick limit”, Nat.
Photon. vol. 5, p. 288-292. 2011.
T. Middelmann, Ch. Lisdat, St. Falke, J. S. R. Vellore Winfred, F. Riehle and U. Sterr, “Tackling the blackbody shift in astrontium optical lattice clock”, IEEE Trans. Instrum. Meas.. vol. 60, p. 2550-2557. 2011.
2

IFCS-EFTF-SPC-18

First spectroscopy of the 1S0 – 3P0 transition in Lamb-Dicke
confined magnesium atoms

André Kulosa, Steffen Rühmann, Dominika Fim, Klaus Zipfel, Wolfgang Ertmer, Ernst M. Rasel
Institut für Quantenoptik, Leibniz Universität Hannover, Hannover, Germany
Email: kulosa@iqo.uni-hannover.de
We report on the status of the magnesium optical clock experiment in Hannover. Recently, wedemonstrated the first spectroscopy of the spin-forbidden 1S0 – 3P0 clock transition in µK cold
magnesium atoms that were trapped in an optical lattice at the predicted magic wavelength of 469 nm.
Due to the lack of sub-Doppler cooling techniques, we prepare our atoms using a continuous loading
scheme for an optical dipole trap at 1064 nm234: Atoms with milli-Kelvin temperature are continuouslytransferred to the dipole trap by creating a loss channel for 3P0 atoms. The coldest among them can be
captured by the optical potential for subsequent transfer into the optical lattice.
Applying an external homogeneous magnetic field creates a mixture of the 3P0 and 3P1 states weakly
allowing the 1S0 – 3P0 transition235. Performing such a magnetic field-induced spectroscopy, we havebeen able to de-excite 25% of 3P0 atoms on the 458 nm intercombination transition to the 1S0 groundstate.
The interrogation laser for the ultra-narrow clock transition is a frequency doubled diode laser at 916 nm
stabilized to a vibration insensitive optical cavity. The laser system shows a fractional frequency
instability of y(= 1 s) = 5 x 10-16.
As a next step, we will experimentally investigate the magic wavelength for magnesium.

234
235

M. Riedmann, et al., Phys. Rev. A 86, 043416 (2012)
A. V. Taichenachev, et al., Phys. Rev. Lett. 96, 083001 (2006)

IFCS-EFTF-SPC-19

Optical lattice clocks near the QPN limit: A tenfold improvementin optical clock stability
Travis L Nicholson1, Michael J Martin1, Jason R Williams1, Benjamin J Bloom1, Michael Bishof1,
Matthew D Swallows2, Sara L Campbell1, and Jun Ye1
1

JILA, University of Colorado, Boulder, CO USA
2
AOSense, Sunnyvale, CA USA
Email: nicholtl@jilau1.colorado.edu

-16

10

-17

Exc. Frac.

Up to now lattice clocks with ~1000 atoms have notshown improvement over the stability of single-ion
clocks. Lattice clock stability has been limited bylaser noise (via the optical Dick effect). To address
this problem, we constructed a new clock laser with athermal noise floor of 1×10-16—an order of magnitudeimprovement over our previous clock laser. With thislaser, we compare two lattice clocks, reaching
instability of 1×10-17 in 2000 s for a single clock. Thisinstability is within a factor of 2 of the theoretical
QPN limit for ~1000 atoms, representing the lowest
reported instability for an independent clock238.

Allan Deviation

Two classes of optical atomic clocks have surpassed microwave frequency standards: single-ion clocks
and optical lattice clocks. Single-ion clocks hold the record for the lowest systematic uncertainty236;
however, many-atom lattice clocks237 have the potential to outperform single-ion clocks because thestandard quantum limit to atomic clock instability (known as quantum projection noise or QPN) scalesas (1/Natoms)1/2. For realistic atom numbers andcoherence times, QPN-limited lattice clocks could
Comparison Data
average down to a given stability hundreds of times
Dick Effect + QPN
QPN
10faster than the best ion clocks.
0.8
0.6
0.4
0.2
0

10

0

-10

0

10

Detuning (Hz)

10

1

10

2

10

3

Averaging Time (s)Fig. 74: A comparison between two independent Sr
optical lattice clocks. The stability is 4.4×10-16/τ1/2.
The inset depicts typical scans of the clocktransition (open circles), and the red line is a fit to
the data using the Rabi model.

The high stability of many-particle clocks can come at the price of larger systematic uncertainty due to afrequency shift from atomic interactions. To minimize this shift, we use a cavity-enhanced lattice239 forour second clock. The high circulating power inside the cavity allows for a large trap volume, yielding adensity at 2000 atoms that is 27 times smaller (than in our first clock) and permitting us to trap as manyas 5×104 atoms. For 2000 atoms in our lattice, we measure a value for this shift (which is linear indensity) of -3.11×10-17 with an uncertainty of 8.2×10-19.

236

Chou, et al., PRL 104, 070802 (2010)

237

Ludlow, et al., Science 319 1805 (2008)

238

Nicholson, et al., PRL 109, 230801 (2012)

239

Westergaard, et al., PRL 106, 210801 (2011)

IFCS-EFTF-SPC-20

A 120-µW GSM Phase Noise-Compliant Pierce Oscillator
Referenced to a 61-MHz Wine-Glass Disk Resonator
Thura Lin Naing, Tristan O. Rocheleau, Elad Alon, and Clark T.-C. Nguyen
University of California at Berkeley, Berkeley, California, USA
Email: thura@eecs.berkeley.edu
A 61-MHz Pierce oscillator referenced to a single polysiliconsurface-micromachined wine-glass disk resonator has achieved
phase noise marks of -120dBc/Hz at a 1-kHz offset and 139dBc/Hz at far-from-carrier offsets. When divided down to
GSM’s 13MHz, this corresponds to -133 dBc/Hz at 1-kHz and 152dBc/Hz at far-from-carrier offsets, both of which satisfy
GSM reference oscillator phase noise requirements. This Pierce
oscillator not only provides improvements of 10dB at 1kHz and
7dB at far-from carrier offsets versus a transimpedance amplifier(TIA) topology240 using a similar single disk, it also reduces
power consumption down to only 120µW, which is ~3 times
smaller. Such low phase noise and power achieved by a tiny
MEMS device might soon be key enablers for low power “setand forget” autonomous sensor networks with substantial
communication capability.
Previous TIA-based oscillators1 attained GSM specs by arraying
MEMS devices to boost oscillator loop power to reduce far- Fig. 75: The 61-MHz Pierce oscillator.
from-carrier phase noise. In contrast, the work presented here
achieves the same GSM spec using only a single MEMS
resonator with significant area savings versus the previous large
array. It does this via the remarkably simple Pierce configurationof Fig.1 that yields better performance in two ways: 1) byreducing noise-figure by using only two active transistors; and 2)
by increasing voltage swing, thereby raising oscillator loop
power.
Fig. 2 compares measured phase noise data for a 61-MHz TIAbased oscillator with that of the Pierce oscillator at 61MHz (anddivided down to 13MHz), clearly showing the performancedifference, and from the 13MHz curve, clearly meeting GSM Fig. 76: Measured phase noise of 61-MHz
specs. When power consumption is taken into account using the oscillators and normalized to 13 MHz
popular Figure of Merit (FOM) (given in the plot inset), this (Pierce) for comparison to GSM spec.
performance marks the best FOM at 1 kHz among published on-chip oscillators to date, as illustrated in thetable below.
Device Type
FOM@ 1 kHz (dB)240This work-225

Wine-glass array1-223

FBAR241-220

Quartz242-211

Y.-W. Lin, et al., “Low phase noise array-composite micromechanical ..,” Tech. Dig. IEDM 2005, pp. 287-290.
A. Nelson, et al., “A 22µW, 2.0GHz FBAR oscillator,” RFIC 2011, pp. 1-4.
242
J. T. M. van Beek, et al., “A review of MEMS …,” J. Micromech. Microeng, vol 22, no.1, 2011.
241

IFCS-EFTF-SPC-21

A 2.8 GHz Combined Mode of Vibration Aluminum Nitride MEMS
Resonator with High Figure of Merit Exceeding 45
Yu Hui, Zhenyun Qian and Matteo Rinaldi
Department of Electrical and Computer Engineering, Northeastern University, Boston, MA/USA
Email: hui.y@husky.neu.edu, rinaldi@ece.neu.edu
This paper presents the first demonstration of a high frequency (2.8 GHz), lateral field excited (simple twomasks fabrication process), combined lateral-thickness extensional mode of vibration aluminum nitride(AlN) micro-electro-mechanical (MEMS) resonator with unprecedentedly high figure of merit (kt2Q > 45).
For the first time, a single interdigital electrode was employed to excite a high frequency mode of vibrationin an AlN plate (1.5 µm thick) by making use of both the d33 and d31 AlN piezoelectric coefficients243. The
resulting MEMS resonator showed high quality factor, Q~2000, (thanks to the high quality AlN film directly
deposit on top of the Silicon substrate) and the highest electromechanical coupling coefficient ever reported
for AlN MEMS resonators employing a single electrode, kt2~2.5% (thanks to the coherent combination of d33
and d31 coefficients to transduce one single mechanical mode of vibration).
The use of a single interdigital electrode to excite (lateral field excitation, LFE) a high frequency contourextensional mode of vibration in AlN microstructures has been previously demonstrated244. However, due tothe relatively low d31 coefficient of AlN, the maximum predicted electromechanical coupling coefficient245
for such class of devices is only 1.5%. In this work, by properly optimizing the ratio between the thickness of
the AlN film (t) and the pitch of the interdigital top electrode (Wp) the d33 and d31 coefficients have beencoherently combined and harnessed to transduce one single mechanical vibration mode. The combinedlateral-thickness mode of vibration was simulated using COMSOL showing a maximum value ofelectromechanical coupling coefficient, kt2 = 2.82%, for t/Wp0.94. A device with such optimum t/Wp was
fabricated (Fig. 1), showing high quality factor (Q = 1855) and a value of electromechanical coupling
coefficient (kt2 = 2.48%) ~2 times higher than what is typically achieved with conventional LFE AlN
contour-extensional mode resonators2 (Fig. 2).

Fig. 1: SEM image of the fabricated AlN
combined mode of vibration MEMS resonator.
t/Wp was set to be ~0.94, resulting in aresonance frequency of the 2.8 GHz. It is worth
noting that the fabricated device is fully
anchored to the substrate maximizing power
handling and minimizing electric loss due to243
C. J. Zuo, et al. IEEE IFCS 2012, pp. 1-4.
244 routing.
245

C. J. Zuo, et al. IEEE IFCS 2009, pp. 381-384.
J. H. Kuypers, et al. IEEE IFCS 2008, pp. 240-249.

Fig. 2: Measured admittance curve and BVD model
fitting of the fabricated AlN resonator. High device
figure of merit (FOM = kt2·Q = 46) and low
motional resistance (Rm = 15 Ω) were achieved at
2.8 GHz. The inset shows the 2D FEM simulationof the mode of vibration, indicating a combinedlateral-thickness extensional mode of vibration.

IFCS-EFTF-SPC-22

Close-in Phase Noise Reduction in an Oscillator based on 222
MHz Non-Linear Contour Mode AlN Resonators
J. Segovia-Fernandez, C. Cassella, G. Piazza
Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
Email: jsegovia@andrew.cmu.edu
Phase Noise (PN) reduction in oscillators has been traditionally accomplished by using low noise
amplifiers or high quality factor (Q) resonators, in accordance with Lesson theory246. However, previous
work on nonlinearly driven resonators has suggested that locking the device into a particular nonlinear
state (so-called bifurcation) can help evading the amplifier noise247. AlN Contour Mode Resonators(CMRs) are an emerging class of piezoelectric MEMS devices exhibiting high Q and low motional
resistance at high frequencies (fres). Because of their micron-scale size the AlN CMRs have revealed anonlinear behavior induced by self-heating when driven with relatively high power248. In this work, weshow a substantial improvement of the PN close-in (-20dBc/Hz @ 100Hz) of a 222 MHz oscillator thatincorporates a nonlinearly driven AlN CMR.
The oscillator circuit presented here was built using coaxial electronic components (Fig. 1). The
experiments were carried out by setting the DC bias of the amplifier to 6V, therefore ensuring enoughgain to both sustain oscillations and drive the resonator nonlinearly. The phase shifter was manually
tuned in steps of 5° to increase the circuit delay and, hence, lock the oscillator at different frequencies(fosc) on the non-linear resonance curve of the 222 MHz AlN CMR device. Fig. 2 depicts PN (dBc/Hz)
versus offset frequency (foff) for different phase delays. A dramatic change of slope in the PN close-in(foff<1kHz) is observed when fosc<fres (fres is indicated on the plot). This frequency corresponds to thedevice operating past bifurcation, as we can infer by measuring the resonator admittance in open loop
for the same output power. The data highlight that for particular phase shifts >15°, the PN curve
experiences a significant reduction in slope (from 1/f4 to 1/f2). Furthermore, the experimental results
show that the AlN CMR thermal time constant (τTH)3 limits the maximum foff for which a PN
improvement can be recorded.

246

Fig. 77: SEM of the 222MHz AlN CMR;b) wirebonded AlN CMR on a PCB; andboth c) schematics and d) actual oscillator
setup including (1) AlN CMR, (2) Fig. 78: a) PN vs foff at DC bias=6V and different phase
amplifier, (3) power splitter, and (4) phase shifts (q). b) Open loop amplitude and phase of AlN CMR
admittance for various input powers.
shifter.

D. B. Leeson, “A simple model of feedback oscillator noises spectrum,” Proc. IEEE, vol. 54, pp. 329–330, 1966.
B. Yurke, D.S. Greywall, A.N. Pargellis, and P.A Busch, “Theory of amplifier-noise evasion in an oscillator employing anonlinear resonator,” Phys. Rev. A, vol. 51, pp. 4211-4229, 1995.
248
J. Segovia-Fernandez, A. Tazzoli, M. Rinaldi, G. Piazza, "Nonlinear lumped electrical model for contour mode AlN
resonators," IEEE Int. Ultrasonics Symp., pp.1846-1849, 2011
247

IFCS-EFTF-SPC-23

Lisha Shi1, Gianluca Piazza2
1
Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA, 2Department ofElectrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, USA

Ion-Sliced Lithium Niobate on Silicon Dioxide for Engineering theTemperature Coefficient of Frequency of Laterally Vibrating Resonators
Lisha Shi, Gianluca Piazza
Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
Email: lishashi@andrew.cmu.edu, piazza@ece.cmu.edu
This paper reports, for the first time, on the demonstration of Laterally Vibrating Resonators (LVRs)
based on Y-cut Ion-Sliced Lithium Niobate (LN) thin films on silicon dioxide (SiO 2) (Fig.1a-b). By
adding a thermally grown layer of SiO2 to the resonator stack, it is possible to engineer the temperature
coefficient of the resonator and therefore ensure the use of these devices for applications where tighttemperature specifications are required.
Prior demonstrations of LN LVRs 249, 2
have shown the capability of attaininga high Kt2 (> 20%) and Qs of about
1,000, but exhibited a rather large andnegative temperature coefficient of
frequency (TCF) of about - 80 ppm/°C.
Furthermore, they were built on a LN
substrate with either BCB or SiO2 as
sacrificial layers, which required a wet
etch step for the release of theresonator. In this work, the LN LVR isbuilt on top of a SiO2 layer andreleased from the underlying siliconwafer by dry etching in XeF2. With the Fig.1 (a) Mock-up view of LiNbO3-on SiO2 MEMS microhLN set at 420nm and hSiO2 at 1600nm, resonator (b) Optical image of a 511.8MHz LN LVR. The
this first demonstration (Fig.1b) period of the interdigitated finger was set to be 6 μm withyielded TCF of + 11ppm/°C, + each metal line having a width of 2μm (c) The comparison
18ppm/°C and + 20.4ppm/°C forof the averaged measured and simulated Kt2 for LN on
devices respectively oriented at 80˚, SiO LVRs for various orientations. (d)The measured and250˚, and 20˚ to the x-axis. The positive
fitted admittance response of LN on SiO2 LVRs with Qs in
TCF clearly indicates the effect of theexcess of 1,300 in air
SiO2, matches with FEM simulations, and offers evidence that TCF engineering is possible. Most
importantly, these LN LVRs still exhibited high values of the electromechanical coupling, Kt2, around
6.2% (see Fig.1c) and Qs in excess of 1,300 in air at 419.3 MHz (Fig.1d). By optimizing the relativevalues of hLN and hSiO2 it is ultimately possible to attain devices with zero first order TCF.

1
2

2

R.Wang, S. Bhave, and K. Bhattacharjee “High Kt ×Q, Multi-frequency Lithium Niobate Resonators” MEMS 2013(2013)

S. Gong, L. Shi, G. Piazza, “High electromechanical coupling MEMS resonators at 530 MHz using ion sliced x-cut
LiNbO3 thin film”, International Microwave Symposium (2012).

IFCS-EFTF-SPC-24

Micromechanical Disk Array-Composite for Enhanced
Frequency Stability Against Bias Voltage Fluctuations
Lingqi Wu1, Mehmet Akgul1, Zeying Ren1, Clark T.-C. Nguyen11Dept. of EECS, University of California at Berkeley, Berkeley, CA, USA
Email: wulingqi@berkeley.edu

A 215-MHz polysilicon capacitive-gap transduced micromechanical resonator array employing 50
mechanically coupled contour mode disks (cf. Fig. 1)—the largest such array yet fabricated andmeasured—has achieved 3.5× better frequency stability than single stand-alone disk counterparts against
fluctuations in the dc voltage (VP) normally dropped across the electrode-to-resonator gaps during
device operation. Here, connection of numerous resonators via half-wavelength (λ/2)-dimensioned
coupling beams produces a single array-composite resonator that selectively resonates at a single mode
frequency with all resonators moving in phase. The key to enhanced frequency stability against bias
voltage variation is the electrode-to-resonator
Electrode to
C0
Resonator
Capacitancecapacitance (Co) generated by the parallel combination of
Input
Electrode
input/output electrodes overlapping each resonator in the
d=50nmRP
RP
array. Co dominates among elements loading theBiasresonator and effectively raises its stiffness (beyond theVoltage(V )stiffness increase resulting from mechanical coupling),much like a varactor does in crystal circuits. This in turn
Disk
OutputRP
reduces the efficacy of the bias voltage-controlled Resonatorλ/2 Coupling Electrode250
electrical stiffness . The more resonators in the array,Beamthe smaller the frequency shift imposed by a given bias
Fig. 79: SEM of a 215-MHz 50nm
voltage change. This result suggests that the most stable capacitive-gap transduced contour mode disk
MEMS-based oscillators (e.g., against supply noise and array employing 50 mechanically coupled
acceleration251) are ones that utilize mechanicallyresonators.
coupled arrays of resonators.
Measurement data

Comment [ctn3]: Somewhere in the figure, youneed to show the dc bias.

Frequency Change [ppm]

P

Array

Simulation(N =50)Fig. 2 presents measured curves of frequency versus bias
Arrayvoltage for the array-composite resonator of Fig. 1, all(N = 16)alongside theoretical curves predicted by an equivalentcircuit modeling the above phenomena for arrays with
Singledifferent numbers of resonators. Here, theory andResonator(N = 1)
measurement match quite well. The 50-element 215Array(N = 8)MHz array experiences a 20ppm frequency change when
VP varies by 9V, which represents a 3.5× improvement
DC-bias Voltage VP [V]over the 70ppm of a single resonator and could
potentially improve the acceleration sensitivity of a Fig. 2: Measured curves of resonancefrequency versus dc-bias voltage VP plotted
MEMS based oscillator by 11dB.

against simulation using equivalent circuit
models for resonator arrays with N=1, N=8,
N=16 and N=50.
250Frank D. Bannon III, J. R. Clark, and C. T.-C. Nguyen, “High-Q HF Microelectromechanical Filters”, IEEE J. Solid-State
Circuits, vol. 35, no. 4, pp. 512-526, April 2000.
251

T.L. Naing, T. O. Rocheleau, Z. Ren, E. Alon, and C. T.-C. Nguyen, “Vibration-Insensitive 61-MHz Micromechanical
Disk Reference Oscillator”, IEEE Int. Frequency Control Symposium, Baltimore, Maryland, pp. 276-281, May 2012.

Comment [ctn4]: reference Frank Bannon's JSSC
filter paper.

Compact High-Performance Clocks and Sensors
CLUB H
Tuesday, July 23 2013, 10:30 am - 12:00 pm
Chair:

John Kitching
NISTIFCS-EFTF3-D1-1

Miniature trapped-ion frequency standard with 171Yb+

Peter D. D. Schwindt1, Yuan-Yu Jau1, Heather Partner1, Darwin Serkland1, Adrian Casias1, Ronald
Manginell1, Matthew Moorman1, Robert Boye1, John Prestage2, James Kellogg2, Nan Yu2, Taye
Gebrewold3, Sheng Chang3, Igor Kosvin3, Dan Boschen3
1

Sandia National Laboratories, Albuquerque, NM/USA
2
Jet Propulsion Laboratory, Pasadena, CA/USA
3
Symmetricom, Beverly, MA/USA
Email: pschwin@sandia.gov

We are developing a highly miniaturized trapped ion clock by probing the 12.6 GHz hyperfine transition in
the 171Yb+ ion. The clock development is being funded by the Integrated Micro Primary Atomic Clock
Technology (IMPACT) program from DARPA where the stated goals are to develop a clock that consumes
50 mW of power, has a size of 5 cm3, and has a long-term fractional frequency instability of 10-14 at one
month. Trapped ion systems are an excellent candidate for such extreme miniaturization because ions arewell isolated from the environment independent of the size of the trap. A large degree of miniaturization has
already been demonstrated with the 199Hg+ trapped ion clock developed at the Jet Propulsion Laboratory.252
We will discuss the development of the ion trap physics package and its integration with other key elementsof the frequency standard, including miniaturized laser sources at 369 and 935 nm, a local oscillator, control
electronics, and a microfabricated Yb source for trap loading. We have demonstrated a compact, portableclock system that utilizes a 3 cm3 metal ion trap vacuum package integrated with a magnetic shield, C-fieldcoils, and ion loading and detection systems.253 We have demonstrated continuous operation of the ion clockfor 31 days, and with 49 days of data from several clock runs combined, the long-term fractional frequency
instability of the clock is shown to be in the 10-14 range. Current work is focused on integrating the optics,
laser sources, ion trap drive, and 12.6 GHz microwave synthesizer with the vacuum package.
1E-11

a)

Laser Port

b)
171

Yb
SourceFluorescenceCollection Port

Allan Deviation

Electrical
FeedthroughPhase II Project Goal+
Yb Trapped Ion Clock49 days
49 days, THEO

1E-12

1E-13

US Penny
100

1000

10000

1000001000000

Integration Time, (sec)Fig. 1.(a) Picture of the 3 cm3 vacuum package. (b) Performance of the clock prototype.

252

J.D. Prestage, G L. Weaver, 2007, “Atomic clocks and oscillators for deep-space navigation and radio science,”
Proceedings of the IEEE, Vol. 95 No. 11, pp. 2235-2247.
253

Y.-Y. Jau, H. Partner, P. D. D. Schwindt, J. D. Prestage, J. R. Kellogg, N. Yu, 2012, “Low-power, miniature 171Yb ion
clock using an ultra-small vacuum package,” Appl. Phys. Lett., Vol. 101, pp. 253518.

IFCS-EFTF3-D1-2

Absolute frequency of a trapped atom clock
C. Deutsch+, W. Maineult, V. Dugrain+, R. Szmuk, J. Reichel+, P. Rosenbusch
LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France+
LKB, Ecole Normale Supérieure, CNRS, UPMC, Paris, France

Trapped atoms have become wide-spread for the development of atomic clocks: In optical clocks thetrap absorbs the photon momentum; embarquable clocks benefit from the reduced volume. However,when interrogating an ensemble of many atoms, as wanted for high stability, the confinement enhancesatom-atom interactions and thereby possible frequency shifts.
Operating a microwave clock with 87Rb atoms trapped on a chip [1], we study the effects of interactions.
At ultra-low temperatures, we have observed the opening of an energy gap between the symmetric andanti-symmetric 2-body-wavefunction, which causes spin-locking and gives access to very longcoherence times [2]. Spectroscopy with deliberately inhomogeneous Rabi excitation has provided a
direct measurement of the energy gap [3] and has confirmed the prediction [4], that trapped fermion
clocks, too, may suffer a collisional shift if the excitation is inhomogeneous.
Here we present measurement of the absolute frequency of our trapped atom clock for standard
operation (i.e. homogeneous excitation). We observe an intriguing evolution of the clock frequency with
the Ramsey time. We relate this evolution to the dynamics of spin-locking and develop a model basedon the identical spin rotation effect [5]. We identify a range of parameters presenting particularadvantages to the clock operation. Our findings apply to any trapped boson (fermion) clock, where s(p)wave scattering is dominant.
[1] C. Lacroute et al., IEEE Trans. Ultrason. Ferroelectr. Freq. Control 57, 106 (2010).
[2] C. Deutsch et al., Phys. Rev. Lett, 105, 020401 (2010); G. Kleine Büning et al Phys. Rev. Lett. 106,240801 (2011)[3] W. Maineult et al, Phys. Rev. Lett. 109, 020407 (2012)[4] K. Gibble Phys. Rev. Lett. 103, 113202 (2009)[5] C. Lhuillier and F. Laloë, J. Phys. (Paris) 43, 197 (1982).

IFCS-EFTF3-D1-3

Cancellation of Doppler Shifts in a Cold-Atom CPT Clock
E. A. Donley, F.-X. Esnault, E. Blanshan, and J. Kitching
NIST, Boulder, CO, USA
Email: elizabeth.donley@nist.gov
A compact cold-atom clock based on coherent population trapping (CPT) is being developed that aims
to achieve a timing uncertainty of a few nanoseconds per day. The clock is based on laser-cooled atoms,
which eliminates the buffer-gas shift but in general can introduce a 1st-order Doppler shift since the atom
cloud expands and falls during interrogation. The atoms are interrogated with Ramsey absorption
spectroscopy in the lin || lin CPT254 configuration. This talk will give an overview of the clock design
and function, and will present a systematic evaluation of the 1st-order Doppler shift.

To evaluate the shift, an extra period of free
is inserted before the first Ramsey pulse andatoms are probed from a single direction,
which enlarges the shift so that it can beeasily compared to a basic model.
Measurements of frequency shift versus freeperiod, Ramsey period, and probe direction
very good agreement with a simple
kinematic model for the atoms’ average
position and velocity.
When the atoms are probed symmetricallyalong the direction of gravity, the total shift
the clock’s typical Ramsey period of 6 ms is
consistent with zero and has a current
uncertainty of 1×10-11. The shift magnitude
should be more than an order of magnitude
smaller when the probe direction isperpendicular to gravity.

wave
the
time.
are
CPT

50

TR = 1 ms

45

TR = 2 ms

40

Frequency (Hz)When the atoms are probed with travellingCPT beams along the direction of gravity,
Doppler shift is 3×10-10 for a 10 ms Ramsey
To substantially reduce this shift, the atoms
probed with standing waves by applying
beams symmetrically from above and below.

TR = 6 ms

35

fall
the

30
25
20
15
0

2

4

6

8

10

Free fall time (ms)1214Clock frequency versus extra free-fall time fordifferent Ramsey periods compared to a basic
kinematic model for the Doppler shift. The
offset frequency is the only fit parameter.
Only the signal from the downward beam wasused to calculate the clock frequency, which
maximizes the shift. The full scale (35 Hz)
corresponds to a fractional frequency shift of
5×10-9.

fall
show

for

The clock stability in our unshielded system is presently limited by the Zeeman shift to 2×10 -12 at 1000
seconds of averaging time. A next-generation physics package that includes magnetic shielding is underdevelopment. The new system will be based on an antireflection-coated cell, which should improve thelaser-cooling performance and allow for symmetric standing-wave interrogation with a simple retroreflected CPT beam.

254

A.V. Taichenachev et al., JETP Lett. 82, 398, 2005.

IFCS-EFTF3-D1-4

Rubiclock: towards the first industry-ready cold-atom clock
Luigi De Sarlo1, Baptiste Battelier2, Natascia Castagna1, Michel Lours1, David Holleville1, and NoëlDimarcq1
1

LNE-SYRTE, Observatoire de Paris, CNRS and UPMC, 61 avenue de l’Observatoire, 75014 Paris,
France2
LP2N, Université Bordeaux 1, IOGS and CNRS, 351 cours de la Libération, 33405 Talence, France
Email: luigi.de-sarlo@obspm.fr
We will present the Rubiclock project, an activity started at LNE-SYRTE – Observatoire de Paris two
years ago, funded by ANR and CNES. The project develops a prototype of a vapour-cell clock based oncold atoms which can deliver a short term stability better than that of passive hydrogen maser (relative
instability below 5 x 10-13 at 1s), while at the same time bringing an accuracy specification at the level ofa few 10-15 which is inherently superior to the GPS+H-MASER systems currently in use. We aim at
obtaining these performances while keeping the concept interesting from an industrial perspective.
The operation of the clock is based on the Ramsey interrogation of a sample of ultracold (microkelvintemperature) Rubidium atoms in free fall inside a microwave cavity. Taking advantage of the so-called
isotropic laser cooling255, the atoms are cooled from a vapour directly inside the microwave cavity
thereby eliminating the need of a separate cooling chamber. The use of ultracold atoms allows one tobenefit from interrogation times of several tens of milliseconds at the same time decreasing the effect ofsystematic shifts. Rubiclock represents the evolution of the Cs-based HORACE concept which has
recently demonstrated a short-term stability in the range of 10-13 and long term stability in the range of
10-15 arguably limited by atomic collisions256.
We will present all the subsystems of the clock including a compact laser system at =780 nm based on
frequency doubling of a telecom qualified source257, a new microwave synthesis chain and a newphysical package for optimal thermal management, together with the first scientific results and theperspectives for the industrialisation and an eventual space application of the concept.

255

E. Guillot et al., “Three-dimensional cooling of cesium atoms in a reflecting copper cylinder”, Opt. Lett. 26, p. 1639
(2001)
256

F.-X. Esnault et al., “High-stability compact atomic clock based on isotropic laser cooling”, Phys. Rev. A 82, 033436(2010)
257

F. Lienhart et al., “Compact and robust laser system for rubidium laser cooling based on the frequency doubling of a ﬁberbench at 1560 nm”, Appl. Phys. B 89, p. 177 (2007).

IFCS-EFTF3-D1-5

MiniAtom: realization of a compact atomic gravimeter
Jean Lautier1, Baptiste Battelier2, Arnaud Landragin1, Philippe Bouyer2
1

LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, 61 boulevard de l’Observatoire, 75014 Paris,
France2
LP2N, CNRS, IOGS, Universite Bordeaux 1, Batiment A30, 351 cours de la Liberation, 33405
Talence CEDEX, France
Email: jean.lautier@obspm.fr

We present here the realization of a highly compact absolute atomic gravimeter. The main purpose is todemonstrate that atomic interferometers can overtake the current limitations of inertial sensors based on“classical” technologies for field and on-board applications. We show that the complexity and thevolume of cold-atom experimental set-ups can be drastically reduced while keeping the performances
close to the state-of-the-art, enabling such atomic sensors to perform precision measurements outside ofthe laboratory.
The measurement of the acceleration of gravity (g) is made with a /2 -  - /2 interferometer using
stimulated Raman transitions to couple |F=1, mf=0> and |F=2, mf=0> hyperfine states of free-falling87
Rb atoms258. The use of an innovative hollow pyramid as the usual retro-reflecting mirror of quantum
inertial sensors enables to perform all the steps of the atomic measurement (trapping and cooling theatoms, performing the interferometer and reading out its outputs) with one single laser beam instead of 6
normally259. The laser system is based on a single telecom laser diode, which is phase modulated andfrequency doubled260. This leads to a drastic reduction of the complexity and the size of the apparatus:
the overall physical package is of a few tens of litters in volume only: the sensor head (that includes thevacuum chamber) fits in a cylinder 40 cm high and 20 cm in diameter; the entire laser bench, theelectronics and the power supplies fit in a cube of 70 cm of side.
We target a relative sensitivity to acceleration of gravity below 10-7 at one shot, which will allow tomonitor time variation of g due to tides and to detect significant mass anomalies and mass
displacements. We have shown promising long-term stability with a flicker floor on the 10 -9 range andup to two day long measurements have been recorded with such architecture2.
Particular efforts have been made to push on the integration of the micro-wave frequency standards used
to drive the clock frequency of 87Rb atoms at 6.835 Ghz and to deliver quantum state selective pulses.
Although an output power of 25 dBm and a 500 MHz agility are required, our chain features a phasenoise that will only limit our relative sensitivity to acceleration at the 10-8 level. We thus show an
attractive trade-off between the integration in a two-litter package and a satisfactory phase noise levelthat other field or on-board quantum sensors could benefit from.
The final assembly of the gravimeter is currently under way and the loading of few 10 8 atoms in a 3D
MOT has already been obtained. The first atomic signals are expected soon.

258

M. Kasevich “Atomic interferometry using stimulated Raman transition”, PRL, vol. 67, p. 181 - 184, 1991.

259

Q. Bodard, “A cold atom pyramidal gravimeter with a single laser beam”, APL, vol. 96, 134101, 2010.

260

G. Stern, “Light-pulse atom interferometry in microgravity”, Eur. Phys. J. D, vol. 53, p. 353 - 357, 2009.

Optical Fiber T+F Transfer II
CLUB E
Tuesday, July 23 2013, 10:30 am - 12:00 pm
Chair:

Helen Margolis
National Physical Laboratory

IFCS-EFTF5-D2-1

Controlling distant pulsed laser timing via interferometry
Russell Wilcox1, Ronald Holzwarth2, Giuseppe Rizzelli Martella1, Klaus Hartinger2
1

Lawrence Berkeley National Laboratory, Berkeley, CA/USA
2
Menlo Systems, Martinsried, Germany
Email: rbwilcox@lbl.gov

Ultrafast pump/probe experiments in large laser facilities require femtosecond laser synchronization
over distances of hundreds of meters. Some ways to achieve this use an amplitude modulated carrier or
short optical pulses over fiber. This new scheme1 uses an unmodulated optical wave, synchronizing tothe optical phase. This is an application of frequency metrology techniques in the time domain, utilizing
the full optical bandwidth. Optical nonlinearities (e.g. dispersion and self phase modulation) areavoided. Timing information is carried by optical phase, which provides for sub-femtosecond timing
resolution due to the ~200THz optical frequency.
Our scheme controls envelope timing of CEP (carrier/envelope phase) stabilized comb lasers by locking
the carrier to a transmitted single frequency. Since the CEP stabilization synchronizes the carrier andenvelope, the pulse envelopes are temporally controlled. A clock comb laser provides stable opticalfrequencies, one of which is transmitted via interferometer as a reference.

Fig. 80: Optical timing control scheme. Each subsystem transfers optical phase information to thenext subsystem.

We have recently demonstrated low jitter performance of each subsystem in the timing signal path,
including single frequency selection from the clock (320as), transmission via fiber interferometer(410as), phase locking a fiber modelocked laser to a single frequency (280as), and controlling two comb
lasers via a single frequency (5.6fs). Our current experiment improves the bandwidth of laser control to
1MHz by adding an intracavity EO modulator. Based on optical phase stability results with similar
lasers, we expect sub-femtosecond timing jitter.
1

R. B. Wilcox et al, “Towards attosecond synchronization of remote mode-locked lasers using stabilized transmission of
optical comb frequencies”, J. Mod. Opt., vol. 58, p. 1460-1469, 2011.

IFCS-EFTF5-D2-2

Simultaneous remote transfer of accurate timing and opticalfrequency over a public fiber network
Olivier Lopez1, Amale Kanj2, Paul-Eric Pottie2, Daniele Rovera2, Joseph Achkar2, ChristianChardonnet1, Anne Amy-Klein1 and Giorgio Santarelli2,31

Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS,
Villetaneuse, France
2
LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France
3
Laboratoire Photonique, Numérique et Nanosciences, Université de Bordeaux 1, Institut d’Optique and
CNRS, Talence, France
Email: paul-eric.pottie@obspm.fr
We present a novel method to simultaneously disseminate an ultra-stable optical frequency and accurate
timing over a public telecommunication network on a 540-km optical link simultaneously carrying
Internet data traffic261. An ultra-stable laser is carrying both the frequency and timing signals through thefiber (see Fig. 1). The frequency information is the laser optical carrier frequency. Timestamps signals
are consisting in spread spectrum pseudorandom modulation codes (20 Mchip/s) and are provided by apair of two-way satellite time transfer modems, one for each direction. They are encoded on the opticalcarrier by electro-optic phase modulators. The optical frequency stability results are substantiallyequivalent to the ones reported previously262. The timing stability is below 20 ps for integration time up
to 105 s. The time delay variation remains below 50 ps when the fiber length is scaled from 10 m up to
540 km. This method is very robust, with an overall conservative timing error of about 250 ps
determined by the measured time delay over several weeks of measurement. These results outperformthe satellite techniques. They are easily scalable to a wide area network and open the way to a novel
approach of precise remote synchronization with the potential to realize even better accuracy.

5MHz
&1PPS

Local
Tx

Rx

Optical Phase
Corrector

RF Processing

PD
Ultrastable
Laser L

EOM

AOM
FM

RemoteTx
Rx
RF Processing

540 km
link

PD

PLL

EOM

PC

RIO
Laser 1

FM

Optical frequency stability measurement

Fig. 81: Principle of simultaneous two-way time transfer and frequency transfer
261

Lopez O., Kanj A., Pottie P.E., Rovera D., Achkar J., Chardonnet C., Amy-Klein A., Santarelli G., “Simultaneous remotetransfer of accurate timing and optical frequency over a public fiber network,“ Appl. Phys. B 110, p 3-6, 2013.
262

Lopez O., Haboucha A., Chanteau B., Chardonnet C., Amy-Klein A., Santarelli G., “Ultra-stable long distance opticalfrequency distribution using the Internet fiber network,“ Optics Express 20, p 23518-23526, 2012.

IFCS-EFTF5-D2-3

Remote synchronization via phase-stabilized chirped
continuous-wave frequency transfer
Sebastian M. F. Raupach, Gesine Grosche
Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig,
Germany
Email: sebastian.raupach@ptb.de
Both optical as well as radio or microwave frequency transfer have been demonstrated at relative
instabilities below 10-18 using optical fibres263. For true clock operation and comparison not only acontinuous timescale has to be established, but also means for transferring time information. Local
timescales can then be synchronized to each other (or to TAI). Applications include e.g. very large
baseline interferometry. Recently, several groups1,264,265,4 have demonstrated time transfer, and time andfrequency transfer1,3,4, using glass fibre links. The equipment employed was adopted from satellite twoway time and frequency transfer1,2 or wasdeveloped for achieving a stable delay along afibre link3,266.

263

O. Lopez et al., “Simultaneous remote transfer of accurate timing and optical frequency over a public fiber network“,
Appl. Phys. B, DOI 10.1007/s00340-012-5241-0, 2012, and refs. therein
264

M. Rost et al., “Time transfer through optical fibres over a distance of 73 km with an uncertainty below 100 ps”,
Metrologia, vol. 49, p. 772-778, 2012.
265Ł Śliwczyński, P. Krehlik, A. Czubla, Ł. Buczek and M. Lipiński, “Dissemination of time and RF frequency via astabilized fibre optic link over a distance of 420 km”, Metrologia, vol. 50, doi:10.1088/0026-1394/50/2/133, 2013.
266

B. Wang et al., “Precise and continuous time and frequency synchronization at the 5x10 -19 accuracy level”, Sci. Rep., vol.
2, p. 1-5, 2012.

Here we present results from a proof-of-principle experiment, demonstrating a different technique forremote synchronisation. It is based on the phase-stabilized transfer of a continuous-wave, chirped opticalfrequency, and it is demonstrated via a 150 km underground fibre link in a loop configuration. Using
standard equipment from frequency metrology, it allows for simultaneous optical frequency transfer
with instabilities of the order of 10-19.
Here, we achieve high-fidelity transfer of an optical frequency chirped by more than 100 kHz/s anddemonstrate the suppression of delay related effects. Hence we measure the true offset between twotimescales remotely via the optical link. We find good agreement with results from independent, directside-by-side measurements as shown in fig. 1, which indicates a capability of the technique of around
300 ps. Finally we will discuss how this
82. Accuracy of the timescale offset measurement via
technique can be extended further to yield Figurea phase-stabilized optical link. The error bars indicate thestatistical uncertainties below 1 ps.
combined statistical and systematic uncertainties.
This work was supported by the European Metrology Research
Programme EMRP under SIB-02 NEAT-FT. The
EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union.

IFCS-EFTF5-D2-4

LIFT: The Italian Fiber Network For Frequency and Time
Distribution
R. Ambrosini3, D. Calonico1, C. E.Calosso1, C. Clivati1,2, G.A.Costanzo2, P.Denatale4,G. Galzerano5, F. Levi1, D. Mazzotti4, A. Mura1, N. Poli6, G.M. Tino6, M. Zucco1.
1

INRIM, Istituto Nazionale di Ricerca Metrologica, Torino, Italy
2
Politecnico di Torino, Torino, Italy
3
INAF, Istituto Nazionale di Astrofisica, Bologna, Italy
4
CNR INO, Istituto Nazionale di Ottica, Firenze, Italy
5
CNR IFN, Istituto di Fotonica e Nanotecnologie, Milano, Italy
6
INFN, Istituto Nazionale di Fisica Nucleare, Firenze, Italy
Email: f.levi@inrim.it

LIFT is an Italian national project aimed to realize a backbone structure to distribute along optical fibers,
to a variety of scientific users, high accuracy frequency and time signals, directly derived by INRIM
primary frequency reference.
The project is funded by the Italian Ministry of Research, and allows for a long term rental of thefiber267. In the first stage four cities and five research institutions will be connected together, Torino(National Institute of Metrological Research), Milano (Institute of Photonics and Nanotechnology
belonging to National Research Council, CNR), Bologna (National Astrophysics Institute, VLBIRadiotelescope in Medicina) and Firenze (National
Institute of Nuclear Physics and National Optic Institutebelonging to CNR); we target to connect others scientificand industrial users to the present backbone. The
reference frequency signal will be delivered by INRIM
through a dedicated dark fiber for a total length of 650
km, provided by Italian NREN GARR.
Given the variety of scientific users involved in thisproject and their different needs, both frequency and time(currently under study) dissemination will be
implemented. The four main locations will be equippedwith fiber optic combs to refer all the frequency Path of the LIFT fiber link connecting
measurements to INRIM H-Maser referenced to IT CSF2 Torino, Milano Bologna and Firenze.
and to UTC(IT), or to an Yb lattice clock. LIFT inperspective will link INRIM to other European NMIs and will constitute an important section of a wider
European fiber network connecting NMIs and other scientific and industrial users.
We have already defined a long-standing rental agreement with GARR, to provide us the dark fibers,
and we are now installing our bidirectional amplifiers along the path, expecting to be able to measure theSr clock located in Firenze against INRIM fountain by the end of the year.
267

The connection Torino-Firenze was initially funded by PRIN2009 (2009ZJJBLX ), the realization of a wider network isfunded by “Progetti Premiali 2012”. Both research grants are provided by Italian Research Ministry.

IFCS-EFTF5-D2-5

Time and Frequency Optical Transfer Infrastructure
Vladimir Smotlacha1, Alexander Kuna2, Josef Vojtěch3
1,3

2

CESNET, Prague, Czech Republic
Institute of Photonics and Electronics AS CR, v.v.i.,
Prague, Czech Republic
Email: vs@cesnet.cz

CESNET operates national research network using DWDM (Dense Wavelength Division Multiplexing)
technology. Based on our previous experience with time transfer between Czech and Austrian nationaltime and frequency laboratories, which regular operation started in August 2011, and having access to
own DWDM optical network, we designed and started to build national infrastructure for time andfrequency transfer – TF-infrastructure.
Time and frequency transfer can’t be operated at higher network layers, as they require non-standard,
asynchronous signal modulation with extremely low jitter, and therefore we designed own data coding at
physical layer. We use heterogeneous infrastructure based on both bidirectional and unidirectional
dedicated channels in our productive DWDM network. We proved that there is no interference with any
standard traffic, including data channels 10 and 100 Gbps .
TF-infrastructure goals include:time transfer from existing Cesium primary standards to Laboratory of the National Time andFrequency Standard in UFE – Institute of Photonics and Electronics,comparison of national approximation of UTC with that one in neighboring countries,time and frequency distribution from Cesium clocks and Hydrogen masers.

Links between CESNET and involved organizations utilize available technology, in most cases it is acombination of commercial and open DWDM transmission systems:pair of channels (with the same wavelength in both directions) in a production DWDM optical
network,

pair of DWDM channels with different wavelengths in single fiber bidirectional transmission
system,

pair of DWDM channels (both uni- and bi-directional) in experimental links,

dark fiber – usually last mile in the urban area.

Despite this heterogeneous physical layer, the transport layer provides parameters required for accurate
time (resp. frequency) transfer. Depending on the optical path lengths (20 to 550 km), we reach stability
better than 30 ps in terms of TDEV and 10 -15 in terms of ADEV. Utilized wavelengths are amplified byproductive unidirectional Erbium Doped Fiber Amplifiers (EDFA) or dedicated bidirectional amplifiers
depending on the particular link.
The TF-infrastructure currently connects 6 organizations in the Czech Republic and also Austrian
national T&F laboratory BEV in Vienna. We also operate cross-border link to Polish network Pioneer,
however there are administrative problems to set up time transfer channel to laboratories GUM(Warsaw) or AOS (Borowiec).

Phase Noise & Performances
CLUB D
Tuesday, July 23 2013, 10:30 am - 12:00 pm
Chair:

Jeremy Everard
University of York

IFCS-EFTF2-D3-1

Generalized phase measurement and processing with application in the timefrequency measurement control and link
Wei Zhou, Zhiqi Li, Huimin Song, Qiaoyan Fan
Department of measurement and instrument, Xidian University, Xi’an, China
Abstract
Traditional phase measurement is limited by identical frequency nominal values of two comparing
signals. In a lot of applications, there are higher requirements on not only measurement accuracy, butalso the frequency range of comparing signals. In the area of precise frequency source synchronizationand link, phase processing, measurement between completely different frequency signals are required in
the accuracy and stability transmission of frequency signals with complex relationship. Through the past
20 years’ study that we found some concepts and features which can reflect the phase relationshipbetween the different frequency signals, such as the Least Common Multiple Period, Quantitative Phase
Difference Step, Equivalent Phase Comparison Frequency, and the continuous phase difference groupcharacteristics with an interval of the least common multiple period and quantized phase step according
to specific frequencies between the two different nominal frequency signals. Phase processing can beused between not only the same nominal frequencies but also the different nominal frequencies. The
breakthrough in the phase comparison can lead to realize the frequency &phase measurement
instruments with higher resolution and the new high performance Phase-locked loop device. At the sametime the complex frequency link with high precision and the reform of different quantum frequency
standard can be realize. it also improve the performance. As phase processing generalized in concepts
and technical realization, it will not only advance the time &frequency measurement, control andfrequency source technology, but also can take advantage in wider application fields.

IFCS-EFTF2-D3-2

Source Impedance Influence on Cross-Correlation Phase Noise
Measurements
Jason Breitbarth
Holzworth Instrumentation, Boulder, CO USA
Email: jason@holzworth.com
The phase noise floor of a source has been shown both theoretically and experimentally to be the ratio ofsource power divided by the phase component of the noise power. In a 50Ω system this is determined
by POUT – 177dBm in dBc/Hz. Recent measurements have shown what appears to be better thantheoretical noise floors in some oscillators, assuming a 50Ω environment. However, oscillators rarely
exhibit an output impedance of exactly 50Ω and vary significantly farther from the carrier. While theinput impedance of a modern cross correlation analyzer may be 50Ω, the assumption this load noise iscommon between both channels is incomplete. This leads to the possibility that the extremely low phasenoise measured is real and not in violation of theoretical limits. This paper presents theoreticalarguments and measurements demonstrating the assumptions for these limits are merely incomplete.
The impedance outside the 3dB point of the resonator within an oscillator becomes relevant in low noise
systems. Depending on the architecture of the resonator and how the power is delivered out ofoscillator, the output impedance far from the carrier may be either a good match or nearing an open or
short circuit. This paper deals with the latter. In the short circuit scenario, the output impedance will bevery low far from the carrier and the equivalent noise impedance is also reduced proportionally. Far
from the carrier source impedance therefore may not be considered to be the same as the center
frequency of the source power and the signal to noise ratio of the oscillator may have a different
theoretical limits based on offset frequency relative to the carrier power.
The cross correlation phase noise engine, if designed appropriately, can be viewed as two independent
loads in terms of noise. With noise incoherent loads for each channel, the cross correlation phase noiseengine has the ability to analyze source impedance other with other than 50Ω. The received source
power is still measured as a voltage in a 50Ω environment and is consistent to a power meter.
In consideration of the cross correlation phase noise engine with a frequency dependent source
impedance, measurements exceeding the theoretical limit of a 50Ω system is both theoretically andpractically possible. The abnormally low measurements do not violate theoretical limits once both theproper source impedance and measurement methods are taken into account.
This paper presents the signal to noise analysis both theoretically and experimentally in terms of source
impedance utilizing cross correlation analysis. The experimental data is shown both at base band and at
microwave frequencies. The experimental setup uses an additive phase noise measurement with theintroduction of variable source impedance to demonstrate the theoretical limits.

IFCS-EFTF2-D3-3

Phase Noise Measurement Techniques, Associated Uncertainty and Limitations
Ulrich L. Rohde, Ajay K. Poddar
Synergy Microwave Corp., Paterson, NJ 07504, USA (Email: akpoddar@synergymwave.com)
One of the important parameters of oscillators is phase noise andthere are several methods explaining how to do this and the right one
must be chosen when performing measurements. It is necessary to know
the weakness and strength of different measurement systems, because
none of these methods is perfect for every situation. In general,measuring phase noise is more difficult than measuring amplitude or
frequency and phase related properties. The major challenge is therequirement of huge dynamic range in the phase noise measurement
process [1]-[2].
The new generation of Crystal Oscillators and SAW oscillator exhibits
superior phase noise performance: Close-in phase noise: -149dBc/Hz @100 Hz offset and noise floor ~ -195dBc @ 100 kHz offset from thecarrier of 100 MHz OCXO. SAW resonator based oscillator exhibits 165dBc/Hz @ 10 kHz offset from the carrier frequency of 1GHz andnoise floor is better than 180dBc. The phase noise performance of ultra
low noise Crystal oscillator has been driving the specifications of phasenoise analyzers and it is time consuming exercise to measure the noise
floor below the KT of -177dBm for SSB and 0 dBm output powers.
Once adequate for advanced designs, a noise floor dictated by SSB
thermal noise (Johnson Noise) KT of -177dBm for zero dBm output
power is not enough anymore for some special requirement and also
marketing of these reference frequency sources. The noise correlation
technique allows us to look below KT level (< -177dBm). But theusefulness of the noise contribution below KT is debatable in theperspective of following: reliability, accuracy, speed of test, range,
repeatability, data retrieval, and cost. Despite all these hazards, automatic
phase noise measurement systems have been developed successfully [2][3].
For validation, we build the ultra low noise 100 MHz Crystal
oscillator and noise measurement is conducted using different
equipments (Agilent E5052B, R&S FSUP, Holzworth, Noise XT, andAnapico APPH6000-IS) available on the market. Figures (1), (2), and(3) show the block diagram of ultra low noise 100 MHz crystal oscillator,
theoretical phase noise plot and noise floor of PN equipment using delayline, PLL and cross-correlation techniques. Table 1 describes thetheoretical calculated and measured phase noise on different test
equipment for comparative analysis of phase noise data under similar test
condition.

Noise Feedback
DC-Bias10 V, 80mA

RFout= 14dBm
Buffer
AmplifierBase

3-Terminal BJT/FET(Active-devices)

Collector

Mode-Coupled
Delay Feedback

Noise-Filtering
N/W

Adaptive-Tuned
Filter Network

Improves far offset
noise performance

100 MHz
Crystal Resonator

Injection-Locking
N/W

Injection Locking
Improves close-in
noise performance

Phase Shifter # 1
Phase Shifter # 2

Phase-shifted differential signal fed to resonatorand active device for improved jitter performanceFig 1: Block diagram and prototype of low phase noise 100 MHz
Crystal oscillator for evaluation on different PN Equipments

Fig 2: Theoretically calculated Phase Noise Plot for 100MHz
Crystal Oscillator circuit (LNXO 100) as shown in Figure (1)The theoretical analysis, experimental outcome and observation Fig.3 Typical predicted phase noise plots for 100MHz OCXO andconclude that there is uncertainty and limitation of phase noise noise floor for 3-techniques (PLL, Delay-line, and cross-correlation)measurement equipments. For example, if the equipment in use, after
many correlations gives out a better number, it violates the laws of physics and if it gives a worse number, then either the correlations
settings needs to corrected or the dynamic range of the equipment is insufficient. This measurement is exhaustive, but it was necessary to
explain how things fall in place. At 20dBm output, the output amplifier certainly has a higher noise figure, as it is driven with more power
and there is no improvement possible. There is an optimum condition and some of the measurements showing -200dBc/Hz @ 100 kHz
offset for 100 MHz OCXO advertized are dubious for exactly these reasons. In addition to this uncertainty in phase noise measurement due
to: harmonics, output load mismatch, output phase match, cable length, sweet-spot, dynamic range can lead to error of 10-20dB, which isscary. The theoretical treatment and PN measurement related problems with possible cure will be discussed in full length paper.
[1]
[2]
[3]

D. Calbaza, C. Gupta, U. L. Rohde, A. K. Poddar, “Harmonics Induced Uncertainty in Phase Noise Measurements”, MTT-S Digest, pp. 1-3, June 2012
Rubiola and F. Vernotte. (2010, Feb 27). The cross-spectrum experimental method [http://arxiv.org/, document arXiv:1003.0113v1]
W. F. Walls, “Cross-Correlation Phase Noise Measurements”, 1992 IEEE FCS, pp. 257-261

IFCS-EFTF2-D3-4

Phase noise of optomechanical oscillators
King Yan Fong, Menno Poot, Xu Han, and Hong X. Tang
Department of Electrical Engineering, Yale University, New Haven, CT 06520, USA
Email: kingyan.fong@yale.edu
Cavity optomechanics describes a system consists of an optical cavity coupled to a mechanical resonatorthrough the optical force. When the optical cavity is blue-detuned, the optical force provides a positive
feedback that can drive the mechanical resonator into self-sustained oscillation. Such oscillations havebeen demonstrated in various structures such as micro-toroids268, flexural beams269, photonic crystals270,
micro-rings271, and micro-disks272 resonators, with an oscillating frequency ranging from MHz to GHz,an oscillating mass from ng down to tens of fg, and threshold powers as low as a few μW. This
technology promises to build oscillators that are on-chip integrated, scalable, CMOS-compatible, withlow phase noise and low operating power. However, so far there is still lack of theoretical understandingthat can deterministically predict the oscillator phase noise spectrum. In this talk, we will present ourwork in this aspect.
Fig. (a) shows an example of an optomechanical oscillator made in our lab, which has an opticalwhispering-gallery mode coupled to a mechanical radial breathing mode. We analyze the system bytreating it as a feedback loop, as illustrated in Fig. (b), with the thermomechanical force noise and thelaser light as the inputs. We linearize the equations of motion at a limit-cycle solution273 and derive thenoise transfer functions for each of the loop components. The amplitude noise and the phase noise canbe treated in a unified approach by using the complex number notation and the noise transfers between
phase-phase, amplitude-amplitude, and phase-amplitude are fully quantified. As a result, the phase noise
spectral density of the closed-loop system can be computed once the input noises are known. We
consider the oscillator phase noise contributions for three kinds of noise sources: thermomechanicalforce noise, laser shot noise, and a 1/f technical laser phase noise. As an example we calculated theindividual and combined phase noise spectra for the systems demonstrated in Ref. 2 and 5 shown in Fig.
(c).

268

H. Rokhsari, T. J. Kippenberg, T. Carmon, and K. J. Vahala, Opt. Express, vol. 13, p. 5293, 2005.

269

G. Anetsberger, et al., Nature Physics, vol. 5, p. 909, 2009.

270

M. Eichenfield, J. Chan, R. M. Camacho, K. J. Vahala, and O. Painter, Nature, vol. 462, p. 78, 2009.

271

S. Tallur, S. Sridaran, and S. A. Bhave, Opt. Express, vol. 19, p. 24522, 2011.

272

W. C. Jiang, X. Lu, J. Zhang, and Q. Lin, Opt. Express, vol. 20, p. 15991, 2012.

273

M. Poot, K. Y. Fong, M. Bagheri, W. H. P. Pernice, H. X. Tang, Phys. Rev. A, vol. 86, p. 053826, 2012.

IFCS-EFTF2-D3-5

ULISS project : 2013 progress report
Vincent Giordano1, Serge Grop2, Benoît Dubois2,, Jean-Louis Masson1,
Gregory Haye1, Enrico Rubiola1
1Time and Frequency Dpt., FEMTO-ST Institute, Besançon, France
2
ULISS-ST, SAIC UNiv. Franche-Comté, Besançon, France
Email: giordano@femto-st.fr

The ULISS Cryogenic Sapphire Oscillator (CSO) offers unprecedented short-term frequency
performances. It was specially designed to be transportable by car in order to test this newtechnology in different European sites. During the last 18 months, it was used to qualify withsuccess few high stability frequency sources [1,2,3]. In February 2013, a new measurement
campaign was lead at CNES, Toulouse (France) to qualify the flight model of the frequency
synthesis of the PHARAO clock.
During the same period we built a second CSO unit basedon the same design and conducted new characterisations offrequency stability and environmental sensitivity.
Optimisation of the system has led to an improved
frequency stability reaching currently 1x10 -15 at 10,000 s
integration times. Newly developed digital electronic
controls were also implemented that makes the system
more reliable and versatile/upgradable. Eventually wedeveloped a new low phase noise and high-resolution
frequency synthesis delivering 10 GHz, 100 MHz and9.192 GHz ultra stable signals.
In this paper we draw a progress report on the ULISS
project, updating performances and describing the latest
experiments conducted with our CSO in different sites in
Europe.

Fig. 83: The CSO ULISS[1] ULISS: A Mobile Cryogenic Ultra-Stable Oscillator. S. Grop et al. Proc. of the 2011
EFTF/IFCS Joint Meeting, San Francisco (CA), US, May 2-5, 2011.
[2] Direct comparison of two Cryocooled Sapphire Oscillators presenting relative frequency
instability at the 10−15 level . S. Grop et al. Proc. of the 2012 EFTF, Gothenburg, Sweden, 2426 April 2012.
[3] New Generation of Cryogenic Sapphire Microwave Oscillator for Space, Metrology and
Scientific Applications. V. Giordano et al. Rev. of Scientific Instruments, 83, (2012)

Ultra-stable lasers and resonators
CLUB H
Tuesday, July 23 2013, 02:00 pm - 03:30 pm
Chair:

Longsheng Ma
East China Normal University

IFCS-EFTF6-E1-1

Tenfold reduction in Brownian noise with crystalline coatings
Garrett D. Cole1,2, Wei Zhang3, Michael J. Martin3, Jun Ye3, and Markus Aspelmeyer11

Vienna Center for Quantum Science and Technology (VCQ),
Faculty of Physics, University of Vienna, A-1090 Vienna, Austria
2
Crystalline Mirror Solutions GmbH, A-1090 Vienna, Austria
3
JILA, National Institute of Standards and Technology, and University of Colorado,
Boulder, Colorado 80309-0440, USA
Email: garrett.cole@univie.ac.at

Coating Brownian noise,274 driven by excess mechanical dissipation in high reflectivity ion-beam
sputtered (IBS) films imposes a severe limit on the performance of state-of-the-art precision
measurement systems, such as stabilized lasers for optical atomic clocks and interferometricgravitational wave detectors. As a consequence, a concerted effort has been focused on the identificationof multilayer materials capable of simultaneously achieving high reflectivity and minimal mechanicaldissipation. Recently, AlGaAs resonators have displayed an exceptional mechanical quality factor, Q, up
to 4×104 at room temperature.275 This stands in stark contrast with the Q of SiO2/Ta2O5, which istypically a few thousand.
Building upon advances in semiconductor microfabrication,
we have successfully implemented low-loss epitaxial
multilayers in a standard optical reference cavity design. Our
novel coating technology entails the selective removal of
crystalline films from the original growth wafer, followed bydirect bonding to an arbitrary (curved or planar) opticalcomponent. Here, we present the optomechanicalperformance of cavity end mirrors based on a 40.5-period(6.83 µm thick) GaAs/AlGaAs Bragg reflector directlybonded to fused silica.
Using a pair of bonded mirrors contacted to a 35-mm
zerodur spacer, we confirm that our “crystalline coatings”
Fig. 84: Thermal-noise-limited NPSD of theexhibit both high reflectivity and an intrinsically low
cavity-stabilized 1064-nm laser, with a 0.7 Hz
mechanical loss. Optical ringdown at 1064 nm yields alinewidth (0.5 Hz resolution bandwidth) shown infinesse of 1.5(1)×105, in excellent agreement with thethe inset.
theoretical estimate of 1.53×105. We next probe the coating
loss angle through a direct measurement of the cavity thermal noise (Fig. 1). This is realized by locking
a solid-state 1064 nm Nd:YAG laser to the crystalline coating cavity. A 698 nm Sr lattice clock laser276
acts as a reference, while an Yb fiber comb277 is used to transfer the frequency stability between thesources. We extract a loss angle (1/Q) of 0(4)×10-5 for the bonded AlGaAs mirrors, a tenfold reduction
when compared with the best dielectric multilayers. These results pave the way for a significant
advancement in the sensitivity of optical interferometers, as well as a new level of performance forcavity-stabilized laser systems.
274

G. Harry et al., Optical Coatings and Thermal Noise in Precision Measurement. Cambridge University Press, 2012.
G. D. Cole, Proc. SPIE Optical Trapping and Optical Micromanipulation IX, vol. 8458, 8458-07, 2012.
276
T. L. Nicholson et al., Phys. Rev. Lett. vol. 109, 230801, 2012.
277
C. Benko et al., Opt. Lett. vol. 37, pp. 2196-2198, 2012.
275

IFCS-EFTF6-E1-2

Ultra-stable laser with fractional long-term drift below 10-20/s
C. Hagemann1, T. Legero1, T. Kessler1, C. Grebing1, U. Sterr1, F. Riehle1,
M. J. Martin2, L. Chen2, and J. Ye2
1

Physikalisch-Technische Bundesanstalt (PTB), 38116 Braunschweig, Germany
2
JILA/NIST, University of Colorado, 440 UCB, Boulder, CO 80309-0440
Email: christian.hagemann@ptb.de

Recently, we have set up a cavity-stabilized laser system that has demonstrated so far unreached short-term
1( )stabilities offor averaging times of. This performance below the2
thermal noise limit of state-of-the-art glass resonators has been enabled by the use of a cryogenic singlecrystal silicon cavity.
Material creep is absent in single-crystal
cavities3 and thermal expansion is suppressedby operating the cavity close to a temperatureof 124.2 K, where its coefficient of thermal
expansion is zero. Thus, the silicon cavity
can in principle provide an excellent longterm length-stability.
Utilizing a frequency comb, the frequency
instability of the laser operating atand locked to the silicon cavity has been
evaluated in comparison to a hydrogen maser Fig.85: Frequency record of the laser stabilized to thereferenced to a primary caesium fountain silicon cavity relative to a hydrogen maser and a 87Sr
standard and to a 87Sr optical lattice clock4,5 optical lattice clock at PTB (moving average, window:⁄ of the maser). An average drift of
at PTB. The observed average drift againstwith respect to the Cs fountain clock has been
⁄ in a time removed.
the Cs fountain wasinterval of about one week, which is in good
agreement with the average frequency drift of the laser to the strontium clock ofThese values⁄ . The fractional frequency instability of thecorrespond to a fractional frequency drift of less thanlaser was below ( )for averaging times ofand reached a minimum of(). For longer averaging times up to, the frequency instability increases, but
remains below the frequency instability of the hydrogen maser of. Only at much longer
time-scales the instability of the laser is visible with respect to the hydrogen maser.
____________________________
1

T. Kessler et al., Nature Photonics, 6, 687-692 (2012).

2

T. L. Nicholson et al., Phys. Rev. Lett., 109, 230801 (2012).

3

R. Storz et al., Opt. Lett., 23, 1031-1033 (1998); J. G. Hartnett et al., Appl. Phys. Lett., 100, 183501 (2012).

4

St. Falke et al., Metrologia, 48, 399 (2011).

5

C. Hagemann et al., IEEE Trans. Instrum. Meas, DOI: 10.1109/TIM.2013.2242597 (2013).

IFCS-EFTF6-E1-3

Ultra-Stable Cryogenic Optical Resonators – Towards a Thermal
Noise Limited Frequency Stability < 3·10-17
Moritz Nagel, Katharina Möhle, Klaus Döringshoff, Sylvia Schikora,
Evgeny V. Kovalchuk, and Achim Peters
Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
Email: moritz.nagel@physik.hu-berlin.de
Many experimental and technical applications, e.g. optical atomic clocks, demand ultra-stable opticalresonators for laser frequency stabilization. Nowadays, the frequency stability of all optimized roomtemperature optical reference cavities is limited by the displacement noise within the resonator
substrates and mirror coatings due to thermal noise. The rather straightforward method to simply reducethe influence of thermal noise by cooling down the resonators to cryogenic temperatures is not wellapplicable for most room-temperature cavities.
Therefore, we worked out a special design for an ultra-stable sapphire optical cavity system operating at
4 Kelvin, with a prospective thermal noise limited frequency stability better than 3•10-17 (see Fig. 1). We
will present details on the design of this ultra-stable system as well as first frequency stability
measurements conducted by direct comparison of two such new sapphire optical cavities.

Fig. 1: Left Comparison of the predicted rel. freq. stability of our newly designed cryogenic optical resonators(newCORE operated at 4K, black line) with the measured stabilities of the best room temperature cavities (ultralow-expansion glass, Young et. al [NIST 1999] green line and Jiang et. al [NIST 2010] orange line) as well as
measured stability of the best optical reference cavity (silicon cavity operated at 124K, Kessler et. al [PTB 2012]
purple line). The dashed lines indicate the theoretical thermal noise limits at the operating temperatures. Upper
Right Illustration of the optimized design of our new COREs superimposed with a FEM simulation of verticalvibration (gravitational) induced bending (deformation scaled up by a factor of 1010). Lower Right Picture of oneof the new sapphire cavities mounted on a copper support.

IFCS-EFTF6-E1-4

Laser Frequency Stabilization Using Micro Resonators
Lukas Baumgartel1,2 and Nan Yu1
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
2
Department of Physics, University of Southern California, Los Angeles, CA, USA

1

Email: nan.yu@jpl.nasa.gov
Optical frequency standards and clocks with impressive precision have been demonstrated. Efforts arebeing made for more portability and compactness of these high performance devices. To that end, we
have been investigating the possibility of using optical micro resonators as frequency reference cavities
in place of conventional Fabry-Perot cavities. The micro resonators used are high-Q crystalline
whispering gallery mode (WGM) resonators with linewidths on the order of kilohertz -- comparable tohigh-finesse Fabry Perot cavities -- yet of just millimeters in diameter and inherently robust toacceleration.
A primary challenge of using WGM resonators as reference cavities is stabilizing the eigenmode
frequency itself due to thermal effects. The common thermally stable materials such as ULE are notsuitable for WGM resonators due to poor optical transparency. Small WGM mode volumes inside
dielectric bulk also increase fundamental noise level. Nevertheless, when properly implemented, micro
resonators can potentially provide high frequency stability suitable for optical frequency standards1.
We are investigating the feasibility of the micro resonator reference through both passive and active
stabilization approaches. In the active approach, a dual-mode temperature stabilization method has been
demonstrated2, which suppresses the overall temperature coefficient of the cavity to 1.7×10-7 K-1 – just 6
times higher than that of commercial ultra-low expansion glasses. This actively temperature-stabilized
resonator has already reached a fractional frequency stability of 1x10-12 at one second.
In the passive stabilization scheme, we investigate a number of thermal compensation schemes
employing a hetero-structure to reduce the WGM resonator’s temperature sensitivity. In one approach,
we showed through modeling that a surface coating of compensating material can create a resonatorwith a temperature-coefficient turning point near room temperature3. However, the technique is limited
by material choices and fabrication precision. Currently, we are investigating a compound structure
where the resonator is made of two or more materials of different thermal and mechanical properties.
Significantly, our simulations show that existing low thermal expansion materials can be utilized tosuppress the temperature coefficient of the resonator. Experimental efforts are under way, and we will
present our latest results.
1“Whispering-gallery-mode resonators as frequency references. II. Stabilization,” A. A. Savchenkov, A.
B. Matsko, V. S. Ilchenko, N. Yu, and L. Maleki, Journal of The Optical Society Of America B-Optical
Physics, Vol.24, pp2988-2997 (2007).
2“Frequency stability of a dual-mode whispering gallery mode optical reference cavity,” L. M.
Baumgartel, R. J. Thompson, and N. Yu, OPTICS EXPRESS Vol. 20, p29798 (2012).
3
L. Baumgartel, R. Thompson, D. Strekalov, I. Grudinin, and N. Yu “Whispering Gallery Mode
Resonators as Optical Reference Cavities,” Proceeding of FCS-EFTF, 2011.

IFCS-EFTF6-E1-5

Laser local oscillators for optical atomic clocks
David R. Leibrandt, Shon M. Cook, Michael J. Thorpe*, Chin-Wen Chou**, Tara M. Fortier, Scott A.
Diddams, James C. Bergquist, and Till Rosenband
National Institute of Standards and Technology, Boulder, CO, USA*
Present address: Bridger Photonics, Bozeman, MT, USA**
Present address: Sandia National Laboratories, Albuquerque, NM, USA
Email: david.leibrandt@nist.gov
We stabilize the frequency of lasers by use of spectral holes in cryogenically cooled Eu3+:Y2SiO5, oralternatively by use of acceleration insensitive Fabry-Pérot cavities.
Laser frequency stabilization via spectral-hole burning has the potential to extend laser coherence
beyond what is possible with Fabry-Pérot cavities278. Several properties of Eu3+:Y2SiO5 spectral holes
are measured279, including an upper bound of the thermomechanical noise floor at 3.410-17 (50 %confidence). The absolute frequency has an Allan
deviation of 0.8+1.1-0.210-16 (1000 s averagingtime) and a typical drift rate of 310-17/s (seeFig. 1). This instability is attributed to technicalnoise sources.
For field applications, robust and compact
spherical Fabry-Pérot cavities exhibit an Allan
deviation of 210-15 and a passive acceleration
sensitivity of 2(1)10-11/g that is reduced to below
10-12/g by use of feed-forward techniques280. The
entire laser system fits inside a 464629 cm3
enclosure and its mass is 29 kg, a form-factor thatis suitable for applications281 like geodesy and Fig. 86: Optical frequency comparisons of a laser
locked to 1.0 at. % Eu3+:Y2SiO5 site 1 spectral hole
low-phase-noise microwave synthesis.
patterns at 3.65 K with a Fabry-Pérot cavity, an Al+

The latest results from both experiments will be optical atomic clock, and a second spectral holepresented. This work is supported by ONR, burning optical frequency reference. Linear
AFOSR, and DARPA.
frequency drift is removed.
The predictedfrequency noise due to laser path length fluctuations
and cryostat temperature fluctuations are shown inblack.
278

M. J. Thorpe, L. Rippe, T. M. Fortier, M. S. Kirchner, and T. Rosenband, “Frequency stabilization to 610hole burning,” Nature Photonics 5, 688–693 (2011).

-16

via spectral-

279

M. J. Thorpe, D. R. Leibrandt, T. Rosenband, “Shifts of optical frequency references based on spectral-hole burning in
Eu3+:Y2SiO5,” arXiv:1210.4458 (2013).
280

D. R. Leibrandt, J. C. Bergquist, and T. Rosenband, “Cavity-stabilized laser with acceleration sensitivity below 10 -12 g-1,”
Phys. Rev. A 87, 023829 (2013).
281

D. R. Leibrandt, M. J. Thorpe, J. C. Bergquist, and T. Rosenband, “Field-test of a robust, portable, frequency-stable laser,”
Opt. Express 19, 10278 (2011).

Two-Way Satellite Time and Frequency Transfer
CLUB E
Tuesday, July 23 2013, 02:00 pm - 03:30 pm
Chair:

Victor Zhang
NISTIFCS-EFTF5-E2-1

Development of Carrier Phase Two-Way Satellite
Frequency Transfer at NICT
Miho Fujieda1, Tadahiro Gotoh1, Masanori Aida1, Jun Amagai1, Fumimaru Nakagawa1,
Hideo Maeno1, Ryo Tabuchi1, Yuko Hanado1
1

Space-Time Standards Laboratory, National Institute of Information and Communications
Technology, Koganei, Tokyo, 184-8795, Japan
Email: miho@nict.go.jp

Optical frequency standards require precise frequency transfer techniques to confirm the reproducibility.
Optical fiber transfers already demonstrated the high performance. However, the establishment of anintercontinental link remains an issue. The National Institute of Information and Communications
Technology has contributed to the development of advanced two-way satellite time and frequency(TWSTFT) techniques. In general, the measurement precision of TWSTFT is determined by the groupdelay precision of the pseudorandom noise signal. With a usually used chip rate of 2.5 MHz, thenominal precision of a conventional TWSTFT equals to 0.5 ns. The usage of DPN (dual pseudorandom
noise) signals is equivalent to increase the chip rate. In this method two separated narrow band signals
work like a signal with a chip rate which is equal to the band separation. We used two 127.75-kHz
signals with a frequency separation of 20 MHz and achieved a measurement precision of 30 ps1.
Additionally, narrower band signals allowed us to decrease the rental fee on the satellite transponder.

Modified Allan deviation

For further precision improvement, we started the
0-km, common clock
development of carrier phase two-way satellite
100-km, H-maser comparison-13frequency transfer. This concept was first10
1000-km, H-maser comparison
2
demonstrated by Fonville et al . We succeeded to-14
10
establish an operational link for the first time. The
phase jitter from the onboard oscillator and-15
10
Doppler effects due to the satellite motion are
removed by using four phase measurements
-16
10
0
1
2
3
4
5
6
10
10
10
10
10
10
10
performed between two ground stations. In a
Averaging time [s]common clock measurement on a zero baseline we Fig. 87: Transfer stability for different baseline
obtained a precision of 0.2 ps. As a next step, a lengths. The bump in the black curve is caused byhydrogen maser comparison was performed on a indoor temperature variation.
100-km baseline3. The result was compared withthat of GPS carrier phase measurement and agreed on the 10-16 level. At present, measurements on a
1000-km baseline are ongoing. As shown in Fig. 1, a baseline length dependency for both short and longterm stabilities could not be seen. However, more detailed study will be required, especially on theeffects caused by the ionosphere. Our presentation will discuss recent results.

IFCS-EFTF5-E2-2

TWSTFT Calibration Involving Four Sites Using a
Mobile Station on a Trailer
Thorsten Feldmann1, Arvind Balu1, Shuo Liu1, Wolfgang Schäfer1, Andreas Bauch2,
Jürgen Becker2, Dirk Piester2, Joseph Achkar3, Amale Kanj3,*, Christian Schlunegger4
1

2

TimeTech GmbH, Stuttgart, Germany
Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig,
Germany
3
Observatoire de Paris (OP/LNE-SYRTE), Paris, France
4
Federal Institute of Metrology (METAS), Bern-Wabern, Switzerland
Email: info@timetech.deCalibrated time transfer between two remote locations using the Two-Way Satellite Time and Frequency
Transfer (TWSTFT) technique with telecommunication satellites requires the accurate knowledge of theinternal delays of the equipment involved, the asymmetry between signal paths, and the delays of theconnections of the equipment to local time scales. In case of a single satellite transponder used for bothsignal paths, these delays depend only on the ground equipment, because free space and atmosphericinduced delays cancel out in the two-way combination. A single transponder also enables time transfer
between two stations located at the same site. The traveling station is operated together with the fixed
equipment at each site in a common-clock setup for some days. For each pair of ground sites thedifferences between the common-clock data reflect the delays of the fixed stations, while ideally thedelays associated with the traveling equipment cancel out.
In November 2012 the time transfer links between Physikalisch-Technische Bundesanstalt (PTB),
Observatoire de Paris (OP/LNE-SYRTE), Swiss Federal Institute of Metrology (METAS), and
TimeTech GmbH were calibrated using TimeTech’s mobile TWSTFT calibration station assembled on a
trailer.
The calibration trailer was firstly introduced at EFTF 2012282. Its stability during the initial calibration
campaign was verified by taking common-clock data at TimeTech before and after the trip to themetrology laboratories, and by triangle closures, which are based on the principle that the sum ofcalibrated links between three sites should be zero within the combined uncertainty.
We report on the current status of the calibration station and present the results of the calibration
campaign, the uncertainty estimation, and comparisons to previous calibrations. Since the mobile station
allows for a standardized and easily executable procedure at each laboratory, the systematic
uncertainties are significantly below one nanosecond.

*

Present address: Bureau International des Poids et Mesures (BIPM), Pavillon de Breteuil, F-92312 Sèvres Cedex, France.

282

T. Feldmann, A. Balu, C. Molard, W. Schäfer, D. Piester, “State-of-the-Art Time Link Calibration with a mobile
TWSTFT Station”, Proc. EFTF, Gothenburg, Sweden, April 24-26, 2012.

IFCS-EFTF5-E2-3

Simulation Study for Commercial Time Transfer Service over
Geostationary Satellite
Jacqueline Walker1, Marco Genova2
1

Department of Electronic and Computer Engineering, University of Limerick, Limerick, Ireland
2
Mixed Processing Ltd, Office 301, Shannon Airport House, Shannon, Ireland
Email: jacqueline.walker@ul.ie

Over the last twenty years, many technologies and services have come to rely on the GPS for precise
timing. However, concern is increasing about the wisdom of being reliant on a single timing solution283
provided by a single country and because of the susceptibility of the GPS signal to unintentional
interference, jamming and spoofing. There are several projects underway to develop similar systems,
e.g. Galileo, or upgrade existing ones, e.g. GLONASS. There are also other approaches to timingtransfer available: over optical media, using high power LF signals and over commercial satellite links.
Timing transfer over optical media shows promising performance but requires the installation of a
dedicated network infrastructure. High power, low frequency radio signals are an established solution
but cannot easily cover such a wide geographical area as a satellite solution. Timing transfer overgeostationary satellite has been pursued since the start of the satellite era 284, but a commercial timing
service product of this kind is not yet available.
In the paper, we report on further development of our system for timing signal transfer from a precisionreference clock using commercial satellite links285. The system will use the projected ephemeris
information provided by the satellite operator and, with a set of master stations tracking the satellite
position and using TWTFT measurements to synchronize their clocks, data transmitted with thereference timing signal will allow slave stations to adjust the timing signal, compensating for thesatellite motion and other uncertainties in the path delay. Using projected ephemeris data and comparingthat data in real time with measurements which themselves are affected by other sources of delay is achallenging task when the goal is timing signal transfer with no more than 100 ns of jitter peak-to-peakat the receiving stations. Analysis has focused on quantifying the impact of errors in satellite ranging on
the satellite position calculation. Numerical evaluation of the error expressions suggests that range errors
would have to be less than 50 m to achieve the desired performance.
We will report on a simulation of the full system implementation with three master stations, including
models for the master station clocks and TWTT measurements, using a Kalman filter to track thesatellite position. The Kalman filter has been developed in the ECEF co-ordinate frame and uses realworld archived satellite ephemeris data as the ground truth for the simulation incorporating models for
extraneous delays such as atmospheric effects. Preliminary results from the simulation suggest that therange error goal could be met and results will be presented of a simulation study of the relationshipbetween range measurement error and timing signal transfer performance.

283

M. A. Lombardi, “Microsecond accuracy at multiple sites: is it possible without GPS?” IEEE. Instrum. Meas. Mag., vol.
15, no. 5, p. 14-21, 2012.
284

D. W. Hanson and W. F. Hamilton, “One-way time synchronization via geostationary satellites at UHF,” IEEE T.
Instrum., vol. 20, no. 3, pp. 147-153, 1971.
285

J. Walker and M. Genova, “Experimental and Simulation Study for Commercial Time Transfer Service over
Geostationary Satellite”, Proc. 44th PTTI Meeting, pp. 221-237, 2012.

IFCS-EFTF5-E2-4

Time Service through BD GEO Satellites
YUAN Haibo1,3, YANG Fan1,2,3, GUANG Wei1,31Natioanl Time Service center,CAS, Xi’an China
University of Chinese Academy of Sciences, Beijing, China
3
Key Laboratory of Time & Frequency Primary Standard, CAS, Xi’an China
2

Email: yuanhb@ntsc.ac.cn
The Space segment of BeiDou(Compass) global navigation satellite system consists of the 5 Group On
Earth Observations (GEO) satellites and 30 Non-GEO satellites(Medium Earth Orbit (MEO) satellites
and Inclined Geo Stationary Earth Orbit (IGSO) satellites). At present the Beidou system has begun toregional services based on the GEO satellites and the IGSO satellites. The range of services is covering
China and neighboring countries and area. There are 5 GEO satellites on orbit. Users can receive the
BeiDou system time which is steered to the UTC through the UTC(NTSC) by GNSS CV and TWSTFT.
The time service performance of the BeiDou system is concerned by the time users. In this paper, theBeiDou system is introduced firstly, then the satellite time service and the data processing methods areanalyzed, based on the analysis, the time service performance of the 5 GEO satellites is discussed, andthe results show that Eliminating the ionospheric delay and reducing the impact of the troposphere andrelativistic effects, the time service performance of the 5 GEO satellites are all stable and their accuracy
is quite close to 10ns which can meet the needs of the vast majority of high-precision time users. Fig 1 isthe result of the BDT-UTC(NTSC) by GEO5 between MJD 56293 and 56323.

Fig 1. Performance of Beidou single satellite(GEO5) time service.
The reference of BDT is UTC(NTSC) which is kept by Naional Time
Service Center, Chinese Academy of Sciences.

IFCS-EFTF5-E2-5

Review of Two-way Satellite Time and Frequency Transfer for
UTC and TAI generation
Z. Jiang, H. Konaté and W. Lewandowski
Time Department, Bureau International des Poids et Mesures (BIPM)
Pavillon de Breteuil F-92312, SÈVRES CEDEX, France
zjiang@bipm.org
The initial studies of time transfer through geostationary communication satellites started in the 1962
using the Telstar satellite. Earlier experiments continued with a number of other carriers. The techniqueof Two-Way Satellite Time and Frequency Transfer (TWSTFT) 286 started its experimental steps earlier
than GNSS as a promising tool for accurate time and frequency transfer.
The Consultative Committee for the Definition of the Second (CCDS, at present Consultative
Committee for Time and Frequency, CCTF) made a declaration in 1989 to encourage the use of
TWSTFT and suggested the International Bureau of Weights and Measures (BIPM) to create a working
group on TWSTFT. In 1992, several commercial satellite systems were available, and modems adapted
for the technique were commercialized. Some ten UTC laboratories were equipped with different typesof modems and other facilities for the clock comparisons with TWSTFT. On the other hand theInternational Telecommunication Union (ITU) approved in 1995 a recommendation fixing the standard
data format for the TWSTFT operations.
The first TWSTFT link introduced in the UTC computation was between TUG in Austria and the PTB,
and was published in the BIPM Circular T for July 1999. Inter-continental TWSTFT links between
Europe, America and Asia were then established, as well as the continental links. TWSTFT becomecomplementary to the already in use GPS time transfer. It presented the advantage of being independent
from GPS, thus enhancing the robustness of the system of time links for UTC/TAI. The accuracy of
TWSTFT rapidly proved to be better than that of GPS time transfer and this is still the case today.
Meanwhile, since recent years the noise of GPS time transfer, represented by the type A uncertainty uA,dramatically decreased with the use of GPSPPP for the UTC/TAI routine computations. From 2011 the
combination of TWSTFT and GPSPPP is used for computing time links for UTC/TAI to take theadvantages of both techniques.
In addition to its contribution to the computation of UTC/TAI, TWSTFT has also served to thevalidation of the GNSS techniques and methods incorporated in the past 10 years; examples are theGPS all in view, the GPSP3, the GPSPPP and the implementation of clock comparisons using
GLONASS. This paper reviews fourteen years of contribution of TWSTFT to the maintenance of UTC
and discusses its future developments, such as the use of the TWSTFT carrier phase and DPN. It also
intends to render tribute to the pioneers of the TWSTFT.
Key words: UTC and TAI, Time and frequency transfers, TWSTFT

286

In the earlier documents, the term TWSTT (Two-Way Satellite Time Transfer) was used.

Temperature Stabilization for MEMSCLUB D
Tuesday, July 23 2013, 02:00 pm - 03:30 pm
Chair:Jan Kuypers
Sands 9, Inc.

IFCS-EFTF1-E3-1

We Know That MEMS is Replacing Quartz.
But Why? And Why Now?
Aaron Partridge
SiTime Corp., Sunnyvale, CA/USA
Email: ap@sitime.com
MEMS-based oscillators were first produced commercially six years ago. Now MEMS is making
significant incursions into what was once the exclusive territory of quartz. By the time this paper isdelivered in July 2013, over 200M MEMS oscillators will have been shipped, with over 100M units
expected to ship in 2013, at a growth rate of about 70% per year.
There are five fundamental drivers for the transition from quartz to MEMS: (1) Basic MEMS oscillators
are maturing with decreasing phase-noise and decreasing power consumption in smaller packages, andwith these improvements they are reaching further into common quartz applications. (2) Specialized
MEMS oscillators are transitioning new markets, for example in applications requiring ultra-low power,
sub-ppm precision, high frequency differential signaling, sub-picosecond integrated jitter, voltage
control, digital control, spread, and output edge-rate control. (3) MEMS oscillators have shown higher
reliability and lower failure rates than quartz oscillators. (4) MEMS oscillators have demonstrated lower
electromagnetic, vibration, and acceleration sensitivity than quartz oscillators. (5) MEMS oscillators sell
at lower price points than the quartz parts they replace.
Why is this transition happening now, rather than ten years ago or ten years from now? One answer isthat the transition has been paced by the MEMS community developing the necessary high stability,
high frequency, high Q, and high output resonators. A second answer is that MEMS oscillators rely on
advanced circuit architectures, particularly leveraging fractional-PLLs and precision temperature
sensors. And these specialized circuits have only recently become sufficiently small, low noise, power
efficient, and accurate.
Looking forward, the depth and breadth of the applications served by MEMS oscillators will continue toexpand, while the drivers favoring MEMS oscillators will further accelerate their adoption.

IFCS-EFTF1-E3-2

Lisha Shi1, Gianluca Piazza2
1
Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA, 2Department ofElectrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, USA

Ion-Sliced Lithium Niobate on Silicon Dioxide for Engineering theTemperature Coefficient of Frequency of Laterally Vibrating Resonators
Lisha Shi, Gianluca Piazza
Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
Email: lishashi@andrew.cmu.edu, piazza@ece.cmu.edu
This paper reports, for the first time, on the demonstration of Laterally Vibrating Resonators (LVRs)
based on Y-cut Ion-Sliced Lithium Niobate (LN) thin films on silicon dioxide (SiO 2) (Fig.1a-b). By
adding a thermally grown layer of SiO2 to the resonator stack, it is possible to engineer the temperature
coefficient of the resonator and therefore ensure the use of these devices for applications where tighttemperature specifications are required.
Prior demonstrations of LN LVRs 287, 2
have shown the capability of attaininga high Kt2 (> 20%) and Qs of about
1,000, but exhibited a rather large andnegative temperature coefficient of
frequency (TCF) of about - 80 ppm/°C.
Furthermore, they were built on a LN
substrate with either BCB or SiO2 as
sacrificial layers, which required a wet
etch step for the release of theresonator. In this work, the LN LVR isbuilt on top of a SiO2 layer andreleased from the underlying siliconwafer by dry etching in XeF2. With the Fig.1 (a) Mock-up view of LiNbO3-on SiO2 MEMS microhLN set at 420nm and hSiO2 at 1600nm, resonator (b) Optical image of a 511.8MHz LN LVR. The
this first demonstration (Fig.1b) period of the interdigitated finger was set to be 6 μm withyielded TCF of + 11ppm/°C, + each metal line having a width of 2μm (c) The comparison
18ppm/°C and + 20.4ppm/°C forof the averaged measured and simulated Kt2 for LN on
devices respectively oriented at 80˚, SiO LVRs for various orientations. (d)The measured and250˚, and 20˚ to the x-axis. The positive
fitted admittance response of LN on SiO2 LVRs with Qs in
TCF clearly indicates the effect of theexcess of 1,300 in air
SiO2, matches with FEM simulations, and offers evidence that TCF engineering is possible. Most
importantly, these LN LVRs still exhibited high values of the electromechanical coupling, Kt2, around
6.2% (see Fig.1c) and Qs in excess of 1,300 in air at 419.3 MHz (Fig.1d). By optimizing the relativevalues of hLN and hSiO2 it is ultimately possible to attain devices with zero first order TCF.

1
2

2

R.Wang, S. Bhave, and K. Bhattacharjee “High Kt ×Q, Multi-frequency Lithium Niobate Resonators” MEMS 2013(2013)

S. Gong, L. Shi, G. Piazza, “High electromechanical coupling MEMS resonators at 530 MHz using ion sliced x-cut
LiNbO3 thin film”, International Microwave Symposium (2012).

IFCS-EFTF1-E3-3

Experimental determination of the temperature dependency ofelastic constants of degenerately n-doped silicon
Antti Jaakkola, Mika Prunnila, Tuomas Pensala, Panu Pekko, James Dekker
VTT Technical Research Centre of Finland, Espoo, Finland
Email: antti.jaakkola@vtt.fi
Degenerate doping of silicon has recently been found as an attractive method of passive temperaturecompensation in MEMS resonators, and it has been shown that with n-type doping one can change thetypical silicon resonator TCF of about -30 ppm/K to zero, or even to positive values [1]. To optimize
the temperature stability of a resonator, adesigner needs to know the thermal
dependencies of the elastic parameters c11,
c12
and
c44.
However,
published
experimental material data has been scarceand limited to a maximum dopant
concentration of n=2×1019cm-3 [2]. In thiswork we determine silicon elastic
parameters for five different n-dopant
concentrations in the range of n = 1.7 …
7.0×1019cm-3.
Extraction of the elastic parameters is basedon the measurement of the resonancefrequencies of electrostatically coupled bulk
mode MEMS resonators as a function oftemperature. The devices were fabricated on(100) SOI wafers. The set of resonators Fig. 88: Temperature dependence of the shear constant c11consists of two Lamé mode resonators c12 for different dopant concentrations. Data with lowestaligned with 100 and 110 crystal directions, two dopant concentrations is from arsenic doped wafers;
and five length extensional beam resonators phosphorus is the dopant for the remaining cases.
spanning directions from 100 to 110. Since
the functional dependency of the modal frequencies on the elastic parameters varies among theresonators, one can extract the elastic parameters from the frequency data.
We present the method of elastic parameter extraction, and show full experimental results for elastic
parameters c11, c12 and c44. The temperature behavior of the shear constant c11-c12 is shown in Fig. 1 fordifferent dopant concentrations as an exemplary illustration of the data set. Reliability of the obtained
results is discussed.
[1] T. Pensala, A. Jaakkola, M. Prunnila, J. Dekker, “Temperature compensation of silicon MEMS
resonators by heavy p and n type doping”, IEEE International Ultrasonics Symposium, Orlando, FL,
Oct. 2011, pp. 1952-1955.
[2] J.J. Hall, “Electronic Effects in the Elastic Constants of n-Type Silicon”, Physical Review, vol. 161,
no. 3, 1967, pp. 756-761.

IFCS-EFTF1-E3-4

Temperature Dependence of the Elastic Constants ofDegenerately Doped Single Crystal Silicon
Eldwin J. Ng1, Chae Hyuck Ahn1, Yushi Yang1, Vu A. Hong1, Thomas W. Kenny1
1

Department of Mechanical Engineering, Stanford University, Stanford, California, USA
Email: eldwin@stanford.edu

Degenerate doping in silicon has been recently demonstrated to reduce the frequency-temperaturedependence of MEMS resonators288. Doping induces a strain in the silicon crystal and causes a shift in theelectronic band structure, which in turn affects the elastic properties of the material2. For monocrystalline
silicon (an orthotropic material), the elastic properties3 are characterized by c11, c12, c44. Empiricaltemperature dependences of the elastic constants (Tc11, Tc12, Tc44) can be extracted using at least threedifferent resonators, as performed by Bourgeois for lightly doped silicon4: firstly, finite element analysis(FEA) is used to model the frequency dependence on the elastic constants for each resonator; next,
frequency-temperature dependences are measured for fabricated resonators; putting these two pieces
together, the temperature dependence of elastic constants can be extracted (Fig. 1). Double-ended tuning
forks (DETF), breathe-mode double rings, and wineglass (second mode) disk resonator gyroscopes (DRG)
were fabricated and encapsulated with epitaxial polysilicon in an ultra-clean environment free ofcontamination and native oxide. Frequency-temperature curves were measured for these resonators (Fig. 2),
and the extracted temperature dependences of the elastic constants are listed in Table 1.
With the extracted material constants and FEA, the method can be reversed to predict the frequency-

Fig. 89: Method used to extract
the temperature dependence ofthe elastic constants.

Fig. 2: Frequency-temperature dependences of various resonators
fabricated with 8e19 cm-3 phosphorus-doped single crystal silicon.
temperature dependence of any
acoustic silicon resonator with the given doping. For validation,
predicted and experimental values of the frequency-temperaturedependence of the third resonant mode of the DRG (not used in theextraction) are compared (Fig. 3).

Table 1. First-order dependence of the elastic constants on
temperature, extracted from experimental data and FEA models.
Dopant, Concentration
Boron, 1e20 cm-3
Phosphorus, 8e19 cm-3

Tc11
(ppm/°C)
-70.1
-45.1

Tc12
(ppm/°C)-140.1-181.4

Tc44(ppm/°C)
+14.9
-65.1

Fig. 3: f-T prediction comparedagainst experimental data for the
DRG’s third resonant mode using
the extracted values.

This work was supported by the DARPA PNT program, managed by Dr. Andrei Shkel, contract #N66001-12-1-4260.
1
3
A.K. Samarao, Trans. Elect. Dev. 59 (1), 2012.
M. Hopcroft, J. MEMS 19 (2), pp. 229-238, 2010.
2
4
R.W. Keyes, Solid State Physics 20, pp. 37-90, 1968.
C. Bourgeois, Freq. Ctrl. Symp., pp. 791-799, 1997.

IFCS-EFTF1-E3-5

A Piezoresistive CMOS-MEMS Resonator with High Q and Low TCf
Cheng-Syun Li1, M.-H. Li1, C.-H. Chin1, C.-Y. Chen1, Philip X.-L. Feng2, and S.-S. Li1
1Nat. Tsing Hua Univ., Hsinchu, Taiwan, and 2Case Western Reserve Univ., OH, USA

Email: s9835815@m98.nthu.edu.tw
Combining merits of quality (Q) factor greater than 15,000, temperature coefficient of frequency (TCf)around -12.5ppm/°C, and operating power lower than 400W all in a single device, a high frequency
CMOS-MEMS bulk-mode resonator is demonstrated here via differential piezoresistive transduction289.
This makes an excellent candidate for timing reference and frequency control applications. To attain thehighest Q among reported CMOS-MEMS resonators, a dog-bone design (Fig.1a) has been adopted via
two bulk-mode longitudinal vibrating beams which consist of only low-loss materials (i.e., poly-Si andSiO2) from a standard 0.35m 2P4M CMOS technology. To achieve the better temperature stability ascompared with those of other CMOS-MEMS resonators, a constant-resistance control approach290 was
implemented to enable an ovenized resonant element where the poly-Si heater and thermometer wereboth embedded inside the resonator structure, hence providing excellent thermal isolation, localized
heating capability, and on-site/real-time temperature measurement. With much higher gauge factor andresistivity than that in our previous design1, a poly-Si layer originally used for CMOS resistors was
purposely chosen to serve as a piezoresistor for motion detection, thus exhibiting decent performance
under sub-mW operation. This technology is expected to pave the way for future single-chip oscillatorswith low power, high performance, and excellent thermal stability.
Fig.1a presents an optical micrograph of the fabricated resonator, showing its dog-bone structure withembedded electrodes (yellow) and piezoresistors (blue and pink) since the high-Q structural material(SiO2) is transparent to visible light. With the differential piezoresistive transduction1 to reduce thefeedthrough, Fig.1b presents the measured frequency characteristics with clear resonance behavior underpoly1 (original gate poly-Si) and poly2 (original resistor poly-Si) detections, both of which show Q >15,000 and more than 20dB stopband rejection. It is worth noting that the poly2 sensing scheme
indicates a low-power operation (only 363W) and high electromechanical coupling coefficient due to
its larger gauge factor than that of the poly1 scheme. Fig.1c presents the measured thermal stability
using constant-current (CC), constant-voltage (CV), and constant-resistance (CR) controls of thepiezoresistor (poly1), demonstrating the lowest TCf to date in CMOS-MEMS resonators under the CR
approach2.
Bias-Tee

Id

Port 1

vi

VP

im1

VP =75 V(a)Port 3

Bias-Tee

vi

4000
3000

-80
-90

-100

im2

Port 1

fo ~ 5MHz

Poly2 Sensing:-70 0.25mA/0.363mW

-60

Poly2
Poly1

Poly1 Sensing:
2mA/1.160mW

Q > 15,000-110
0.999 0.9995
1
1.0005 1.001
Normalized Freq. [MHz/MHz](b)

 f/fo [ppm]

VD

Transmission [dB]

Port 2

CC
CV
CR

2000

y = 35.026x + 148.37
R² = 0.9783
y = 32.964x + 127.4
R² = 0.9929

1000

0

-1000

y = -12.533x - 87.541
R² = 0.9907

-2000
0

(c)

20

40

60

80

Temperature [°C]Fig. 1: (a) Schematic and OM views, (b) measured frequency response, and (c) measured thermal
stability of the CMOS-MEMS bulk-mode resonator under differential piezoresistive transduction.

289

C,-S. Li, et al., “Capacitively-driven and piezoresistively-sensed ….,” MEMS’12, Paris, France, pp.539-542, 2012.

290

C.-C. Chen, et al., “Enhancement of temperature stability via …,” MEMS’13, Taipei, Taiwan, pp.765-768 , 2013.

Ion Clocks
CLUB H
Tuesday, July 23 2013, 04:30 pm - 06:00 pm
Chair:

Scott Diddams
NIST

IFCS-EFTF6-F1-1

Yb+ Single-Ion Optical Frequency Standard with Systematic
Uncertainty at the 10-17 Level
N. Huntemann, B. Lipphardt, Chr. Sanner, M. V. Okhapkin, Chr. Tamm, E. Peik
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
Email: ekkehard.peik@ptb.de

The electric octupole transition 2S1/2(F = 0)→2F7/2(F = 3,mF = 0) of the 171Yb+ ion at 467 nm with anatural linewidth in the nHz range possesses a low sensitivity to frequency shifts induced by static
electric or magnetic fields291. Because of the extremely small oscillator strength of the transition, its
excitation requires high spectral power density. The required intensity introduces a significant light shiftof the transition frequency. With a real-time extrapolation scheme that eliminates this shift, theunperturbed transition frequency has been realized with a fractional uncertainty of 7.1×10 -17 and thefrequency was measured as 642 121 496 772 645.15(52) Hz1, where the uncertainty was dominated by
the systematic uncertainty of the caesium fountain clock. Recently, we have implemented the HyperRamsey excitation scheme (HRS)292 with a pulse sequence that is tailored to produce a resonance signalthat is immune to the light shift induced by the probe laser. In the HRS scheme, the effect of the lightshift on the spectrum is compensated by introducing a frequency step of the probe light during theinterrogation pulses. The experiments demonstrate a suppression of the light shift by four orders ofmagnitude and an immunity against its fluctuations293.
For the operation as a frequency standard, a servo scheme using HRS is combined with an interleaved
servo using Rabi excitation with the same probe light intensity. The frequency offset between the Rabiand HRS interrogations is taken to control the light shift compensating frequency step in the HRS. This
ensures that slow variations of the light shift will not degrade its suppression. This method was appliedin frequency comparisons between the 171Yb+ single-ion clock and the Sr lattice clock of PTB. It has
allowed us to perform a more precise measurement of the static quadratic Stark shift of the 2S1/2→2F7/2transition. Together with improved knowledge of the thermal radiation emitted by the ion trap and its
mounting structure, this will reduce the systematic uncertainty contribution of the Stark shift induced byblackbody radiation, which presently dominates the uncertainty budget.
This work is partly funded by the EMRP project SIB04 Ion Clock. The EMRP is jointly funded by
the EMRP participating countries within EURAMET and the European Union.

291

N. Huntemann, M. Okhapkin, B. Lipphardt, S. Weyers, Chr. Tamm, and E. Peik, “High-Accuracy Optical Clock Basedon the Octupole Transition in 171Yb+”, Phys. Rev. Lett. 108, 090801 (2012).
292
V. I. Yudin, A. V. Taichenachev, C. W. Oates, Z. W. Barber, N. D. Lemke, A. D. Ludlow, U. Sterr, Ch. Lisdat, and F.
Riehle, „Hyper-Ramsey spectroscopy of optical clock transitions”, Phys. Rev. A 82, 011804(R) (2010).
293
N. Huntemann, B. Lipphardt, M. Okhapkin, Chr. Tamm, E. Peik A.V. Taichenachev and V. I. Yudin,“Generalized Ramsey Excitation Scheme with Suppressed Light Shift”, Phys. Rev. Lett. 109, 213002 (2012).

IFCS-EFTF6-F1-2

Control of the systematic shifts of the 88Sr+ single-ion opticalfrequency standard at 2 parts in 1017
Pierre Dubé, Alan A. Madej, and John E. Bernard
National Research Council of Canada, Ottawa, ON, Canada K1A 0R6
Email: pierre.dube@nrc-cnrc.gc.ca

Recently, our group has reported an evaluation of the systematic shifts on the 88Sr+ ion clock transition
frequency at the 2.3×10-17 level,294 an order of magnitude lower than that of state-of-the-art cesium
fountain atomic clocks.295 This low uncertainty was achieved using a number of methods employed tomeasure, reduce, and even cancel the most important shifts that are known to affect the 5s 2S1/2-4d 2D5/2
clock transition frequency of the 88Sr+ ion.
In our experiments, the center frequency of the S-D transition is determined by taking the averagefrequency of three pairs of symmetric Zeeman components specially chosen to connect to all the upper
state sublevels. This effectively averages over the energies of the 2D5/2 sublevels with the important
benefit of a very high cancellation level of the electric quadrupole shift (EQS).296 The uncertainty on thecanceled EQS is estimated at  3×10-19 in our system.297 In addition, this method cancels the tensor partof the Stark shift caused by micromotion and other sources.
The ion micromotion at the trap frequency causes second-order Doppler and Stark shifts. These shifts
are reduced to a level of 2.2×10-17 after minimization of micromotion along three mutually orthogonal
directions. An additional suppression of these shifts is obtained by observing that the scalar Stark andsecond-order Doppler shifts have opposite signs for the 88Sr+ ion and that they cancel each other when
the trap is operated at a frequency of 14.39(25) MHz.297 The suppression factor obtained is 28,
determined by the uncertainty on the differential scalar polarizability of the S-D transition.298 After
minimization and with the trap operated at the special frequency, the uncertainty on the micromotion
shifts is 1×10-18.
The blackbody radiation (BBR) shift uncertainty was estimated using measurements of the endcap trap
electrode temperatures and a model to determine the field at the ion. The estimated uncertainty is
2.2×10-17, primarily from that of the differential scalar polarizability.297 The BBR shift is currently thelargest source of uncertainty for the 88Sr+ ion optical frequency standard. A detailed analysis of thesystematic shifts affecting the 88Sr+ S-D frequency297 indicates that the total uncertainty is 2.3×10-17.
We have also reported recently a measurement of the 88Sr+ S-D frequency made over a 2-month period
by comparison with a maser referenced to the SI second.294 The frequency measured is444779044095485.5(9) Hz, with an uncertainty determined by the evaluation of the maser which had
a fractional frequency uncertainty of 2×10-15. The measured value was recommended by theConsultative Committee for Time and Frequency (CCTF) for an update of the 5s2S1/2-4d2D5/2 transition
frequency of 88Sr+ which is used as a secondary representation of the second.

294

A. A. Madej, P. Dubé, Z. Zhou, J. E. Bernard, and M. Gertsvolf, Phys. Rev. Lett. 109, 203002, 2012.
J. Guéna et al., IEEE Trans. Ultrason. Ferroelectr. Freq. Control 59, 391, 2012.
296
P. Dubé, A.A. Madej, J.E. Bernard, L. Marmet, J.S. Boulanger, and S. Cundy, Phys. Rev. Lett. 95, 033001, 2005.
297
P. Dubé, A.A. Madej, Z. Zhou, and J.E. Bernard, Phys. Rev. A 87, 023806, 2013.
298
D. Jiang, B. Arora, M.S. Safronova, and C.W. Clark, J. Phys. B 42, 154020, 2009.
295

IFCS-EFTF6-F1-3

Measurement of the optical frequency ratio between two clocktransitions in a single ion of 171Yb+
Steven King, Rachel Godun, Peter Nisbet-Jones, Helen Margolis, Luke Johnson and Patrick Gill
National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
Email: steven.king@npl.co.uk
Singly-ionised ytterbium-171 has two clock transitions that are currently under investigation as
candidates for the redefinition of the SI second. In particular, the 2S1/2 – 2F7/2 electric octupole transition
has shown great promise. Two recent absolute frequency measurements of this transition at NPL299 andPTB300 are in good agreement, which demonstrates that this transition has potential to realise a
reproducible optical frequency standard despite the previously limiting ac Stark shift that arises from therelatively high probe laser intensities required to drive a transition with a natural linewidth on the orderof nanohertz.
In addition to its use as an optical frequency standard, this system also offers the intriguing possibilityof measuring any present-day time-variation of the fine structure constant, α. By repeatedly measuring
an optical frequency ratio between the electric octupole transition at 642 THz and the 2S1/2 – 2D3/2
electric quadrupole transition at 688 THz, any variation in α is amplified301 by nearly a factor of 7.
We will present our results from our first measurements of this optical frequency ratio. Two probe
lasers are stabilized to high-finesse optical cavities with resulting fractional short-term instabilities near
1×10-15, and are then further stabilized to their respective atomic transitions in a single ion in aninterleaved manner. An optical frequency comb is then able to measure the ratio between the opticalfrequencies of these two stabilized lasers in real-time. We will discuss the various challenges that arise
from a measurement performed in this manner, and in particular we will discuss the compromises thathave to be made between various systematic shifts. Recent experimental upgrades will also be presented
including a new, more reliable probe laser to drive the electric quadrupole transition, a distributed
feedback diode (DFB) repumper laser to clear out the extremely long-lived 2F7/2 level, and the successful
implementation of automatic re-locking of many of the lasers in the experiment. We will also present theresults of ongoing improvements that will reduce the systematic uncertainties associated with future
measurements.

299

S. A. King et al., “Absolute frequency measurement of the 2S1/2 – 2F7/2 electric octupole transition in a single ion of 171Yb+
with 10−15 fractional uncertainty”, New J. Phys., vol. 14, 013045, 2012
300

N. Huntemann et al., “High-accuracy optical clock based on the octupole transition in 171Yb+”, Phys. Rev. Lett., vol. 108,090801, 2012
301

S. N. Lea, “Limits to time variation of fundamental constants from comparisons of atomic frequency standards”, Rep.
Prog. Phys., vol. 70, p1473, 2007

IFCS-EFTF6-F1-4

The Optical Frequency Standard of Trapped and Cold 40Ca+
H. Guan, 1, 2 Y. Huang, 1, .2 J. Cao, 1, 2 P. Liu, 1, 2 X. Huang, 1, 2 and K. Gao1, 2, *1
2State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics

Key Laboratory of Atomic Frequency Standards,Wuhan Institute of Physics and Mathematics, Chinese
Academy of Sciences, Wuhan 430071, China*Email: klgao@wipm.ac.cnxv

Progress on the development of the optical frequency standard based on single-trapped 40Ca+ with a“clock” transition at 729 nm is described. A single Ca ion was trapped and laser cooled in a miniaturePaul trap. The commercial Ti:sapphire laser systems at 729 nm were referenced respectively to thesuper cavities to meet the requirements of probing 4s 2S1/2-3d 2D5/2 clock transition with ultra narrow
linewidth. The 729 nm laser was locked to the clock transition by four points locking scheme. The
overall systematic uncertainty of the 4s 2S1/2-3d 2D5/2 clock resonance has been characterized to be at
10−16 level [1-2]. The absolute frequency of the clock transition is measured based on the GPS system. In
our measurement, an optical frequency comb is referenced to a Hydrogen maser, which is calibrated to
the SI second through the Global Positioning System (GPS). Using the GPS satellites as a link, we canmeasure the frequency difference of the two Hydrogen masers with a long distance, one in WIPM
(Wuhan) and another in NIM (Beijing). The frequency difference of the Hydrogen maser in NIM(Beijing) and the SI second calculated by BIPM is published on the BIPM website every 1 month, with atime interval of every 5 days. By analyzing the experimental data obtained with a total averaging time of> 2×106 s within 32 days, the absolute frequency of the 40Ca+ 4s 2S1/2–3d 2D5/2 clock transition ismeasured as 411 042 129 776 393.0 (1.6) Hz with a fractional uncertainty of 3.9×10 -15[2], which isadopted by the Consultative Committee for Time and Frequency conference (CCTF 19) in 2012.

IFCS-EFTF6-F1-5

Direct frequency comparison between a single Ca+ clock
and a Sr lattice clock
Kensuke Matsubara1, Hidekazu Hachisu1, Shigeo Nagano1, Ying Li1, Asahiko Nogami1,
Clayton Locke1, Kazuhiro Hayasaka1, Mizuhiko Hosokawa1, Tetsuya Ido1,2
1Space-time standards laboratory, NICT, Tokyo, Japan, 2JST-CREST, Tokyo, Japan
Email: ido@nict.go.jp

Comparison between independent frequency standards is the most reliable means to evaluate theirreproducibility and stability. Optical frequency standards have a strong advantage in the speed of thiscomparison process, requiring less than 1,000 seconds to evaluate a fractional frequency difference atthe 10-16 level of uncertainty. In contrast, state-of-the-art Cs fountain clocks operating in the microwave
regime require more than six hours of integration time302. Optical frequency combs can be used tomeasure a frequency ratio as well as relative instability of optical clocks. Such a frequency ratio isequivalent to a measurement based on not the SI second but an optical frequency standard. Hence,
precision measurements of frequency ratios are lately encouraged to support and confirm the validity ofthe metrology based on optical frequency standards. Frequency ratios can be also used in searches for
temporal variation of fundamental constants303.
We report frequency comparison of a 40Ca+ 2S1/2-2D5/2 with an 87Sr 1S0-3P0 lattice clock transition. The
accuracy and the instability of the 87Sr clock at NICT have been previously confirmed to be at the 10-16level304 and the absolute frequency of the Sr clock is
consistent with those of other laboratories305. We
therefore characterized the Ca+ clock by comparison
with the Sr clock. The frequency ratio measurement has
shown that the fractional instability of the Ca+ clock
reaches parts in 10-16 in less than 1,000 s (see Fig. 1),
with long term stability characterized as () = 2.4 ×
10-14 / 1/2, consistent with the quantum projection noise
limit derived from the Fourier limited spectral width of
26 Hz of the Ca+ clock. Taking systematic uncertainties
into consideration, the frequency ratio f(Ca+) / f(Sr) is
determined with uncertainty of 2.3 × 10-15, in Fig. 90: Instability of the frequency ratio (red),agreement with independent absolute frequency limited by the instability of the Ca+ clock. An
measurements306 of 40Ca+ based on TAI link.
interleaved measurement of the Sr clock
indicates the instability shown by a black line.
302

J. Guena, et al., “Progress in atomic fountains at LNE-SYRTE” IEEE Transactions on Ultrasonics, Ferroelectrics andFrequency Control, vol. 59, p. 391-420, 2012.
303

J.-P. Uzan, “The fundamental constants and their variation: observational and theoretical status”, Rev. Mod. Phys. vol. 75
p. 403-455, 2003.
304

A. Yamaguchi, et al., “Direct comparison of distant optical lattice clocks at the 10-16 uncertainty”, Appl. Phys. Express
vol. 4 082203, 2011.
305

A. Yamaguchi, et al., “Stability transfer between two clock lasers operating at different wavelengths for absolute
frequency measurement of clock transition in 87Sr”, Appl. Phys. Express vol. 5 022701, 2012.
306

K. Matsubara, et al., “Direct comparison of a Ca+ single-ion clock against a Sr lattice clock to verify the absolute
frequency measurement”, Optics Express, vol. 20, p. 22034-22041, 2012.

Global Navigation Satellite Systems
CLUB E
Tuesday, July 23 2013, 04:30 pm - 06:00 pm
Chair:

Patrizia Tavella
INRIM

IFCS-EFTF5-F2-1

Exploring the performance of GNSS frequency transfer
Petit G.1, Kanj A.1,2, Harmegnies A.1, Delporte J.2, Mercier F.2, Perosanz F.2
1

Time Department, BIPM, 92312 Sèvres, France
2
CNES, 31401 Toulouse, France
Email: gpetit@bipm.org

Since many years, the time and frequency community has been using GNSS phase and code
observations to compute time links. The BIPM has adopted the Precise Point Positioning (PPP)
technique because it is relatively simple to operate while delivering state of the art results, thanks to theprecise satellite orbits and clock products generated by the International GNSS Service.
In this paper, we investigate the time stability of PPP links for an averaging duration between a few
hours up to tens of days, which directly provides the performance of such links for frequency transfer.
Besides instabilities intrinsic to the receiving systems, the main limitations at these averaging times
come from uncertainties in the phase ambiguity resolution and from the marginal effect of thesimultaneous resolution of other parameters such as troposphere delay and station position.
We study several approaches aiming at improving the PPP results over long durations by ensuring acontinuous processing over the whole interval under study rather than concatenating results obtained
over short intervals. One approach is the use the Integer-PPP (IPPP) technique implemented by the
CNES. IPPP is based on the resolution of the phase data integer ambiguities at the un-differenced leveland needs precise GPS satellite orbit and clock products with a priori knowledge of individual satellite
fractional-cycle biases as derived by the CNES-CLS IGS Analysis Center.
We compare the different GNSS phase and code solutions with one another and with independent Twoway time transfer results. In order to best assess their achieved performances, we then use the different
methods to compute links between laboratories operating atomic fountains and study how the different
results succeed in attaining the known frequency stability of the fountains. This test may be limited atshort averaging time due to the sampling of the fountain data but is most efficient for averaging time
above one day.

IFCS-EFTF5-F2-2

Dual-Frequency Time Transfer Unit for Comparisons of the Remote
Clocks Using GLONASS and GPS Signals
P.P.Bogdanov, A.S.Bandura, M.G.German, K.S.Kol’chenko, O.E.Nechaeva“Russian Institute of Radionavigation and Time” JSC, St.Petersburg, Russia
E-mail: niiss@rirt.ru
The method of using GLONASS and GPS signals is still being used for accurate comparison of theremote clocks.
Time Transfer Unit (TTU) using GLONASS and GPS signals developed at Russian Institute ofRadionavigation and Time (RIRT) in 2002 was the first Russian device to realize this method. However,its abilities were considerably limited as it was designed on the base of 16-channel single-frequency
GLONASS/GPS receiver.
In this connection, the new Time Transfer Unit (TTU-1) based on 36-channel dual-frequency
GLONASS/GPS receiver was developed in 2011. TTU-1 is intended for determining the offset between
local clock and GLONASS-time and GPS-time with the purpose of subsequent determining the mutual
time and frequency offset between remote clocks, as well as for generating time scale signals
synchronized to Russian National Universal Time Coordinated UTC(SU) or to GLONASS-time.
TTU-1 provides the following output data:- time measurement results in the standard international format “cggtts_format_v2” including:
L1C - L1 code measurements;
L2C - L2 measurements;
L3С - ionosphere-free combination of dual-frequency code measurements;
CL3 - ionosphere-free combination of dual-frequency code and carrier phase measurements;- measurements of the radionavigation parameters and digital information included into navigation
message from SV in the standard international format RINEX.
Antenna box and receiver are calibrated during their manufacturing process. The calculated signal
delays for GLONASS and GPS are accounted for then during the measurements processing. The special
testing equipment including GPS/GLONASS signals simulator are used to calibrate the devices. The
total error of the determined absolute signal delays is about 5 ns. Besides, the delay corrections aremeasured for each GLONASS frequency with the error no more than 1 ns.
Test results show that the accuracy parameters of the new TTU-1 are higher than the samecharacteristics of TTU equipment and TTS-3 и TTS-4 receivers, mostly when operating by GLONASS
signals.
The improvement of time comparison accuracy is possible in post-processing mode with using a
posteriori ephemeris and other data from GNSS information centers including Information/AnalyticalCenter of “TSNIIMASH” Federal State Unitary Enterprise.

IFCS-EFTF5-F2-3

Advances in multi-GNSS time transfer
Defraigne P.°, Harmegnies A.*, Petit G. *°Royal Observatory of Belgium, Brussels, Belgium*BIPM, France
Email: p.defraigne@oma.be
Measurements from Global Navigation Satellite Systems (GNSS) are used since the eighties to perform
precise and accurate Time and Frequency Transfer (TFT). Only the GPS constellation was used during
the last 25 years, with some experiments based on GLONASS measurements. The GLONASS
constellation is presently completed, the first four Galileo satellites are already operational, and the
COMPASS system also provides signals that can be additionally used for time transfer. Increasing thenumber of satellites, and hence the number of observations, will reduce the noise level of the solution.
However, such a combination requires the knowledge of some inter-system biases in the receivers andthe existence of satellite clock products which can be expressed with respect to a common reference.
This paper will propose recent advances in these combinations, focusing on GPS, GLONASS and
Galileo.

IFCS-EFTF5-F2-4

Stability of GPS PPP link on the baseline of 270 km compared to
glass fiber measurements
J. Nawrocki*, P. Dunst*, D. Lemański*, P. Nogaś*, P. Lejba*, A. Czubla**, R. Osmyk**,P. Szterk***
Polish Academy of Sciences, Space Research Centre, Borowiec Astrogeodynamical
Observatory, Borowiec, Poland**
Time and Frequency Laboratory, Electricity Department, Central Office of Measures,
Warsaw, Poland
Email: nawrocki@cbk.poznan.plCentral Office of Measure (GUM) in Warsaw and Borowiec Astrogeodynamical Obserwatory (AOS) in
Borowiec near Poznan are equipped with TTS-4 time transfer systems, GPS/GLONASS dual frequency
receivers, lately calibrated for GPS C/A code during BIPM calibration campaign in 2010. Bothlaboratories, GUM and AOS, distant from each other by 270 km geographically, are, since February
2012, also connected by the optical fiber time transfer link307 with stabilization of propagation delay atthe level of about a few-dozen of picoseconds. This optical fiber link is fully calibrated for time transfer
with total expanded uncertainty of about 0.6 ns, and its calibration can be easy updated in the case of thechange in the optical path, or in configuration of transmitted signals. Glass fiber measurements,
currently performed every 5 s, are not limited by satellites observation schedule, and are not disturbed
by the changing conditions in the ionosphere as in satellite methods.
After the first stage of verification of operation of the optical fiber link between GUM and AOS, wehave started to monitor stability and precision of GPS PPP time transfer link between our laboratories,
using as a reference the results obtained from glass fiber measurements. This allows us not only tocompare the stability of measurement results obtained with the usage of the both methods, but also to
reduce the common bias and noise of the compared clocks by differential analysis. It is a very good
method for improvement of the GPS PPP time transfer calculations and further development of the glass
fibre method.
In this presentation, we plan to show and discuss the latest results of our measurements and analysis
performed over the last year for UTC(PL)-UTC(AOS) glass fibre link and GPS PPP method.

307Ł Śliwczyński, P. Krehlik, A. Czubla, Ł. Buczek and M. Lipiński, “Dissemination of time and RF frequency via astabilized fibre optic link over a distance of 420 km”, Metrologia vol. 50, pp. 133-145, 2013.

IFCS-EFTF5-F2-5

Time and Frequency Transfer Using Satellite Based Augmentation
System GAGAN
Petr Panek, Alexander Kuna
Institute of Photonics and Electronics, AS CR, Chaberska 57, 182 51 Prague, Czech Republic
Email: panek@ufe.cz
GAGAN (GPS - Aided Geo Augmented Navigation) is an Indian satellite navigation system whichaugments GPS and makes it suitable for safety critical applications. It is one of the Satellite Based
Augmentation Systems (SBAS). GAGAN uses a geostationary satellite transmitting signals almost
identical to the GPS signals thus it can be used for time and frequency transfer in similar way. In
contrast to the European EGNOS, this system already supports the navigation function and it transmits
signals both in L1 and L5 frequency channels. The signals are available in good quality in the central
Europe area.
We used the GAGAN signals for an experimental common-view time transfer between IPE Prague and
PTB Braunschweig which is a distance of 370 km. The stability of the measured time difference waslimited by stability of the clock in IPE and could be considered TDEV(1 min) < 30 ps and
TDEV < 250 ps for averaging intervals up to 1 hour. GTR51 time and frequency transfer GNSS
receivers were employed at both sites.
We analyzed one-minute measurement data from a continuous one-day measurement. The L1 code
measurement has markedly lower accuracy compared to a GPS common-view. This is caused by therather narrow bandwidth of the SBAS signals in this frequency channel. The observed fluctuations canbe described as white noise with standard deviation of 7 ns. The L5 code measurement provides muchbetter precision. In this case we assessed the stability TDEV < 1.3 ns for averaging intervals from 1 min
to several hours. Since the geostationary satellite moves just slightly towards the receivers, the observed
variations caused by the multipath effect are very slow compared to GPS.
The results obtained from the carrier phase measurements are promising. The stability of the ionosphere
free combination is TDEV(1 min) < 40 ps and for longer averaging intervals it follows the expectedstability of the measured time difference. Interesting results followed from our comparison of the single
frequency measurements and the ionosphere free combination where relatively fast fluctuations inducedby ionosphere are obvious in the single frequency measurements. During the daytime, the amplitude ofthese fluctuations reaches 5 ns in the L1 frequency channel. This behavior is quite far from classicalionospheric delay models.
We believe that using GAGAN and other SBAS for permanent carrier phase frequency transfer could be
ideal solution for continuous comparisons of precise frequency sources.

IFCS-EFTF5-F2-6

Preliminary Implementation ofTime and Frequency Transfer by BDS
LIANG Kun1, JIN Zhaofeng2
1

Division of Time and Frequency Metrology, National Institute of Metrology, Beijing, China
2
Beijing Hoyateq Science&Technology Co., Ltd, Beijing, China

Email: liangk@nim.ac.cn
Abstract: Since 27th Dec 2012, BeiDou Navigation Satellite System(BDS) Signal in Space Interface
Control Document-Open Service Signal B1I (Version 1.0)1 has been released. It mainly includes thesystem introduction, signal standards and navigation message, which defines the related contents ofopen service signal B1I between BDS and users terminals. Error correction and clock bias solution for
BDS have been studied, and time and frequency transfer method by BDS has been developed by
NIM(National Institute of Metrology, Beijing, China). Based on BDS OEM model, the original BDS
observation has been acquired and the BDS C1 and P2 code time and frequency transfer has been
implemented preliminarily after the difference between BDT(BDS system time) and GPST(GPS systemtime) is taken into account. To verify its performance and feasibility, the remote time and frequency
transfer experiments and the CCD(Common Clock Difference) experiments have been implemented,
using the two BDS receivers and the other GPS receivers including IMEU, IMEN and IMEW
sites(NIMTFGNSS-12 receivers), IMPR and BJNM sites(Septentrio PolaRx2eTR and PolaRx3eTR
receivers respectively) and IMEJ site(Dicom GTR50 receiver) of NIM located at NIM. The stability andaccuracy of BDS time and frequency transfer have been evaluated. The long baseline resultscharacterize that the remote transfer performance of BDS time and frequency transfer is comparablewith GPS(Global Positioning System). The standard deviation of the BDS C1 code CCD results using
AV(All-in View) method could be about 3 ns with one day measurement. In the near future, using BDS
post, near real-time or real-time precise ephemeris products, BDS carrier phase time and frequency
transfer will be studied and applied at NIM.
References:
2. China Satellite Navigation Office, “BeiDou Navigation Satellite System Signal In Space Interface
Control Document Open Service Signal B1I (Version 1.0),” 2012
3. LIANG Kun, ZHANG Aimin, GAO Xiaoxun,WANG Weibo, NING Dayu，ZHANG Side, “Studyand Development of a New GNSS Receiver for Time and Frequency Transfer,” Proc. of EFTF 2012,
pp. 529-536, 2012.

Wireless Sensors
CLUB D
Tuesday, July 23 2013, 04:30 pm - 06:00 pm
Chair:

Leonhard Reindl
University of Freiburg

IFCS-EFTF4-F3-1

An Integrated SAW Sensor with Direct Write AntennaMark W. Gallagher1, William Smith2, Donald C. Malocha1
1Deparment of Electrical Engineering and Computer Science,
University of Central Florida, Orlando, FL 32816
2
MesoScribe Technologies Inc., St. James, New York 11780
Email: MGallagher@knights.ucf.edu

This paper presents a wafer-level integrated SAW sensor using conventional thin-film fabrication for the
SAW, and the direct write of a thicker dissimilar metal for the antenna. Previous proof-of-concept
results using thin antenna films demonstrated the feasibility of planar device integration, but had limited
interrogation range.308 For the first time, a direct write process is utilized to deposit the antenna
conductor onto the SAW substrate, providing ease of fabrication, optimal film thickness, and superior
adhesion. Shown in Figure 64, the automated thermal spray process selectively deposits conductive or
dielectric films onto a CAD defined area for rapid, conformal fabrication, allowing sensor integration ona range of surfaces. Results presented will show an increase in range, compared to previous work,through an improved low loss design.
Using the direct write process, shown in Figure 64, 15 μm thick copper is ‘written’ onto lithium niobate
without a mask. Thick antenna traces lower antenna resistive losses, because of increases in conductivity
and decreased skin depth effects. The traces adhere well to the 80 nm aluminum SAW transducer pads
that are patterned previously by a traditional photolithographic process. The process allows multiple
metal levels, trenching, and trimming, for optimum design and fabrication of research or a commercial
product. The updated design yields three devices on a 76 mm wafer and requires no mechanical bonds;
bond free devices are ideal for demanding environmental sensors.
Antenna gain and bandwidth trade-offs must be made to the integrated design to meet device size andsystem performance requirements. The design of a 915 MHz meandered dipole antenna with low
mismatch loss and maximized radiation efficiency over an 8% SAW fractional bandwidth isdemonstrated. Experimental performance results of antennas fabricated on standard FR4 and on-wafer
by electroplating or direct write process will be contrasted. Temperature sensors are fabricated on YZLiNbO3 and simultaneous operation, over temperature, in a multi-sensor system will be demonstrated
wirelessly at several meters. The integration of SAW and direct write technology offers a multitude ofopportunities for new sensor and communication system embodiments.

(a)

(b)

Figure 91: (a) The automated direct write robot printing to a part. (b) An example of a 915 MHz SAW sensor and direct write
dipole antenna integrated onto a 76 mm Y-cut lithium niobate wafer.

308

M. W. Gallagher, B. C. Santos and D. C. Malocha, "Wireless wideband SAW sensor - antenna design," in IEEE Int.
Frequency Control Symp., Newport Beach, CA, 2010, pp.291-296.

IFCS-EFTF4-F3-2

Ultra-Wide-Band SAW sensors and tags
Lamothe Marc1, Plessky Victor2, Ostertag Thomas3, Friedt Jean-Michel1
1

Temps-fréquence, Femto-st institute, Besancon, France
2
GVR Trade SA, Gorgier, Switzerland
3
RSSI GmbH, Geretsried, Germany
Email: marc.lamothe@femto-st.fr

SAW tags and sensors often operate in 2.45 GHz ISM band with relatively narrow Band=82.5 MHz
available there. The characteristics of SAW tags and sensors can be radically improved due to thepossibility to use ultra wide band (UWB) frequency range [1]. Wide band means large bit capacity B*T
with even decreased size of the device. In this work we develop prototype devices operating in
2000MHz- 2500MHz UWB frequency range. First measurement results with new UWB reader will bereported.
A few different SAW sensor devices for operation in the UWB were designed, manufactured andtested. The test devices included chirp LFM IDT, wide band reflectors. For simulation of devices
FEM/BEM software “FEMSAW” ( homemade software ) was used. The UWB reader operating incontinuous wave radar regime was developed and manufactured. The current reading distance is about 1
meter but this distance should be increased.
The first remote measurements has shown that we get compressed RF pulses of about 2 ns duration(Fig.1), including unique RF pulse of a few sinusoids with amplitude modulation. Due to this many
advantages can be obtained: the precise measurement of the pulse position is possible by correlation methods, avoiding thephase ambiguity problem. The precision of the temperature definition of 1 °C can be obtained.
Only 2 reflectors are necessary for such a sensor.
 The correlation method works even in multi-path environment with strong reflections form metal
objects
 The short compressed pulses allow measuring a number of sensors simultaneously justseparating them in time (TDMA). Figure 1 shows 2 sensors measured simultaneously, eachdevice including 3 reflectors.
 For the tag application in theory at least 100 tags can be identified simultaneously in a limited
temperature range ΔT< 100°C. For such
limited number of tags there is no“collision” problem.
The measurements are currently under way. The
radiated power level will be estimated and thereading distance for the signals satisfying the US
UWB standatds will be determined.

Fig. 92: wireless measurement of two
sensors.

IFCS-EFTF4-F3-3

A Wireless Langasite Resonant Electrical Field/Voltage Sensor
Haifeng Zhanga and Tinghui Fanb
Department of Engineering Technology, University of North Texas, Denton, TX, 76207b
Department of Electrical Engineering, University of North Texas, Denton, TX, 76207
Email: haifeng.zhang@unt.edu
aFrequency(MHz)Abstract
Langasite (La₃Ga₅SiO₁₄), a promising new piezoelectric crystal, has attracted interest frompiezoelectric communities around the world for its superior behavior such as having a high Q, stablefrequency-temperature behavior, high electrical-mechanical coupling coefficient and no phase transition
to a high temperature form. Langasite resonators are generally more sensitive to electrical fields thanquartz resonators as they have higher
piezoelectric coefficient [1], which isideal for high accuracy electrical field
Wireless
6.306
sensorapplications
in
harsh
Wired
environments. This article presents a
6.3059system for a wireless langasite
resonator electrical field sensor. The
6.3058system uses frequency conversion
6.3057techniques to convert the sensor’s
ultrasonic signal to a microwave signal6.3056in order to transmit the signal6.3055
wirelessly without digitization. The
sensor is able to transmit the ultrasound
6.3054signal by using passive componentsthat modulate and transmit the full
200
300
400
500
600
700
waveform. A special circuit is designed
Voltage(Volt)
to apply the high voltage on the Fig. 1. The measured frequency-voltage relation
langasite resonator without causing for the doubly rotated langasite resonator (YXlw
damage to other instruments. The θ/Ф 45°/85°).
wireless transmission system wastested using a doubly rotated plano-plano langasite resonator (YXlw)θ/Ф 45°/85° operating on its third
overtone (6.304844 MHz) as its sensor. Wireless system data obtained using a network analyzer wascompared with similar wired system data. The electric field-frequency effect was measured for both
wired and wireless configurations. The result shows a good agreement between the wired and wirelesssignals (Fig.1). The demonstrated system has a potential for high voltage/electrical field sensing
applications in harsh environments.

[1] H. Zhang, J. A. Turner, J. S. Yang, and J. A. Kosinski, “Electroelastic effect of thickness mode
langasite resonators,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control., vol. 54, no. 10, pp. 2120-2128,
2007.

IFCS-EFTF4-F3-4

Resonant SAW Torque Sensor for Wind Turbines
Victor Kalinin1, Arthur Leigh1, Alexander Stopps1, Estefania Artigao2
1

2

Transense Technologies plc, Bicester, Oxon., UK
Brunel Innovation Centre, Brunel University, Cambridge, UK
Email: victor.kalinin@transense.co.uk

Wind farms are at the moment one of the fastest growing sources of renewable energy. However, thecost of electricity generated by offshore wind turbines is still noticeably higher than that for fossil fuelpower plants, and maintenance cost is an important contribution to it. Up to 80% of this cost is
associated with unexpected failures of rotating components that could be prevented by predictive andcorrective maintenance based on adequate condition monitoring systems. Currently they mainly include
vibration, temperature and oil debris sensors but there is also a clear demand for sensing torque. Thatwould allow a more accurate estimation of load on rotating parts, correlation of this load with the dataobtained from other sensors and overload protection.
At the moment torque sensors used on wind turbines are mostly realized with strain gauges but the latterare difficult to apply, require telemetry system for signal transmission and non-contact power supply,
they are expensive and used mainly at the development stage rather than for continuous load monitoring.
The aim of this paper is to present a batteryless non-contact SAW torque sensor suitable for easy aftermarket installation on the high-speed shafts of windturbine gearboxes.
Resonant SAW torque sensors have been developed
for automotive industry309 but in this case the SAW
die is attached by an adhesive directly to the surface
of a relatively small part that can be cured in an oven.
Dimensions of the wind turbine gearbox high-speed
shafts are too large for curing them in ovens. A novel
design of a torque plate transducer with the SAW
sensing element is proposed that allows easy clampingof it on the surface of a large shaft. The main design
issue is repeatability of the sensor readings andminimization of the hysteresis associated with a stateof the interface between the shaft and the transducer. Fig. 93: Torque plate transducer with the SAW
Another issue is a design of the RF rotary coupler resonant sensing element installed on test shaft andwith a large 20 mm gap between the rotor and the connected to a large diameter RF coupler.
stator that would tolerate vibrations of the shaft andprovide wireless resonant frequency measurements insensitive to the angular position of the shaft and its
radial and axial movement. The use of a specially designed test shaft for calibration of the sensor within
the temperature range from +20°C to +85°C is discussed in the paper. The achieved accuracy of thesensor tested after calibration is approximately 1% of the full range that is ±5 kNm. Installation of thesensor on the 750 kW NEG MICON 48 wind turbine is also discussed.

309

V. Kalinin. “Wireless physical SAW sensors for automotive applications”, Proc. IEEE Int. Ultrason. Symp., pp. 212 –
221, 2011.

IFCS-EFTF4-F3-5

High-overtone Bulk Acoustic Resonator as passive sensor acting a buriedcooperative target interrogated by Ground Penetrating RADAR.
J.-M Friedt1, A. Saintenoy2, T. Baron3, E. Lebrasseur3, T. Laroche3, S. Ballandras3, M. Griselin4
1

SENSeOR, Besançon, France
IDES, UMR CNRS 8148, Université Paris Sud, France
3
FEMTO-ST Time & Frequency department, UMR CNRS 6174, Besançon, France
4
ThéMA, UMR CNRS 6049, Université de Franche Comté, Besançon, France
2

Email: jmfriedt@femto-st.fr
Acoustic transducers have demonstrated superior capabilities when used as passive sensors interrogatedthrough a wireless radiofrequency (RF) link. However, exploiting these devices has been associated withdedicated hardware.
In this presentation, we consider acoustic sensors as passive cooperative targets to Ground Penetrating
RADAR (GPR), one particular type of impulse mode ultrawideband characterization instrument widelyused for geophysical purposes. Because acoustic resonators and delay lines only operate in a single
frequency band defined by the spatial periodicity of the interdigitated transducer, one particulartransducer can be probed by only one associated GPR operating in the same frequency bands.
Various RADAR frequencies are used for various applications as a trade off between penetration depthof the electromagnetic wave and spatial resolution: the higher the operating frequency as defined byantenna dimensions, the shallower the penetration depth but the better the spatial resolution. Our
objective here is to demonstrate the use of High-overtone Bulk Acoustic Resonators (HBAR) as GPR
cooperative targets compatible with multiple frequency bands.
HBAR is a bulk acoustic wave transducer in which a stack of piezoelectric substrate acting as the active
layer (conversion from electromagnetic to mechanical wave) and a thick substrate (low acoustic loss
medium) are combined to generate a comb of modes in the frequency domain. Since the Fouriertransform of a frequency comb is a comb of reflections in the time domain, the impulse response of sucha transducer is a series of echoes whose delay is representative of the acoustic velocity. If substrateorientations are selected to exhibit strong dependency with a given physical property, measuring thedelay between echoes allows for the measurement of this quantity.
A same HBAR transducer has been interrogated using a commercial, off the shelf Malå RAMAC CUIIGPR unit operating at 100 and 200 MHz ranges (the hardware remains the same and the operating
frequency is selected by changing the length of the dipole antenna fitted to the emitter and receiverunits). The temperature of the transducer is extracted from a cross-correlation between adjacent echo
signals, yielding a measurement insensitive to environmental conditions other than the quantity underinvestigation (e.g distance between RADAR and sensor). We thus demonstrate the compatibility of
acoustic transducers – either for identification or measurement purposes – as buried sensors with
virtually infinite life expectancy once installed in environments unsuitable for battery replacement (civilengineering structures, concrete curing and stress, soil temperature measurement or stress measurementin the case of moving environments such as glacier or landslides).

IFCS-EFTF4-F3-6

Passive Wireless Surface Acoustic Wave CO 2 Sensor for
Geological Sequestration Sites Monitoring
Yizhong Wang, Minking K. Chyu, Qing-Ming Wang*,
Department of Mechanical Engineering and Materials Sciences, University of Pittsburgh,
Pittsburgh, PA, USA
Email: qiw4@pitt.edu
Geological sequestration, where the CO2 was collected and dumped into the mines and oil fields deep
under ground, has attracted lots of attention. There is urgent need for developing a sophisticated systemthat can monitor the ground leakage in those remote sequestration sites. Surface acoustic wave sensor
equipped with on-chip sensitive layer is the best choice310 for low cost wireless monitoring ofsequestration sites leakage monitoring with minimum power consumption.
Surface acoustic wave sensor with delay line structure was adopted. The sensitive layer was initiallycomposed of carbon nanotube (CNT) and polyimide (PI). CNT was chosen due to its high surface
volume aspect ratio and chemical stability. PI wasused to promote sensor performance in harshenvironment.
Test of PI based nanocomposite showed less than
0.4% resistance increase over pure CO2. Based on
sensor frequency dependence on film conductivity,
this will cause about 10ppm frequency change.
Polyethyleneimine (PEI) was then used for its betterchemical reaction between CO2 gas molecule and
CNT. The gas response for the new nanocomposite
was about 10% resistance increase under pure CO2, Fig. 94: Sensor response to CO2 with various
which gave an estimated 1000ppm frequency concentrations.
change. The fabricated sensor frequency change
was around 300ppm for pure CO2. The lowest
detection limit of the sensor is 1% gas
concentration, with 36ppm frequency change.
With paralyne packaging, the sensor frequencychange on humidity reduced to less than 100ppm
from over 1000ppm for unprotected sensor while
maintaining the same gas sensing performance.
Wireless module was tested and showed over one
foot transmission distance at preferred parallel Fig. 95: Sensor response to different relative
humidity levels for sensors with and withoutorientation.
parylene packaging.

310

Wen Wang, et al, Wireless surface acoustic wave chemical sensor for simultaneous measurement of CO2 and humidity. J.
Micro/Nanolith. MEMS MOEMS. Vol.8(3),pp.031306.1-6. Jul–Sep 2009.

IFCS-EFTF Awards and Plenary Talk
CH
Wednesday, July 24 2013, 08:30 am - 10:00 am
Chair:Plenary III-1

Gaetano Mileti
Université de Neuchâtel

Chip-scale atomic clocks
CLUB E
Wednesday, July 24 2013, 10:30 am - 12:00 pm
Chair:

Miao Zhu
Agilent Technologies

IFCS-EFTF3-G1-1

Spatially Resolved Measurement of Relaxation Times
in a Microfabricated Vapor Cell
Andrew Horsley1, Guan-Xiang Du1, Matthieu Pellaton2, Christoph Affolderbach2,
Gaetano Mileti2, and Philipp Treutlein1
1

2

Departement Physik, Universität Basel, Switzerland
Laboratoire Temps-Fréquence, Institut de Physique, Université de Neuchâtel, Switzerland
Email: andrew.horsley@unibas.ch

Microfabricated vapor cells are an important tool for atomic physics applications, showing particularsuccess in miniaturised atomic clocks311 and DC electromagnetic field sensing312. As a new application,
imaging of microwave magnetic fields using a vapor cell has recently been demonstrated by ourgroup313. A thorough knowledge of the properties of a cell is prerequisite to precision measurements.
For microfabricated cells and imaging applications,
T1 (µs)the spatial dependence of relaxation times andexcitation fields are of particular importance. We
present the spatially resolved characterisation,
performed using time-domain Ramsey and Rabi
measurements, of a 5 mm diameter, 2 mm thickmicrofabricated cell, filled with natRb and 80 mbar of
N2 buffer gas314.
Atomic relaxation is described by the T1 and T2 times,
representing the population and coherence lifetimes,
respectively. The dominant relaxation mechanisms ina vapor cell are Rb-wall, Rb-buffer gas and Rb-Rb
collisions. The coherence lifetime is also limited byinhomogeneities in applied static and microwave
magnetic fields. Both lifetimes can be obtained in asingle time-domain Ramsey measurement.
Fig. 96: T1 times across the cell, obtained using
We characterise T1 and T2 relaxation in the cell as a relaxation in the dark, at a cell temperature of 90°C.
functionofposition,
performing
Ramsey Lifetimes are longer in the centre of the cell, where
the effects of destructive Rb-wall collisions aremeasurements as we scan a narrow laser beam across minimised.
the cell. We also probe the homogeneity of ourapplied static and microwave fields using Rabi sequences. In addition we have implemented an imaging
technique, whereby a CCD chip is used to perform measurements over the entire cell simultaneously. As
an example, figure 1 shows an image of T1 times across our cell.
This work was supported by SNSF and ESA. We thank Y. Pétremand for filling the cell.
311

Svenja Knappe et al “A microfabricated atomic clock” Appl. Phys. Lett. 85, 1460 (2004)

312

D. Budker and M. Romalis, “Optical magnetometry” Nat. Phys. 3, 227 (2007)

313

Pascal Böhi and Philipp Treutlein “Simple microwave field imaging technique using hot atomic vapor cells” Appl. Phys.
Lett. 101, 181107 (2012)314

M Pellaton, C Affolderbach, Y Pétremand, N de Rooij and G Mileti, “Study of laser-pumped double-resonance clock
signals using a microfabricated cell” Phys. Scr. T149 (2012)

IFCS-EFTF3-G1-2

The Integrated Swiss Miniature Atomic Clock
Jacques Haesler, Laurent Balet, Thomas Overstolz, Jörg Pierer, Rony Jose James,
David Ruffieux, Steve Lecomte
CSEM SA, Jaquet-Droz 1, CH-2002 Neuchâtel, Switzerland
Email: jacques.haesler@csem.ch
The detailed design of the Swiss Miniature Atomic Clock (Swiss-MAC) was presented by CSEM at the2012 EFTF315. This paper describes the progress made since then towards the realization of theintegrated Swiss-MAC, by presenting a first prototype showing preliminary but very promising
performances.
Miniature atomic clocks (MACs), typically based on the coherent population trapping scheme (CPT),
show the promise of having miniature (< 1 cm3) and low-power (< 100 mW) portable microwave
frequency standards. The Swiss-MAC was designed
to target such state of the art specifications. The
current prototype integrates most of the desired
functionalities, except the vacuum encapsulation of
the physics package and its integrated temperature
regulation. The prototype is powered by a separate
PCB equipped with a battery pack and different
monitoring and debugging inputs/outputs. The main
PCB has dimensions of 50 x 100 mm2 with 1/3rd ofits surface populated by test jumpers and connectors.
The core physics package is realized by a stacking of
PCB layers (Fig. 1). It has dimensions down to 11 x Fig. 97: Picture of the physics package developed
for the Swiss Miniature Atomic Clock11 x 8.5 mm3 (1 cm3), including the functionalizedatomic vapor cell with dimensions downsized to 4 x
4 x 1.6 mm3 (26 mm3). The core physics package is mounted in a commercial ceramic package forvacuum encapsulation. The resulting assembly is surrounded by an external Ø 42 mm magnetic
shielding, the overall volume of the physics package reaching 22 cm3. The Swiss-MAC prototype iscontrolled by means of a LabVIEW® interface communicating with an MSP430 microcontroller. The
latter drives the 3rd generation of a dedicated proprietary ASIC, with built-in RF lock loop and laser
lock loop, and with integrated laser bias current source, three temperature sensors, and four heating
current sources.
The Swiss-MAC prototype is currently in its integration and test phase. The main lock loops could
already be closed and preliminary frequency stability measurements were successfully be realized using
an external miniature glass atomic vapor cell (100 mm3). The results, reaching σy = 3∙10-11 at one day
integration time and an impressive σy = 6∙10-11 at 1 s are very close to telecom specifications. Moreover,they confirm that our integrated electronics supports good short term frequency stability. Improvements
and further tests are ongoing. The complete prototype will be fully characterized in 2013 and more
results are expected for the conference.

315

J. Haesler et al., “Swiss Miniature Atomic Clock: first prototype and preliminary results”, European Time and Frequency
Forum (EFTF), Gothenburg, April 2012.

IFCS-EFTF3-G1-3

Double resonance spectroscopic studies using
a new generation of microfabricated microwave cavity
M. Pellaton1, M. Violetti2, C. Affolderbach1, J.-F. Zürcher2, A. Skrivervik2, G. Mileti1
1
2

Laboratoire Temps Fréquence (LTF), Université de Neuchâtel, Neuchâtel, Switzerland
Laboratory of Electromagnetics and Acoustics (LEMA), EPFL, Lausanne, Switzerland
Email: matthieu.pellaton@unine.ch

Our research concerns a miniature vapor-cell atomic clock
based on double-resonance instead of CPT316, using a newly
designed microwave resonator, the -LGR317, and its
dedicated micro-fabricated cell318 (see Fig. 1). In thiscommunication we present an improved version of the atomic
resonator package using an 87Rb cell and more detailed
spectroscopic studies, including analysis of the main sourcesof medium and long term frequency instability.

Fig. 98: Atomic resonator used for thisPreliminary measurements show promising results. The study; internal cell dimensions are
Zeeman spectrum (see Fig. 2) demonstrates a clean and well 4 mm diameter and 4.05 mm height.
controlled microwave field sustained by the resonator that iscomposed of a stack of planar electrodes. The determination of
its field orientation factor319 (FOF) gives an excellent value of
0.7.
After a first optimization step, a nearly 13% contrast signal
with a FWHM of 3.8 kHz is obtained; this allows a shot-noise
limit prediction of 2.8 x 10-12 τ-1/2. Fig. 3 shows the stability
obtained using this signal, which is in good agreement with theFig. 2: Zeeman’s spectrum at low RF
predicted signal-to-noise limit of 7 x 10-12 τ-1/2. Long term power showing excellent fieldstabilities issues such as light shift and temperature shift will geometry.
also be discussed.
Acknowledgement: This work was supported by the Swiss
National Science Foundation and the European Space Agency(ESA). We thank Y. Pétremand (EPFL, SAMLAB) for the cellfabrication, and F. Gruet, P. Scherler, and M. Dürrenberger(all from LTF) for their contributions to the realization of the
hardware.
Fig. 3: Overlapping Allan deviation.
316

T. Bandi et al., “Double Resonance in Alkali Vapor Cells for High Performance and Miniature Atomic Clocks”, Invited
talk of G. Mileti and Proc. IEEE IFCS 2012, pp. 1-6 (2012)317
M. Violetti et al., “New Miniaturized Microwave Cavity for Rubidium Atomic Clocks”, Proc. IEEE Sensors 2012, pp. 315318 (2012).
318
Y. Pétremand et al., “Microfabricated rubidium vapour-cell with a thick glass core for small scale atomic clock
applications”, J. Micromech. Microeng. 22, 025013 (2012).
319
C. Stefanucci et al., “Compact Microwave Cavity for High Performance Rubidium Frequency Standards”, Rev. Sci.
Instrum.83, 104706 (2012).

IFCS-EFTF3-G1-4

Short term noise investigation on a compact CPT clock
Danet Jean-Marie, Yun Peter, Guerandel Stephane, de Clercq Emeric
LNE SYRTE, Observatoire de Paris, Paris, France
Email: jean-marie.danet@obspm.fr
Towards the development of on-board atomic clock, alkali vapor cells clocks have shown that besides
their robustness and relative simplicity, cell technology clocks are competitive with the cold atoms
compact setups in term of stability320 321. Among the different vapor cell clock technologies, thecoherent population trapping (CPT) prototype developed at SYRTE offer an alternative where no
microwave cavity is needed. The microwave is optically carried by the frequency difference between
two lasers. Using crossed linear polarized beams and Ramsey temporal interrogation, signals with 15 %contrast and 125 Hz linewidth have been observed. Such a signal, combined with a noise at the shotnoise limit would lead to sub 10-13 τ-1/2 stability clocks. In this paper we report investigations on thenoise processes currently limiting the short term
stability of the clock at the level of 5.5 10-13 at 1s.
Five main noise sources are investigated: magnetic
field, beam polarization, laser frequency, laser
intensity and finally microwave phase. A contribution
to the clock stability below 10-14 at 1s is shown for thetwo first ones. The effect of the optical frequency
detuning has been measured and its conversion on theclock stability is under investigation. The influence ofthe laser intensity noise has been carefully studied, it
is not negligible in the 10-13 range. A stabilization
system has been implemented lowering the RIN of 15
dB down to -137 dB/Hz-1/2 at 160 Hz. Finally the local
oscillator noise contribution to the clock stability has
been studied using the Dick formalism322. This Fig. 99: Sensitivity function of a pulsed CPT clock.
aliasing effect, well understood for a two level system, Pumping 2ms, Free evolution time 4ms, Detection:
had never been investigated for a three level one as 25 µs, 200 µs after switching lasers on.
the CPT. The numerical calculation, in good
agreement with measurements, allowed us to deduce a phenomenological equation for the Dick effect in
CPT, usable for others CPT clocks. The application of those calculations to our prototype pointed out
the local oscillator as main noise source contributor, followed by the intensity noise. Solutions havebeen designed and will be implemented on our set-up. The latest results will be shown at the conference.

320

S. Micalizio et al., Metrologia, vol 49, 425, 2012.

2

F. X. Esnault et al., Phys. Rev. A, 82, 033436, 2010.

3

G. J. Dick et al, in Proc. 19th Annu. Precise Time Time Interval conf., pp. 133–147, 1987.

IFCS-EFTF3-G1-5

Continuous and Ramsey spectroscopy of CPT resonances in Cs vapor
cells with push-pull optical pumping
X. Liu1, J-M. Merolla1, S. Guérandel2, C. Gorecki1, E. de Clercq2, R. Boudot1
FEMTO-ST, CNRS, 32 avenue de l’observatoire 25044 Besançon cedex, France.
LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, 77 avenue Denfert-Rochereau 75014 Paris, France.
1

2

Email: rodolphe.boudot@femto-st.fr
We studied theoretically and developed an experimental set-up to detect high-contrast CPT resonances in buffer-gasfilled Cs vapor cells using push-pull optical pumping (PPOP) [1]. The laser source of the system is a distributedfeedback (DFB) diode laser tuned on the Cs D1 line at 894.6 nm. A Mach-Zehnder electro-optic modulator (MZ EOM)is driven by a 4.596 GHz local oscillator to generate two first-order optical sidebands frequency-separated by 9.192
GHz. The dc electrode bias voltage of the MZ EOM is actively controlled using an original microwave synchronous
detector technique to stabilize optical carrier rejection (~28dB) at the output of the EOM. A Michelson-likeinterferometer allows to generate the so-called push-pull interaction scheme [1]. The laser light is transmitted through abuffer-gas-filled Cs vapor cell. The laser power at the output of the cell is detected by a photodiode.
Using a continuous (CW) interaction regime, the effect of the laser intensity onto the clock resonance parameters(linewidth, contrast, ratio linewidth-contrast) was studied for 3 different cells, including a microfabricated Cs-Ne cell.
The PPOP technique was found to be less efficient in microfabricated cells to obtain high-contrast resonances. For the
0-0 clock transition, CPT resonance contrasts as high as 78% were measured in a 5-cm-long cell with high operating
laser intensities [2], i.e at the expense of a relevant CPT line power broadening.
To circumvent this issue, with minor changes of the setup, we demonstrated the detection of high-contrast and narrow
CPT Ramsey fringes by combining PPOP and a temporal Ramsey-like interrogation. The major originality of theexperiment is the use of the single MZ EOM both for optical sidebands generation and light intensity modulation forpulsed interaction. As in [3], atoms interact with an optical pulse train sequence where each pulse is used both CPT
state pumping and atomic signal detection. Figure 1 shows typically obtained 166 Hz-linewidth Ramsey fringes with acontrast of 33% in a cm-scale cell. The impact of different experimental parameters (laser power, Ramsey time, CPT
pumping time,..) on the CPT fringe will be reported. First frequency stability results of the system, operating as an
atomic clock, in the CW regime and-or pulsed regime, will be reported at the conference.
1.35
1.30

CPT signal (a. u)

1.25
1.20
1.15
1.10
1.05
1.00
0.95
-15000-10000

-5000

0

5000

10000

15000

Raman detuning (Hz)Figure 1: Ramsey fringes detected with PPOP.
1

Y. Y. Jau et al., Phys. Rev. Lett. 93, 160802 (2004).

2

X. Liu et al., Phys. Rev. A 87, 013416 (2013)

3 T. Zanon et al., Phys. Rev. Lett. 94, 193002 (2005).

IFCS-EFTF3-G1-6

A Digitized Atomic Clock Based on Transient Oscillation of Detuned Coherent Population Trapping
Zhong Wang*, Jianye Zhao, Dong Hou, Shuangyou Zhang, Mingyu Wan, Yeqing Li and Daiting Shi
School of Electronics Engineering & Computer Science, Peking University,
Beijing, 100871, P. R. China*Email: zw@pku.edu.cn
We have implemented and experimentally verified a digitized atomic clock based on transientoscillation of detuned coherent population trapping (DCPT). In this design, the output standard
frequency can be achieved by directly adding/subtracting the transient oscillation frequency of DCPT
to/from the RF frequency, which is used for the pump laser modulation. We modulate the RF frequency
with a 100 Hz square wave, and the RF frequency is set to alternate between the ground state hyperfine
splitting frequency and the detuned frequency (a few kHz higher/lower). After the laser beam passes
through the rubidium atom cell, a series of laser intensity oscillation will be detected when the RF
frequency is detuned. This is the DCPT transient oscillation signal, and the frequency is theoreticallyequal to the detuning frequency.
In our DCPT atomic clock, the oscillation signal is detected, reshaped, and amplified, in order tofacilitate the digital processing. Since the detuning frequency is 103 Hz, using typical digital processing
with instability better than 10-6, we can extract the oscillation frequency with 10-3 Hz accuracy， whichallows us to acquire the detuning frequency of the RF oscillator accurate up to 0.1 Hz. When we use theRF oscillator signal as the reference frequency, and use the detected oscillation frequency to compensate
for the RF frequency detuning as well as its shift with time, we will be able to obtain the DCPT atomic
clock’s standard frequency, which equals the two ground states hyperfine splitting frequency. In our
preliminary experiments, the frequency instability of 1X10-11/1/2 (=1000s) has been achieved.
Comparing with traditional atomic clocks, This DCPT atomic clock does not require a circuit to lock the
microwave frequency. This eliminates the instability and loose locking probability brought on by thephase locking loop, which makes the DCPT atomic clock more stable and more reliable, especiallywhen used in harsh environments. In addition, the transient signal as the amplitude 3 to 4 times that of
the CPT signal, which further benefits observation and analysis. This data processing section can beeasily digitized and integrated. As a result, this scheme has great potential in the design and manufactureof miniature atomic clocks.

Space Missions and Clocks I
CLUB H
Wednesday, July 24 2013, 10:30 am - 12:00 pm
Chair:

Pierre Waller
ESAIFCS-EFTF5-G2-1

T2L2 : Five Years in Space
P. Exertier1, E. Samain1, Ph. Guillemot2, S. Léon2
N. Martin1, C. Foussard1, C. Courde1, J.M. Torre1, M. Laas-Bourez1
1
OCA – Observatoire de la Côte d'Azur, Caussol, France
2
CNES –French Space Agency, Toulouse, France
pierre.exertier@oca.eu

Abstract
The Time Transfer by Laser Link (T2L2) experiment, developed by both the Observatoire de la Côted’Azur (OCA) and the Centre National d’Etudes Spatiales (CNES), performs optical ground to spacetime transfer. Its principle is derived from laser telemetry technology with dedicated space equipment
designed to record arrival time of laser pulses at the satellite. According to the capabilities of groundlaser stations (laser operations are weather dependent) T2L2 permits to realize some links between
distant clocks with expected time stability of a few picoseconds and accuracy better than 100 ps.
The T2L2 space experiment has been launch in July 2008 on-board the oceanography satellite Jason2.
The International Laser Ranging network has been applied to track the satellite permanently, theSatellite Laser Ranging (SLR) technique being primarily used to support the precise orbit determinationof the satellite. Thanks to T2L2, this tracking permitted to link SLR observatories (most of themequipped with GPS and some of them ultra stable clocks) and to promote time synchronization withinintercontinental distances, as a service to the space geodesy community. In addition, several dedicatedcampaigns have been conducted from 2009 to 2013 to analyze carefully the T2L2 performances in termsof time stability and time accuracy, to realize some synchronization between remote ultra stable clocks
and to perform microwave time transfer comparison such as with GPS. A detailed analysis of all thesensitive elements used in the measurement chain of the ground segment was recently done in some
SLR stations in order to improve time stability and to reach the performance that was primary specified.
Through 5 years of activity supported by both CNES and OCA, this work highlights the performances ofT2L2 and tries to enlighten the community on the advantages and disadvantages of space opticaltechnique. It summarizes the results as qualitative and quantitative.

IFCS-EFTF5-G2-2

ACES MicroWave Link and Ground Segment
Hess MP, Helm A, Kehrer J, Schäfer W+, Cacciapuoti L*, Much R*, de Parolis L*
Astrium Space Transportation, Friedrichshafen, Germany+
TimeTech, Stuttgart, Germany* European Space Agency, ESTEC, Noordwijk, The Netherlands
Email: Marc-Peter.Hess@astrium.eads.net
Atomic Clock Ensemble in Space (ACES) is a mission using high-performance clocks and links to test
fundamental laws of physics in space. The ACES payload is accommodated externally on the ISS
Columbus laboratory. The ACES microwave link (MWL) will make the ACES clock signal available toground laboratories equipped with atomic clocks and outfitted with dedicated MWL Ground Terminals.
The ACES Ground Segment will perform all monitoring and control tasks of the payload as well as of
the word-wide distributed set of MWL Ground Terminals. The ACES Ground Segment collects all
housekeeping and science data generated by the payload and ground terminals. The science raw data isprocessed into higher level data products that can be retrieved by a large science community.
We will give a brief status overview on the development of the ACES payload, where the integration of
the flight model has started. The latest results obtained with the MWL will be discussed. Further we will
detail the Ground Segment and MWL Ground Terminal design, which is presently undergoing
acceptance testing with a focus on the description of the ACES science data products and underlying
algorithms.

IFCS-EFTF5-G2-3

Towards a free space satellite to ground coherent optical link
P. Wolf1, N. Chiodo1, K. Djerroud1, O. Acef1, G. Santarelli1
E. Samain2, J. Paris2, B. Fleury3, J. Montri3, C. Petit3
1
2

LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France
Géo-Azur, Observatoire de la Côte d’Azur, CNRS, Grasse, France
3
DOTA, ONERA, Chatillon, France
Email: peter.wolf@obspm.fr

Coherent links are based on the direct measurement of the optical phase rather than an amplitude
modulation (pulses) as in conventional laser ranging. A limiting factor in this kind of links is the time
variation of the refractive index of the terrestrial atmosphere due to the turbulence phenomenon that
adds phase noise and intensity fluctuations both decreasing the performance of the link. Based on first
results of a ground-ground coherent link323 with 5 km propagation through the turbulent atmosphere weestimate the potential performance of such links for ground to space frequency comparison of clocks,
showing that significant improvement with respect to existing methods can be expected, potentiallydown to 10-17 in relative frequency in less than 1000 s integration time.
Our next step towards this goal is the experimental realization of a link from a ground telescope
to a low Earth orbit (LEO) satellite equipped with corner cube reflectors. We describe the requirementson the laser system for such a link (stability at the 10 -13 level or below, whilst being tunable over 20GHz) and present our solution for that challenge showing the performance of our laser system.
We describe first (unsuccessful) experiments that took place in November 2012 and January
2013 at the 1.5 m lunar ranging telescope of the Observatoire de la Côte d’Azur in collaboration withONERA (French aerospace lab) who provides the adaptive optics bench. We discuss the encounteredchallenges and difficulties, and the implemented or planned solutions. Additional experiments will takeplace in 2013 before the conference, and depending on their outcome we might show first signals
received from the satellite.

323

K. Djerroud, et al., “Coherent Optical Link Through The Turbulent Atmosphere”, Opt. Lett.., vol. 35, p. 1479-1481, 2010.

IFCS-EFTF5-G2-4

Design of the F&T Subsystem
for ESA’s Deep Space Antenna 3
Solana, A.1, Schaefer, W.1, Schwall, T.1 , Ramos, M.2 , de Vicente, J.2,
Froidevaux, S.3 , Giordano, V. 4 , Grop, S. 5 , Dubois, B. 5
1

TimeTech GmbH, Stuttgart, Germany
ESA-ESOC, Darmstadt, Germany
3
T4Science, Neuchâtel, Switzerland
4
Femto-ST, Besançon, France
5
ULISS-ST, SAIC Université de Franche-Comté, Besançon, France
2

Email: Ainhoa.Solana@timetech.de

New concepts and techniques to try to improve the overall performance of Frequency and Timing
subsystems were developed and applied to ESA’s third Deep Space Antenna (DSA3), near Malargüe inArgentina.
Independent and well-controlled clocks room, together with an improved short term stability and phasenoise lead the way into the introduction of a 100 MHz
distribution system, maintaining the same level of
performance at both ends of the cross-site link. Lower
frequencies, such as 5 MHz and 10 MHz, were locallygenerated in each building from the 100 MHz source.
The introduction of a cryogenic cooled sapphireoscillator (in addition to the two redundant activehydrogen masers), accomplished to combine its goodshort term stability while remaining locked to one of
the masers profiting of the maser’s long-term
performance.
The performance achieved after adaptation andoptimization of the key elements of the F&T
subsystem and the reduction of the thermal sensitivity,
allowed distribution to the antenna site, at a distanceof approximately 100m.
Fig. 100: CSO (Cryogenic Sapphire Oscillator)
The system design and the results of final on-site
acceptance tests are presented.

IFCS-EFTF5-G2-5

Clock Composition by Wiener Filtering Illustrated on Two Atomic
ClocksMarek Peca1,2, Vojtěch Michálek1,2, Michael Vacek1,2
1

2

Serenum, a. s., Beranových 130, Praha – Letňany, Czech RepublicČeské vysoké učení technické v Praze, Břehová 7, 115 19 Praha 1, Czech Republic
e-mail: peca@serenum.cz

Clock ensembling, i.e. calculation of best time estimate given readings from multiple clocks, is a mustfor state-of-art timekeeping. Clock drift and jitter are usually modelled as colored noise, therefore alinear estimation is naturally the tool of choice. The crux of the matter is that unlike traditional
estimation problems, the clock ensemble is both marginally stable (drifting) and partially unobservable(only time differences are measurable). Modifications of Kalman filter estimator to handle these
conditions were made using special covariance matrix treatment324,325.
As an alternative to Kalman filter approach, a Wiener filter has been elaborated on the simplest yet
useful example of two distinct atomic clocks, motivated by ACES project 326. The resulting estimator is
structurally and computationally simpler than Kalman filter, and in case of time invariant models it isequally optimal. Design procedure is described covering clock noise modelling (including flicker
approximation), and polynomial estimator calculation, concentrated on numerical pitfalls, and common
marginally stable factors. Both non-causal(infinite lag) and causal (real-time)
estimators are discussed.
Performance of the resulting estimator issimulated based on published ACES projectmodels3. Results are plotted by means of
power spectral density (PSD) and Allan
deviation (Fig. 1), and compared to current
solution based on feedback loops. It isshown that Wiener estimator performs
better than the ACES feedback loops;
generally, better than any possible feedback
system so far. Most importantly, the system
integrated with Wiener estimator issubstantially simpler, inherently stable,
contains less noise sources, and it is optimal
up to an arbitrary roundoff error floor.

324

Fig. 101: Allan deviation of PHARAO-Cs and SHM clocks3
and Wiener filtered ensemble.

K. R. Brown, “The Theory of the GPS Composite Clock”, Proceedings of ION GPS-91, p. 223–241, 1991.

325

C. A. Greenhall, “Forming stable timescales from the Jones-Tryon Kalman filter”, Metrologia, vol. 40, no. 3, p. 335–341,
2003.
326

J. K. Dam et al, “Simulation of Servo Loops in Atomic Clock Ensemble in Space (ACES)”, 24th European Time andFrequency Forum, 2010.

IFCS-EFTF5-G2-6

Characterization of atomic clock anomalies in the dynamic Allan
variance domain
Lorenzo Galleani1, Patrizia Tavella2
1

Politecnico di Torino, Torino, Italy
2
INRIM, Torino, Italy
Email: galleani@polito.it

The stability of an atomic clock changes with time due to several factors, such as mechanical vibrations,temperature, and radiations. To represent this time variation, we introduced the dynamic Allan variance(DAVAR)327,328,329. The DAVAR is a surface function of time and the observation interval. This surface
is stationary with time when the clock follows the specifications, whereas it changes with time when an
anomaly occurs. We derive the analytic DAVAR for a series of common anomalies, namely, a phase
jump, a frequency jump, and a short duration sinusoid, that is, a sinusoid with finite time support. These
anomalies are of fundamental interest in space clocks. Our results establish a clear connection between
the nature and properties of the anomalies and the corresponding shape of the DAVAR.

327

L. Galleani, “The Dynamic Allan Variance III: Confidence and Detection Surfaces,” IEEE Trans. Ultrason. Ferroelectr.
Freq. Control, vol. 58, no. 8, pp. 1550-1558, 2011.
328

L. Galleani, “The Dynamic Allan Variance II: A Fast Computational Algorithm,” IEEE Trans. Ultrason. Ferroelectr.
Freq. Control, vol. 57, no. 1, pp. 182-188, 2010.
329

L. Galleani and P. Tavella, “The Dynamic Allan Variance,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 56,
no. 3, pp. 450-464, 2009.

MEMS Oscillators
CLUB D
Wednesday, July 24 2013, 10:30 am - 12:00 pm
Chair:

Wan-Thai Hsu
Discera Inc

IFCS-EFTF2-G3-1

Exploiting Dynamics to Achieve Tiny High-PerformanceFrequency Sources
Jeffrey L. Rogers
Microsystems Technology Office, Defense Advanced Research Projects Agency (DARPA), Arlington,
VA, USA
Email: jeffrey.rogers@darpa.mil
The traditional understanding that reductions in size and associated improvements of oscillator
performance are ultimately limited by the deleterious effects of nonlinearity and noise explain MEMS
based oscillators failing to realize their technological promise. The MEMS advantages in size, weight,
power, and integrability with CMOS have been limited to those applications where performance can besacrificed to realize these advantages. As a result, MEMS have not been useful in many important
applications that depend on performance, e.g., acquiring and tracking GPS. In light of modern advancesin dynamics and the broader breakdown of assumptions underlying these performance expectations,conventional limitations must be reassessed.
The premise of the Mesodynamic Architectures (Meso) program at DARPA is that nonlinearity andnoise inherent to all small-scale oscillators can be exploited to surpass traditional performance limits. In
particular, the Meso program seeks to achieve frequency sources with unprecedentedly low phase-noiseper-unit-device-volume. Phase noise is particularly difficult since it cannot be filtered without theoverhead of active canceling or put through a limiter without also removing oscillation signal.
Complicating the problem further is that oscillators are inherently noisy close to the characteristicfrequency and in the phase of oscillation. At the same time, dynamics offer novel mechanisms that canbe used to improve oscillator behavior. Examples include decoupling amplitude modulation from phasemodulation and tuning background fluctuations to enhance oscillator phase purity.
This talk will summarize the Meso program and provide a context for the results to be reported in thissession. The architectures being pursued include tiny beams of different materials, disks, and thin films.
Advances in the key figures of merit of phase noise and device size will be discussed along with resultsin maintaining temperature stability and acceleration stability. Potential avenues for further study will
also be discussed.

IFCS-EFTF2-G3-2

Dynamics of Microscale Thin Film AlN Piezoelectric Resonators
Enables Low Phase Noise UHF Frequency Sources
Gianluca Piazza1, Augusto Tazzoli1, Nicholas Miller1, Jeronimo Segovia1, Cristian Cassella1, Jabeom
Koo2, Brian Otis2, Kamala McNaul3, Brian Gibson3, Kimberly Turner3, Todd Palmer4
1

Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
2
Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, USA
3
Department of Mechanical Engineering, University of California, Santa Barbara, CA, USA
4
Vectron International, Mount Holly, PA, USA

Email: piazza@ece.cmu.edu
Low phase noise (PN) frequency sources from 100 MHz to 1.5 GHz rely on single crystalline
mechanical resonators such as quartz crystals and surface acoustic wave devices to form a stablereference. Despite the impressive performance, these components cannot be directly integrated withCMOS electronics, are relatively bulky and are far from attaining the ultimate size, weight and power
consumption that would be desirable for high-end commercial, industrial, and especially military
applications.
Thin film micro and nanoscale resonators
have emerged as a promising class ofdevices for the synthesis of stablefrequency
sources.
Thin
film
piezoelectrics have shown to be the only
viable transduction mechanism todemonstrate Ultra High Frequency(UHF) references. AlN contour-mode
resonators1 can provide high Q and low
motional impedance and are especiallysuited for the implementation of CMOSintegrable multi-frequency sources on asingle chip.

Fig. 102: (top) SEM figures of an ovenized thin film AlN resonator used asa frequency reference for temperature stable UHF oscillators. (bottom)
Example of how the resonator dynamics can be exploited to evade amplifier
noise for particular phase shifts in a close-loop oscillator (220 MHz carrier).

Nonetheless, the ultimate performance of
these devices is hindered by theirminiaturized dimensions, their complex dynamics and the unknown noise mechanisms associated with
it. Here we analytically and experimentally explain how the non-linear dynamics of the AlN resonators
are due to self-heating. Furthermore, we experimentally show how the dynamics of the resonator can be
exploited to evade amplifier noise and reduce the close-in PN of the oscillator. We also measure, for the
first time, the intrinsic noise of these resonators in an open-loop configuration, a particularly challenging
task at frequencies above 500 MHz, but of paramount importance in order to fully understand thelimiting mechanisms of phase noise.
With the aim of delivering temperature stable and acceleration insensitive oscillators, we introduce
geometrical variations in the resonator layout to enable low power ovenization and reduce flexural
deflections. Preliminary demonstration of UHF sources have yielded devices with PN < -94 dBc/Hz and– 160 dBc/Hz at 1kHz and 10 MHz offsets, temperature stability of 2 ppm from - 20 to + 85 ºC, andacceleration sensitivity < 30 ppb/G.

IFCS-EFTF2-G3-3

Single Transistor Oscillator Based on a Graphene-Aluminum
Nitride Nano Plate Resonator
Zhenyun Qian1, Yu Hui1, Fangze Liu2, Swastik Kar2 and Matteo Rinaldi11Dept. of Electrical and Computer Engineering, Northeastern University, Boston, MA, USA
2
Dept. of Physics, Northeastern University, Boston, MA, USA
Email: qian.z@husky.neu.edu, rinaldi@ece.neu.edu

This paper reports on the first demonstration of a high frequency (245 MHz) single transistor oscillator
based on Graphene-Aluminum Nitride (G-AlN) nano-plate resonator (NPR). For the first time, a 2dimensional (2D) electrically conductive graphene layer was integrated on top of an ultra-thin (500 nm)
AlN nano-plate and excited into a high frequency contour-extensional mode of vibration by
piezoelectric transduction (Fig.1). The resulting ultra-thin, low mass and high frequency G-AlN
nanomechanical resonator showed high values of electromechanical coupling coefficient (kt21.8%) andquality factor (Q1000) which enabled the implementation of a low phase noise (-87 dBc/Hz @ 1kHz
offset and -125 dBc/Hz floor) single transistor oscillator.
The physical and electrical properties of the metal electrodes fundamentally limit volume and frequency
scaling of conventional MEMS/NEMS piezoelectric resonators [1]. Furthermore, it has been recently
shown that metal electrode damping and interface strain are responsible for the Q limits in conventional
AlN Lamb wave resonators [2]. In this work a stepping stone towards the development of metal-freepiezoelectric NEMS resonators is set by integrating a 2D graphene electrode on top of an AlN resonantnano-plate in lieu of a relatively thicker and heavier metal electrode. Despite a bottom metal interdigitalelectrode is still employed in this first prototype, the fabricated G-AlN resonator is characterized by
reduced mass (~53%) and volume (~20%), increased sound velocity, hence resonant frequency (~36%),and improved device figure of merit (kt2Q18) compared to a conventional AlN NPR device (kt2Q12)
based on the same core design but employing a 150 nm thick gold top electrode instead of the single
atomic layer graphene. Both the G-AlN NPR prototype and the conventional AlN NPR were directly
wire-bonded to Pierce oscillator circuits implemented with an ATF-551M4 E-pHEMT GaAs transistor.
Despite the 150 fold smaller volume of the top electrode and the 36% higher operating frequency,
improved phase noise performance was recorded for the G-AlN device (Fig.2) demonstrating the great
potential of using graphene as 2D electrode in piezoelectric NEMS resonators.
[1] M. Rinaldi et al., IEEE T-UFFC, vol. 57, n. 1, pp. 38-45. [2] T. Yen et al., Proc. IEEE MEMS 2013, pp. 114-117.

Fig. 103: (a) Schematic diagram of G-AlN NPR oscillator. Fig. 2: Measured phase noise of the two(b) Picture of the G-AlN NEMS die wire-bonded to the oscillators for best bias conditions (using anoscillator printed circuit board and SEM image of G-AlN Agilent N9010A EXA signal analyzer).
NPR.

IFCS-EFTF2-G3-4

A 120-µW GSM Phase Noise-Compliant Pierce Oscillator
Referenced to a 61-MHz Wine-Glass Disk Resonator
Thura Lin Naing, Tristan O. Rocheleau, Elad Alon, and Clark T.-C. Nguyen
University of California at Berkeley, Berkeley, California, USA
Email: thura@eecs.berkeley.edu
A 61-MHz Pierce oscillator referenced to a single polysiliconsurface-micromachined wine-glass disk resonator has achieved
phase noise marks of -120dBc/Hz at a 1-kHz offset and 139dBc/Hz at far-from-carrier offsets. When divided down to
GSM’s 13MHz, this corresponds to -133 dBc/Hz at 1-kHz and 152dBc/Hz at far-from-carrier offsets, both of which satisfy
GSM reference oscillator phase noise requirements. This Pierce
oscillator not only provides improvements of 10dB at 1kHz and
7dB at far-from carrier offsets versus a transimpedance amplifier(TIA) topology330 using a similar single disk, it also reduces
power consumption down to only 120µW, which is ~3 times
smaller. Such low phase noise and power achieved by a tiny
MEMS device might soon be key enablers for low power “setand forget” autonomous sensor networks with substantial
communication capability.
Previous TIA-based oscillators1 attained GSM specs by arraying
MEMS devices to boost oscillator loop power to reduce far- Fig. 104: The 61-MHz Pierce oscillator.
from-carrier phase noise. In contrast, the work presented here
achieves the same GSM spec using only a single MEMS
resonator with significant area savings versus the previous large
array. It does this via the remarkably simple Pierce configurationof Fig.1 that yields better performance in two ways: 1) byreducing noise-figure by using only two active transistors; and 2)
by increasing voltage swing, thereby raising oscillator loop
power.
Fig. 2 compares measured phase noise data for a 61-MHz TIAbased oscillator with that of the Pierce oscillator at 61MHz (anddivided down to 13MHz), clearly showing the performancedifference, and from the 13MHz curve, clearly meeting GSM Fig. 105: Measured phase noise of 61specs. When power consumption is taken into account using the MHz oscillators and normalized to 13
popular Figure of Merit (FOM) (given in the plot inset), this MHz (Pierce) for comparison to GSM
performance marks the best FOM at 1 kHz among published on- spec.
chip oscillators to date, as illustrated in the table below.
Device Type
FOM@ 1 kHz (dB)330

This work-225

Wine-glass array1-223

FBAR331-220

Quartz332-211

Y.-W. Lin, et al., “Low phase noise array-composite micromechanical ..,” Tech. Dig. IEDM 2005, pp. 287-290.
A. Nelson, et al., “A 22µW, 2.0GHz FBAR oscillator,” RFIC 2011, pp. 1-4.
332
J. T. M. van Beek, et al., “A review of MEMS …,” J. Micromech. Microeng, vol 22, no.1, 2011.
331

IFCS-EFTF2-G3-5

A 995MHz Fundamental Nonlinear Quartz MEMS Oscillator
R.G. Nagele, H.P. Moyer, D. J. Kirby, Y. Yoon, R.L. Kubena, R.J. Joyce, P.D. Brewer
and D.T. Chang
HRL Laboratories, LLC, Malibu, CA, 90265 USA
Email: rgnagele@hrl.com
Recent work over the last few years has focused on developing methods to characterize resonatordynamics by measuring the impedance of the resonator under drive in a closed loop oscillating
system333,2. Work at HRL Laboratories has enabled the capability to measure resonators in the 500600MHz range and determine the magnitude of the admittance vs. frequency and the associated phasenoise levels.
Our work focuses on using this technique to plot the phase noise vs. frequency at a fixed drive level. The
device measured is a 995 MHz AT-cut quartz fundamental thickness-shear mode resonator. The
rectangular quartz plate dimensions are 320 m x 290 m with 100 m diameter, 0.08 m thick circularaluminum electrodes on the top and bottom surfaces of the quartz. An unloaded Q of 13,390 andmotional resistance of 67.8 ohms was measured in vacuum. This yields an fxQ product of 1.33e 13 Hz,
close to the expected limit for quartz devices. Fig. 1. shows the phase noise at a 1KHz offset for the
resonator. The minimum phase noise achieved is ~-106dBc/Hz which to our knowledge is the bestreported for a quartz resonator
operating in the fundamental
mode at this frequency.
The loop oscillator consists of a
Mini-Circuits amplifier, voltage
controlled phase shifter, voltage
controlled variable attenuator,
power splitter and a resonatorcircuit with ZIF voltage probe
connections that utilize Agilent
low parasitic differential active
probes used for measuringresonator admittance. Oscillator
output goes to a frequency
counter and phase noise analyzer. Fig.1. Plot of phase noise vs. frequency at a 1KHz offset for three different
Upon establishing an oscillation drive levels.
condition, a computer program
reads the voltage from the oscilloscope and adjusts the variable attenuator to achieve the desired voltage
drive level. The phase shifter is adjusted in 5° increment and the process is repeated until the phaseshifter reaches a state where the oscillation condition is not satisfied. Fig. 1. shows the resulting phasenoise at a 1KHz vs. frequency for three different voltage drive levels. The nonlinear drive level,
175mVrms, shows the best phase noise performance over the range of oscillation frequencies.
1

H.K. Lee et al., “Motional Impedance of Resonators in the Nonlinear Regime,” in Proc. 2011 IEEE International Frequency
Control Symposium, San Francisco, CA, USA, May 2-5, 2011, pp. 1-6.
2
H.P. Moyer et al., “Nonlinear Behavior of an UHF Quartz Resonator in an Oscillating System,” in Proc. 2012 IEEE
International Frequency Control Symposium, Baltimore, MD, May 21-24, 2012, pp. 1-5.

IFCS-EFTF2-G3-6

Special Considerations for Specifying Oscillator Components
with Resonators on the Micro/Nanoscale
Jon Lovseth1, Ted Hoffmann1, Sai Kalyanaraman2, Vadim Olen1, Jennet Volden1, Paul Opsahl1
12Advanced Technology Center, Rockwell Collins, Cedar Rapids, Iowa/USA
Government Systems Airborne Navigation, Rockwell Collins, Cedar Rapids, Iowa/USA
Email: jalovset@rockwellcollins.com

Some micro/nanoscale resonator oscillators’ phase noise and temperature stability performance isinferior to traditional quartz crystal oscillators. But, does that matter? In other areas, micro/nanoscale
resonator oscillators have demonstrated one or two orders of magnitude better performance. Measured
devices have demonstrated frequency stability under vibration and a resiliency to shock not possible intraditional-sized quartz. Certain applications may have component specifications which can be derived
differently by keeping in mind how a micro/nanoscale component will respond differently under theseenvironmental conditions.
A comparison of most important requirements for oscillator components in communication, navigation,and radar radio applications is presented. Areas of specification relief are identified related to measured
performance of micro/nanoscale oscillators. Rockwell Collins has measured developmental and COTS
MEMS/NEMS resonator oscillators as part of the DARPA Mesodynamics program. This includes
piezoelectric, piezoresistive, and electrostatic devices. Rockwell Collins has used these devices todemonstrate improved performance to existing radio hardware334.

Traditional Quartz

Fig. 106. Measured vibration sensitivity of a microscale resonator oscillator
334

J. Lovseth, et. al. “Communication and navigation applications of nonlinear micro/nanoscale resonator oscillators,” SPIE,
Baltimore, MD, 2012

Frequency Combs II
CLUB H
Wednesday, July 24 2013, 02:00 pm - 03:30 pm
Chair:

Andre Luiten
University of Adelaide

IFCS-EFTF6-H1-1

An Optical-Microwave Phase Detector for Generation of LowNoise Microwave Signals from a Frequency Comb
Maurice Lessing1, 2, Giuseppe Marra1, Helen Margolis1, Tom Brown2, Patrick Gill112

National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK
Email: maurice.lessing@npl.co.uk

Ultra-stable microwave signals generated by transferring the stability of ultra-stable lasers to themicrowave domain using femtosecond optical frequency combs could benefit applications such as radarsystems, long baseline interferometry, precision spectroscopy and telecommunication systems335.
Microwave signals at harmonics of the repetition-rate can be generated via photodetection of the pulse
train of a frequency comb, but the performance is usually limited by saturation effects in thephotodetectors. Significant improvements in phase noise have been achieved using a repetition-rate
multiplication scheme336 but long-term stable operation requires power stabilization of the laser
source337. A simple technique that can provide both ultra-low residual phase noise and long term phasedrift is the optical-microwave phase detector (OMPD) 338.
We have investigated the performance of fibre-based4
and free-space OM-PDs locked to the 80th harmonicof the repetition-rate of an Er-fibre comb. The freespace OM-PD has the advantage that it can be used atwavelengths for which no commercial PM fibre
components exist. The residual phase noise of theextracted 8 GHz signal was measured by comparing
two identical systems in each case. We present thebest performance achieved with a free-space OM-PD
to date, whilst the phase noise of our fibre OM-PD is
only 10 dB higher than the best previously reported Fig. 107: Residual single sideband (SSB) phasenoise of the generated 8 GHz signals from thefibre OM-PD results4. The limitations to the current
OM-PDs. For comparison the results achieved
performance are being investigated, and we have using commercial photodiodes are also shown.
already shown for the free-space OM-PD that thenoise between 100 Hz and 1 kHz can be suppressed by using more stable mounts. Measurements of theamplitude-to-phase conversion coefficients and the long-term performance of the OM-PDs will also bepresented.
This work is supported by the UK National Measurement System and the European Metrology Research
Programme (EMRP). The EMRP is jointly funded by the EMRP participating countries within
EURAMET and the European Union.

335

T. M. Fortier et al., Nature Photonics, 5, 425–429, 2011.

336

A. Haboucha et al., Optics Letters, 36, 3654-3656, 2011.

337

W. Zhang et al., Applied Physics Letters, 96, 211105, 2010.

338

K. Jung and J. Kim, Optics Letters, 37, 2958-2960, 2012.

IFCS-EFTF6-H1-2

Spectral purity transfer between
optical wavelengths at the 10-18 level
Nicolodi Daniele, Argence Bérengère, Zhang Wei,
Le Targat Rodolphe, Santarelli Giorgio, Le Coq YannLNE-SYRTE, Observatoire de Paris, CNRS, UPMC, 61 avenue de l’Observatoire, Paris, France
Email: daniele.nicolodi@obspm.fr
Ultra-stable lasers are a basic building block for numerous high precision experiments. Such systems
traditionally rely on stabilization by high-finesse optical cavities and typically reach their thermal-noise
fundamental limit at 2 × 10-16 fractional frequency stability. Some applications require even better
performance, most particularly optical lattice clocks, whose fundamental quantum projection noise limit
could exceed 10-17 at one second, with interrogation lasers capable of sustaining such performance339.
This has recently stimulated the emergence of new solutions for improved laser frequency stability 340.
Those approaches trade improved stability with increased complexity. Furthermore, most promisinglaser stabilization techniques are not based on ultra-stable optical cavities and are restricted to specificwavelengths by the physics of the exploited stabilization mechanism. To effectively take advantage ofthe potential of these new solutions, it is therefore of paramount importance to develop techniques forfrequency stability transfer from a single laser frequency stabilization system to any optical wavelength.
We will present a scheme for optical phaselocking through a commercial-core opticalfrequency comb based on a Erbium-doped
fiber-based femtosecond laser capable offrequency stability transfer in the 1µm – 2µm
spectral region. We demonstrate spectral
purity transfer without frequency stability
degradation from a 1062 nm master laser,stabilized by an high-finesse optical cavity,
independently characterized at the 4 × 10-16
stability level, to a 1542 nm slave laser.
Operating two independent quasi-identicalsetups measuring the phase difference between
a common pair of master and slave lasers and Fig. 108: Fractional frequency stability residualcomparing the phase difference signals from noise of the spectral purity transfer system accessed
the two setups, we demonstrate that the optical by comparing two independent quasi-identicalfrequency comb does not limit the frequency setups.
stability transfer at the 2 × 10-18 level at one second. This stability transfer capability exceeds by morethan one order of magnitude the stability any optical oscillator demonstrated to date.

339

M. Takamoto et al. “An optical lattice clock”, Nature, 435, 321, 2005.

Y. Y. Jiang et al. “Making optical atomic clocks more stable with 10 −16-level laser stabilization”, Nat. Phot., 5, 158, 2011.
M. J. Thorpe,et al. “Frequency stabilization to 6 × 10-16 via spectral hole burning”, Nat. Phot., 5, 688, 2011. T. Kessler, et al.
“A sub-40-mHz-linewidth laser based on a silicon single-crystal optical cavity”, Nat. Phot., 6, 687, 2012.
340

IFCS-EFTF6-H1-3

Optical frequency comb with an absolute linewidth of 1 Hz
S. Fang1, H. Q. Chen1, Y. Y. Jiang1, T. Y. Wang1, Z. Y. Bi1, L. S. Ma1
1State Key Laboratory of Precision Spectroscopy, East China Normal University,
3663 N. Zhongshan Road, Shanghai 200062, China
Email: lsma@phy.ecnu.edu.cn

Narrow-linewidth lasers with ultra-low phase noise and spectral purity are widely used in precision measurement
and metrology. By phase-locking an optical frequency comb to a subhertz-linewidth reference laser, each comb
line inherits the phase coherence and frequency stability of the reference laser. In recent years，several groups
have used their home made hertz or sub-hertz linewidth lasers to phase-lock optical frequency combs andinvestigated the linewidth of the comb teeth. Relative linewidth of sub-mHz to tens mHz and absolute
linewidth of a few Hz have been demonstrated1-4. In this presentation, using the techniques of collinear
self-referencing5 and cross-phase modulation6, a Ti:Sapphire femtosecond (fs) laser frequency combwith a repetition rate of 800 MHz is phaselocked to a sub-hertz linewidth Nd:YAG
laser at 1064 nm. By comparing against asecond similar Nd:YAG laser, the absolute
linewidths of optical frequency comb teeth
have been measured at 0.6~1.2 Hz over anoctave spectrum. The diagram of theexperimental setup and measurements isshown in Fig. 1.

Fig. 109: The diagram of the experimental setup andmeasurements.

1

A. Bartels, et al., “Stabilization of femtosecond laser frequency combs with subhertz residual linewidths”, Opt. Lett., vol.
29, p. 1081-1083, 2004.

2

I. Coddington, et al., “Coherent optical link over hundreds of metres and hundreds of terahertz with subfemtosecond timing
jitter”, Nature Photonics, vol. 1, p. 283-287, 2007.

3

T. R. Schibli, et al., “Optical frequency comb with submillihertz linewidth and more than 10 W average power”, Nature
Photonics, vol. 2, p. 355-359, 2008.

4

K. Iwakuni, et al., “Narrow linewidth comb realized with a mode-locked fiber laser using an intra-cavity waveguide electrooptic modulator for high-speed control”, Opt. Express, vol. 20, p. 13769-13776, 2012.

5

Y. Y. Jiang, et al., “A collinear self-referencing set-up for control of the carrier-envelope offset frequency in Ti : sapphire
femtosecond laser frequency combs”, Metrologia, vol. 42, p. 304-307, 2005.

6

D. J. Jones, et al., “Frequency comb generation using femtosecond pulses and cross-phase modulation in optical fiber atarbitrary center frequencies”, Opt. Lett., vol. 25, p. 308-310, 2000.

IFCS-EFTF6-H1-4

Microwaves generation from mode-locked Er-fiber lasers with
sub-fs-level absolute timing jitter
Kwangyun Jung, Junho Shin, and Jungwon Kim*
Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea*Email: jungwon.kim@kaist.ac.kr
Ultralow phase noise RF/microwave signal sources are important for various science and engineering
applications, ranging from precision time-frequency metrology to future electronic clocks, radar andmeasurement systems. Recently, photonic generation of ultralow phase noise microwave signals using
ultrastable cavity-stabilized CW lasers and optical frequency combs has attracted great interest.341 Also,
we have recently demonstrated that the timing jitter (>1 kHz offset frequency) from free-running modelocked fiber lasers can be engineered well below 1 fs level.342 Therefore, for applications that require
ultralow short-term (<1 ms time scale) timing jitter/phase noise microwave signals, one can directly use
a simple free-running mode-locked fiber laser without state-of-the-art ultrastable cavity references.
In this paper, we show the generation of 10-GHz microwave signals from 78-MHz free-running modelocked Er-fiber lasers with 0.49 fs absolute rms timing jitter integrated from 10 kHz to 10 MHz offset
frequency, with a single-sideband phase noise of -142 dBc/Hz at 10 kHz offset frequency. In order tomitigate the shot-noise-limited high-frequency phase noise in the optical-to-electronic conversion
process (typically limited around -140 dBc/Hz level when standard 100-MHz fiber lasers andphotodetectors are used), we synchronize a low-noise voltage-controlled oscillator (VCO, 10-GHz
dielectric resonator oscillator) to the mode-locked fiber laser using our recently demonstrated Fiber
Loop Optical-Microwave Phase Detector (FLOM-PD)343 with -157 dBc/Hz background noise. Figure 1
shows the experimental setup and the phase noise measurement results. In addition, 600-m remote
generation344 of a microwave signal from a mode-locked Er-fiber laser with 2.7 fs rms relative timing
drift for 7 hours is demonstrated.

341

T. M. Fortier et al. “Sub-femtosecond absolute timing jitter with a 10 GHz hybrid photonic-microwave oscillator,” Appl.
Phys. Lett. 100, 231111 (2012).
342

T. K. Kim et al. “Sub-100-as timing jitter optical pulse trains from mode-locked Er-fiber lasers,” Opt. Lett. 36, 4443
(2011).
3

K. Jung and J. Kim, “Subfemtosecond synchronization of microwave oscillators with mode-locked Er-fiber lasers,” Opt.
Lett. 37, 2958 (2012).
4

J. Kim et al. “Drift-free femtosecond timing synchronization of remote optical and microwave sources,” Nature Photon. 2,733 (2008).

IFCS-EFTF6-H1-5

Broadband cavities for noise analysis and filtering infrequency combs relative to the quantum limit.

opticalRoman Schmeissner1, Valerian Thiel1, Claude Fabre1, Nicolas Treps1
1

Laboratoire Kastler Brossel, Université Pierre et Marie Curie, CNRS, ENS, Paris, France
Email: nicolas.treps@upmc.fr

Balanced homodyne detection with a shaped local oscillator can extract timing information and anyother parameter of femtosecond (fs) pulses with ultimate sensitivity345. To reach best sensitivities, a laser
beam that is quantum-limited in amplitude and phase is required at lowest possible frequencies.
To filter classical noise of a 25fs, 156MHz Ti:Sa oscillator at the quantum limit, we study a passive
optical cavity of Finesse 1200 that is a low-pass filter at 100kHz. A simultaneous resonance of over
100nm FWHM and >50% transmission of power is achieved. These are currently the best values forbroadband high finesse cavities.
The effects of the cavity are studied bytransfer function measurements and balanced(homodyne) detection, a new technique forthis application. Figure 1. It compares any
signal to the shot noise limit and thus allows
for ultimate measurement precisions.
The cavity filters amplitude and phase noise.
An amplitude quantum limited comb isretrieved at >500kHz. Phase noise filtering
reduces the r.m.s. phase induced timing jitter Fig. 110: amplitude noise of the mode-locked laser
at 1s integration time by 20dB leading to a, of the cavity output b; right scale carrierscales of approx. 10 yoctoseconds (10^-23s). envelope-phase noise c; amplitude transfer functionof the cavity d, filtered phase noise accessible bybalanced homodyne detection down to radsensitivities e

Noise quadrature interconversion leads to excess noise in amplitude of the transmitted beam. We
theoretically model this effect and show that it can be exploited to detect (spectral) phase noise of any
seed with highest sensitivity. The latter can be simultaneously measured over the entire optical spectrum
covered by the cavity. A shot noise limited sensitivity is of approx.
<10^-10 rad/Hz is found.
This method is applied to reveal spectrally non-constant phase noise distributions of Ti:Sa and fiberbased comb sources.

345

B.Lamine, C.Fabre and N.Treps, Quantum improvement of Time Transfer between remote clocks, Phys. Rev. Lett. 101,
2008, 123601

IFCS-EFTF6-H1-6

Optical lattice clocks with 87Sr in a cryogenic environment

Ichiro Ushijima1,2,3, Takuya Ohkubo1,2,3, Manoj Das2,3, Masao Takamoto2,3,and Hidetoshi Katori1,2,3
1
Department of Applied Physics, Graduate School of Engineering, The University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
2
Quantum Metrology Laboratory, Advanced Science Institute, RIKEN, 2-1 Hirosawa,
Wako, Saitama 351-0198, Japan
3
Innovative Space-Time Project, ERATO, JST, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656,
Japan
Email: ushijima@amo.t.u-tokyo.ac.jp
A relative frequency stability of 10-17 has been reached by comparing two Sr optical lattice clocks1. At
this level of stability, the frequency shift due to blackbody radiation (BBR) from the room temperatureenvironment becomes a major limitation for Sr lattice clocks1,2. In order to reduce the uncertainties of
BBR shift, we have developed Sr optical lattice clocks that operate in a cryogenic environment. The
BBR shift for Sr atoms is theoretically calculated to be about 2.4 Hz at 300 K. To reach the uncertainties
of 10-18, the fluctuation and inhomogeneity of the ambient room temperature T has to be controlled towithin ΔT = 0.01 K at 300 K. As the sensitivity of BBR shift varies as T3, the uncertainties can be
decreased by cooling down the environmental temperature. At the temperature of T = 70 K, the BBR
shift reduces to 10 mHz and even with a temperature fluctuation of ΔT = 1 K, clock uncertainties of 10-18
can be reached. We can evaluate the BBR shift directly as a frequency difference of two clocks bycomparing two clocks operating at different environmental temperature.
We realize the cryogenic environment by surrounding the region for clock spectroscopy with acryogenic chamber of few cm3 in volume. In order to introduce atoms and lasers, the chamber has two
apertures with diameters of 0.5 and 1 mm. The uncertainty due to BBR shift caused by the radiation that
irradiates the atoms through these apertures can be reduced to 1×10 -18 by moving the atoms 5 mm inside
the chamber and thereby reducing the solid angle from atoms to the environment to 0.5 msr. The
cryogenic chamber is cooled down to 70 K by a Stirling refrigerator and the temperature fluctuation canbe maintained to within ΔT = 10 mK.
In this poster presentation we will discuss our cryogenic setup for two Sr lattice clocks and the latest
experimental results. By using synchronous interrogation1 and comparing two clocks, one in a cryogenic
and the other in a room temperature environment, the BBR shift can be observed as the frequency
difference of the two clocks with high stability. Comparing two clocks synchronously in a reduced BBR
environment will allow us to evaluate other systematic errors such as atomic interactions and lattice lightshifts with high precision.
＿＿＿＿＿＿＿＿＿＿＿＿
1

M. Takamoto, T. Takano, and H. Katori, “Frequency comparison of optical lattice clocks beyond the Dick limit”, Nat.
Photon. vol. 5, p. 288-292. 2011.
T. Middelmann, Ch. Lisdat, St. Falke, J. S. R. Vellore Winfred, F. Riehle and U. Sterr, “Tackling the blackbody shift in astrontium optical lattice clock”, IEEE Trans. Instrum. Meas.. vol. 60, p. 2550-2557. 2011.
2

Atom-based sensors and fundamental physics
CLUB E
Wednesday, July 24 2013, 02:00 pm - 03:30 pm
Chair:

Peter Wolf
Observatoire de Paris, CNRS, UPMCIFCS-EFTF3-H2-1

Precision gravity measurementswith atom interferometry

Guglielmo M. Tino
Dipartimento di Fisica e Astronomia and LENS Laboratory
Università degli Studi di Firenze
Istituto Nazionale di Fisica Nucleare, Sezione di Firenze
via Sansone 1, Sesto Fiorentino (Firenze), Italy
Email: guglielmo.tino@fi.infn.it
I will discuss experiments we are conducting using cold atom interferometry for precision tests ofgravitational physics. In particular, I will report on the experiment to measure the gravitational constant
G with a Rb Raman interferometer, and the one based on Bloch oscillations of Sr atoms confined in an
optical lattice for precision gravity measurements.

IFCS-EFTF3-H2-2

Atomic Magnetometry for
Biomedical and Fundamental Research
Antoine Weis1
1

Physics Department, University of Fribourg, Fribourg, Switzerland
Email: antoine.weis@unifr.ch

I will report on past and ongoing research in atomic magnetometry by our team. I will illustrate theprinciple of laser-driven magnetometers based on optically detected magnetic resonance (ODMR), andreview our use of a multi-sensor array of ODMR magnetometers for recording the dynamics of humanmagneto-cardiographic field maps346 and for detecting magnetic nano-particles. We also deploy an arrayof similar sensors (in vacuum and near a 100 kV electrode) for monitoring and controlling the spatiotemporal variations of a 1 T field in an experimental search for a neutron electric dipole moment at thePaul Scherrer Institute347.
Current work focuses on the development of vector magnetometers and the exploration of magneticallysilent magnetometers based on amplitude-, frequency-, or polarization-modulated laser light. We havedeveloped an algebraic model that describes the complex structure of the multiple resonances
encountered in silent magnetometers348, in which the magnetic resonance transitions between sublevels
are driven by second-order electric dipole interactions with the (modulated) light field. Model
predictions yield excellent agreement with specificexperimental case studies using amplitude- andpolarization-modulation, respectively. Our sensors(Fig. 1) are based on 30 mm diameter room
temperature Cs bulbs with paraffin-coated walls andhave a shot noise limited magnetic fieldsensitivity349 of 10-20 fT/Hz1/2. They are operatedusing a phase-locked feedback loop and theirabsolute accuracy is severely limited by the stability
and control of the feedback phase. In order tocircumvent systematic reading errors due to phasenoise and/or drift, we currently explore feedbackfree schemes, in which we record the free induction Fig. 111: Modular ODMR magnetometer sensor
decay of the atomic orientation and/or alignment head comprising a fiber coupler, collimation andpolarization optics, a photodetector, and rf coils.
following pulsed excitation.

346

G. Bison, N. Castagna, A. Hofer, P. Knowles, J.-L. Schenker, M. Kasprzak, H. Saudan, and A. Weis, “A room
temperature 19-channel magnetic field mapping device for cardiac signals”, Appl. Phys. Lett., 95, 173701, 2009.
347
P. Knowles, G. Bison, N. Castagna, A. Hofer, A. Mtchedlishvili, A. Pazgalev, and A. Weis, “Laser-driven Cs
magnetometer arrays for magnetic field measurement and control”, Nucl. Instrum. Meth., A611, 306-309, 2009.
348
Z. Grujic and A. Weis, “Atomic magnetic resonance induced by amplitude-, frequency-, or polarization-modulated light”,
submitted to Phys. Rev. A, 2013.
349
N. Castagna, G. Bison, G. di Domenico, A. Hofer, P. Knowles, C. Macchione, H. Saudan, and A. Weis, “A large sample
study of spin relaxation and magnetometric sensitivity of paraffin-coated Cs vapor cells”, Appl. Phys., B96, 763-772, 2009.

IFCS-EFTF3-H2-3

Testing Fundamental Physics with Microwave Cavities
Stephen R. Parker1, Moritz Nagel2, Paul L. Stanwix1, Evgeny Kovalchuk2, John G. Hartnett1,3, Eugene
N. Ivanov1, Achim Peters2, Michael E. Tobar1,
1

School of Physics, The University of Western Australia, Crawley, Australia
2Institut für Physik, Humboldt Universität zu Berlin, Berlin, Germany
3Institute of Photonics and Advanced Sensing, School of Chemistry and Physics, University of Adelaide,
Adelaide, Australia
Email: stephen.parker@uwa.edu.au
We present an overview and status update of recent experiments at The University of Western Australia
and collaborating institutions that utilize microwave frequency resonant cavities to test aspects offundamental physics.
Microwave cavities loaded with sapphire exhibit quality
factors on the order of 109 at cryogenic temperatures andwhen used as a frequency discriminating element enable
the creation of loop oscillators with fractional frequency
stabilities below 2×10-16 for integration time of 100
seconds350. We describe a modern Michelson-Morleyexperiment that uses the beat frequency of two actively
rotated orthogonally aligned cryogenic sapphireoscillators to search for orientation dependent deviationsin the speed of light. The sensitivity of the experiment isdictated by the stability of the beat frequency. Potential
variations are expressed as bounds on coefficients in theStandard Model Extension framework351 and describe
possible violations of local Lorentz invariance.
Preliminary bounds from our most recent experimentdemonstrate at least an order of magnitude improvement
over previous work.
We also discuss our most recent “light shining through awall” experiment that searches for the hidden sector Fig. 112: A dual sapphire loaded cavity
photon, a hypothetical particle that weakly interacts with mount for testing Lorentz invariance.
the photon via kinetic mixing. An empty room
temperature copper cavity and an empty cryogenic niobium cavity are separated by a barrier
impenetrable to standard photons. By actively driving the copper cavity at resonance there is apossibility that photons will mix in to paraphotons, cross the barrier and then mix back in to photons in
the cryogenic niobium cavity. By measuring the power transmitted between the two cavities a bound canbe placed on the probability of kinetic mixing between photons and paraphotons.

350

J.G. Hartnett, N.R. Nand and C. Lu, “Ultra-low-phase-noise cryocooled microwave dielectric-sapphire-resonator
oscillators,” Appl. Phys. Lett., vol. 100, no. 18, 2012.
351

V.A. Kostelecky and M. Mewes, “Signals for Lorentz Violation in Electrodynamics”, Phys. Rev. D 66, 056005, 2002.

IFCS-EFTF3-H2-4

Cold Atom Test Masses and Their Applications In Space
Nan Yu, James R. Kellogg, James M. Kohel and Robert J. Thompson
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Email: nan.yu@jpl.nasa.gov
Laser-cooled cold atoms in free fall provide ideal test masses for inertial and gravity measurements.
Cold atom-based inertial sensors have demonstrated the state-of-the-art sensitivity and stability inlaboratories. Operation of this type of sensors in space offers new ways for improved gravity
measurements. Examples of potential application in space using cold atoms as test masses include
quantum test of universality of free fall, Earth and planetary gravity measurements, and gravitational
wave detection.
In this paper, we will describe some of our exploration of using free-fall cold atoms and atominterferometry in space. Two major activities are being carried out. First, we are developing atransportable gravity gradiometer based on a dual atom interferometer accelerometer system. We haverecently modified and upgraded the laser and optics system for improvement robustness and portability.
At the same time, we have significantly improved the atom interferometer contrast and signal to noiseover our previous reports [1]. The system is designed to achieve the differential gravity measurement
sensitivity below 1x10-9 g per measurement. We will describe the latest results and discuss theirsignificance.
In parallel, JPL is developing an ISS ultra-cold atom research facility, CAL (Cold Atom Laboratory) [2].
The facility is foremost designed to be a multi-user facility for ultra-cold atom and quantum degenerate
gas research in micro gravity environment. The development of the facility and experiments to be donein the facility will also serve as a technology pathfinder for cold atom experiments in space in generaland cold atom-based matter-wave interferometers in particular. We will briefly introduce the CAL
project, its science objectives, the facility design and configuration, as well as report of its development
and progress.
[1] “Development of a Transportable Quantum Gravity Gradiometer for Gravity Field Mapping,” James M.
Kohel, Robert J. Thompson, James R. Kellogg, David C. Aveline, and Nan Yu, The eighth annual NASA Earth
Science Technology Conference (ESTC2008), University of Maryland University, June 24-26. 2008;“Development of a Quantum Gravity Gradiometer for Gravity Measurement from Space,” Nan Yu, James M.
Kohel, James R. Kellogg, and Lute Maleki, J. Appl. Phys. B. 84, 647 (2006).
[2] CAL – Cold Atom Laboratory website: http://coldatomlab.jpl.nasa.gov.

Time Scales
CLUB D
Wednesday, July 24 2013, 02:00 pm - 03:30 pm
Chair:

Dirk Piester
PTB

IFCS-EFTF5-H3-1

Timekeeping Advances in Russian Federation
and Time Reference Frame for GLONASSS.Donchenko1, S.Revnivykh2, I. Blinov1, N.Koshelyaevsky1, V.Palchikov1
1

The Main Metrology Center of the State Time and Frequency Service
FSUE “VNIIFTRI,” Mendeleevo, Moscow region, Russia
email: nkoshelyaevsky@vniiftri.ru
2
Information-Analytical Centre
FSUE “TSNIIMASH,” Korolyov, Moscow region, Russia

The new national time and frequency standard (NTFS) of Russian Federation in pursuance ofDecree No. 1226 28 December 2012 of Federal Agency on Technical Regulation and Metrology havebeen commissioned. Along with it new realization of atomic time scale TA(SU) based on new timealgorithm [1] have been introduced on MJD 56289 – 28 December 2012 [2].
Composition of the new NTFS consists of:Primary CS standards for national realization of the SI time unit;
Clocks comparison and time keeping instrumentations;Time and frequency transfer and dissemination instrumentations;
Infrastructure

According to ICD GLONASS [3] national time scale of universal coordinated time UTC(SU) is
the reference time frame for GLONASS.
The paper will deliver detailed information on above mention NTFS components, theirperformances including time links between NTFS and GLONASS synchronizer, results of investigations
and time scale comparisons relative TAI and UTC.
References
1. Koshelyaevskiy N., Maslennikova M., Sokolova O., The new time algorithm for nationaltime scales of Russian Federation, Proceeding of the 6th International Symposium“Metrology of Time and Space”, 17-19 September 2012, Morozovka Holiday Hotel,
Mendeleevo.
2. On time unit changes in Atomic Time Scale TA(SU), Bulletin G-136, NOTIFICATION, ISSN
0135-2415, The Main Metrology Center of the State Time and Frequency Service, 3November 2012, Mendeleevo.
3. Global navigation satellite system GLONASS, Interface Control Document, Navigational
radiosignal in bands L1, L2, Edition 5.1, Moscow, 2008.

IFCS-EFTF5-H3-2

The New UTC(OP) based on the LNE-SYRTE
Atomic Fountains
G. D. Rovera, M. Abgrall, S. Bize, B. Chupin, J. Guéna, Ph. Laurent, P. Rosenbusch, P. Uhrich
LNE-SYRTE, Observatoire de Paris, UMR CNRS 8630, UPMC, Paris, France
Email: daniele.rovera@obspm.fr
The generation of a timescale by steering a H-maser signal to the average of all SYRTE commercial
clocks has been tested for a few years352. After running this time scale in parallel with the official
UTC(OP) which is based on one single commercial Cs clock, we concluded that the performances were
not justifying the complexity of the system. Instead, we have developed a very simple new algorithm forthe steering of a H-maser signal to the SYRTE atomic fountain ensemble (comprising 3 Cs primary
frequency standard and one Rb fountain). Preliminary tests of the new algorithm started in December
2011. For these tests we used a new 100 MHz micro phase stepper developed by SKK Electronics incollaboration with the SYRTE2. The results were very promising so that in October 2012 we
implemented the new algorithm to generate the official realization of UTC(OP).
At SYRTE all fountains share the same cryogenic oscillator which is phase locked to a H-maser. Thisway, all fountains measure the frequency of the same H-maser. Automatic fountain data processing
provides preliminary data corrected of all systematic frequency shifts, hourly. At the present stage, thedaily steering to this data-stream is sufficient to drive the new UTC(OP) with a stability in the low 10-16.
Where previously a few tens of ns were observed, the difference between UTC(OP) and UTC has notexceeded 5 ns since the implementation of this new UTC(OP).

352
2

M. Abgrall, P. Uhrich, and D. Valat, “Ongoing improvements of ...”, Proc. of the 24th EFTF 2010

D. Rovera, M. Abgrall, and M. Siccardi, “Characterization of an auxiliary ...”, Proc. 26th EFTF 2012

IFCS-EFTF5-H3-3

A new weighting procedure for UTC
Gianna Panfilo, Aurélie Harmegnies
International Bureau of Weights and Measures (BIPM)
Pavillon de Breteuil, 92312, Sèvres, France
Email: aharmeg@bipm.org

Three main algorithms are used in the generation of UTC: the prediction and the weighting algorithms tocalculate the free atomic time scale (EAL) and the steering algorithm to steer the EAL frequency on the
SI frequency provided by the Primary Frequency Standards.
The clock frequency prediction method has been reviewed and changed in September 2011 353 withsignificant effects in terms of improvement of the EAL stability. As aimed, the frequency drift affecting
EAL has almost completely disappeared after the introduction of the new prediction algorithm. However
the distribution between H-masers and caesium clocks on the total weight did not change because thefrequency prediction does not influence the weighting procedure which considers the difference [EALclock] as the relevant weighting parameter. In particular in the current weighting algorithm the inverseof the variance of the frequency of [EAL – clock] over one year is used to estimate the performance of
the atomic clocks and to assign a weight. The long term performance of the time scale is guaranteed byde-weighting those atomic clocks presenting a frequency drift (case of H-masers) or an aging. One
consequence of this procedure was the low impact of the contribution of the H-masers in the time scaleensemble.
This paper presents a new version of the weighting algorithm, supported on the concept of weighting theclocks according to their predictabilities. In this case, only the difference between the reading of theclock and its prediction is used. The main idea is that a clock with strong signatures like frequency drift
or aging can be correctly used in the timescale ensemble if well predicted.
In the new weighting algorithm the difference between the predicted and the real frequency of theatomic clocks is evaluated. A filter over one year of these data is applied to evaluate the weights and toguarantee the long term stability of the clock ensemble.
The effect of the new weighting model on the EAL stability is presented. A frequency stability
improvement of the time scale at short and long term is observed, as well as a better clock weight
distribution that allows the H-masers to play a very important role on the time scale.

353

G. Panfilo , A. Harmegnies, L. Tisserand, “A new prediction algorithm for the generation of International Atomic Time”,
Metrologia, vol. 49, n°1, pp. 49-56, 2012.

IFCS-EFTF5-H3-4

Reconstruction of UTC (NIM)
Aimin Zhang, Yuan Gao, Kun Liang, Weibo Wang, Zhiqiang Yang, Dayu Ning
Time and Frequency Division, National Institute of Metrology, Beijing, China
Email: zhangam@nim.ac.cn
Abstract
NIM has reconstructed UTC (NIM) since 2010 at new campus, and the official UTC (NIM) was
switched to the new campus in October 2012. The new clock ensemble includes 6 Hydrogen masers and7 Cesium clocks, with 1 Hydrogen maser and 2 Cesium clocks placed at the old campus. The masterclock is a Hydrogen maser at new campus, and UTC (NIM) is generated from a microphase stepper
steered by a new algorithm and UTC, the frequency of the Hydrogen maser is predicted and rapid UTC
data is used to steer UTC (NIM). A dual mixer time difference measurement system is used to measure
the time difference between the clocks and UTC (NIM) at new campus, the clocks at old campus arelinked to UTC (NIM) by GPS. GPS and TWSTFT data are reported to BIPM everyday automatically.
The GPS receivers at new campus are calibrated with reference to one GPS receiver calibrated by
BIPM. The UTC (NIM) has been operated normally at new campus, the accuracy and stability are
improved. In this paper the generation of new UTC (NIM) is described and the performance of UTC(NIM) is presented.

IFCS-EFTF5-H3-5

Methods for predicting corrections for polish time scale UTC(PL)using GMDH neural networksŁukasz Sobolewski1
1

Institute of Electrical Metrology, University of Zielona Góra, Zielona Góra, Poland
Email: sobolewski.l@gmail.com

The problem of maintaining the best compliance of the UTC(PL) with UTC is due to the complexityof calculating the UTC scale354. Consequently, this leads to a delay in issuing the BIPMs "Circular T"
bulletin, which contain the corrections for the UTC(PL) relative to UTC. In order to ensure the bestcompatibility of the UTC(PL) with UTC the prediction of the corrections is required, which may be
carried out based on analytical methods or neural networks (NN). Central Office of Measures (Główny
Urząd Miar, GUM), which is responsible for the implementation of UTC(PL), carry out the prediction of
the correction values using the linear regression method. However, this method is very labor intensive
and requires a lot of experience of the person performing the analysis.
The Institute of Electrical Metrology of University of Zielona Góra, in collaboration with GUM, is
working on predicting the corrections for UTC(PL) using neural networks (NN). The obtained results
indicate the possibility of using MLP, RBF and GMDH neural networks355. The disadvantage of MLP
and RBF networks is a need to select the number of neurons in the hidden layer in the training process,for the prediction in the given month in order to achieve the result of the prediction with a sufficientlevel of accuracy. A disadvantage of this type of NN was eliminated using GMDH neural networks(Group Method of Data Handling), belonging to the group of self-organizing networks. Preliminary
studies for a period of 5 months showed that the GMDH networks are good in task of predicting thecorrections for the UTC(PL). The results of these research was presented in the journal356.
The article will present the extended results for the period of 28 months on predicting thecorrections for the UTC(PL) using GMDH neural networks based on two methods: time series analysis
and regression. A better method of predicting the corrections for the UTC(PL) has proven to be amethod of time series analysis. The obtained results of prediction error does not exceed the value of ± 16
ns, and are much smaller than the results received in GUM.
Currently the BIPM is working on a “UTC Rapid” project. The main goal of the project is to
publish more frequently corrections for UTC(k) relative to UTCr for national time scales. Corrections
are designated for each day and published once a week. A few days delay in publishing the corrections
was decisive in the initiation of research on predicting the corrections for the UTC(PL), using GMDH
neural networks, based on previous known values of UTCr – UTC(PL) corrections. The results ofpreliminary studies indicate that it is possible to predict the corrections for the UTC(PL) based on Rapid
UTC data. The application of GMDH neural networks makes it possible to obtain predicted correction
value, which differs only to a few ns, to UTCr – UTC(PL) correction value read from BIPMs ftp server.

354

BIPM Annual Report on Time Activities, Vol. 6, Sevres, BIPM 2011.
Miczulski W., Sobolewski Ł., Application of the GMDH neural networks in prediction of corrections of the national timescale; Elektronika: Konstrukcje, Technologie, Zastosowania, nr 6, 2011, s. 45-47.
356
Miczulski W., Sobolewski Ł., Influence of the GMDH neural network data preparation method on UTC(PL) correction
prediction results, Metrology and Measurement Systems, Vol. XIX, No. 1, 2012, pp. 123-132.
355

Vapor Cell Clocks and Magnetometers
CLUB E
Wednesday, July 24 2013, 04:30 pm - 06:00 pm
Chair:

Christoph Affolderbach
University of Neuchatel

IFCS-EFTF3-I1-1

Pulsed Optically Pumped Rb Standard:a high stability vapor cell clock.
Filippo Levi, Claudio Calosso, Aldo Godone, Salvatore Micalizio
Optic Division, INRIM, Torino Italy.
Email: f.levi@inrim.it
We have realized a prototype of a Rb vapor cell clock based on pulsed operation, where opticalpumping, microwave excitation and optical detection of the transition signal are separated in time1.
Besides suppressing the laser induced light shift, the pulsed operation allows a full optimization of thelaser parameters both in the pumping and in the detection stages, where different power levels are
required.
A short term frequency instability of 1.7  10 13 1 / 2 was measured, together with a long term frequency
drift below 10-14/day. The drift is thought to be due to a residual sensitivity to environmental parameterslike temperature, atmospheric pressure and humidity. In fact subsets of the recorded data achieve
medium term stability of 2  10 15 at 104 s.
We conducted in depth analysis of the various noise sources affecting our prototype both on the longand on the short term, identifying possible avenue to improve the clock stability.
Among others, the Dick effect and the laser detection noise are the most important sources of frequency
instability on the short term, while the shape of the cell is demonstrated to affect the temperaturesensitivity of the system.

Overlapping Allan deviation

In the talk we will present the most recent experimental results and we will discuss the ultimate stability
that can be achieved by this pulsed frequency standard.

Total Allan Deviaiton

1E-13

1E-14

1E-15

1E-13

1E-14

1E-15
1

10

100

1000

10000

1000001000000

1

Time /s

10

100

1000

10000

Time /sFig. 1 - Allan deviation of the prototype: typical results (left) and a data subset (right)

1

This work was funded by ESA, ESTEC contract 21504/08/NL/GLC

IFCS-EFTF3-I1-2

Study of an observation method based on Crossed
Polarizers for High-contrast Coherent Population Trapping
Yuichiro Yano, Shigeyoshi Goka
Graduate School of Science and Engineering, Tokyo Metropolitan University,
Hachioji, Tokyo 1920397, Japan
Email: yano-yuichiro@ed.tmu.ac.jp
We proposed an observation method based on crossed polarizers for obtaining high-contrast coherent
population trapping (CPT) resonance with parallel linearly polarized light (lin||lin field). Experimentresult shows that high resonance contrast (88.4%) can be observed using a 133Cs gas cell and the D1-line
vertical-cavity surface-emitting laser (VCSEL).
Figure 1 shows an optical system of the proposedlin || linBobservation method. A single-mode VCSEL was133
used to excite Cs at the D1-line. The VCSEL
PhotoCs+Ne cell
VCSEL
diode
was driven by a dc injection current using a bias T
and modulated at 4.6 GHz. The cylindrical gas cellwas 20 mm long and contains a mixture of Cs
1st Polarizer
2nd Polarizer
atoms and 4 kPa of Ne buffer gas at a controlledtemperature, and was placed at a static magnetic Fig. 113: Optical system for observing CPT
resonance.
field of 93.0 μT. Two polarizers were placed on
both sides of the gas cell, and these transmission
axes were set nearly orthogonal to each other. A
parallel linearly beam was incident on the gas cellby the first polarizer.
The polarization of wavelength components which
excite CPT is rotated by Faraday effect after
passing through the cell357. On the other hand, thepolarization of wavelength components which do
not excite CPT is not rotated. Therefore, thesecond polarizer blocks the not-exciting CPT
wavelength components incident on a photodiode. Fig. 114: Measured CPT resonance. Center
As a result, the photodiode DC current can be frequency was 4.596 GHz.
reduced because the unwanted wavelengthcomponents incident on the photodiode decreases, thus, high-contrast CPT resonance can be obtained.
The measured CPT resonance with our method is shown in Fig. 2. When the transmission axis of second
polarizer was optimized, the contrast of 88.4% was achieved. As a contrast with a conventional lin||linmethod was 3.3%, the contrast with our method was about 25 times better than that with theconventional method.
Since our optical system is very simple, this method has the potential to be powerful tool for enhancing
frequency stability of CPT atomic clocks.
357

P. M. Anisimov, R. A. Akhmedzhanov, I. V. Zelensky, and E. A. Kuznetsova, Journal of Experimental andTheoretical Physics, Vol. 97, No. 5, 2003, pp. 868–874.

IFCS-EFTF3-I1-3

Frequency Stability Performance of a Laser Pumped Rubidium
Vapor Cell Atomic Frequency Standard
Miao Zhu
Agilent Laboratories, Agilent Technologies, Santa Clara, CA, USA
Email: miao_zhu@agilent.com
The AC Stark shift (the light shift) is very important in the performance of laser-pumped vapor cellatomic frequency standards, both in the population-altering-pumping (PAP) configuration and in thecoherent-population-trapping (CPT) configuration. A continuous wave population-altering-pumping
method with reduced light shift was proposed and implemented [1, 2]. Because there is no opticalswitch (such as an acousto-optical modulator) required, this method can be implemented in a compact
vapor cell atomic frequency standard.
Here we report the frequency stability performance of a rubidium vapor cell atomic standard using thisPAP method. In the setup a microwave cavity/oven assembly contained a 87Rb cell (inner diameter ~8.5 mm, inner length ~ 13.5 mm). A diode laser with a wavelength of 795 nm was used for opticalpumping. The laser frequency was stabilized to the 87Rb transition (F = 2 → F’ = 1 & 2) using theinjection current to the diode laser while the slow change of the laser power was corrected using thelaser temperature. In addition, the transition frequency between the states |F = 1, mF = 1> and |F = 2, mF= 1> was used to adjust the bias magnetic field.
The device has been operating for more than 240 days continuously. The short term frequency stability
data shows y() < 3×10-12 s-1/2. Figure 1 shows that the absolute value of the relative frequency(averaging time = 1000 s) is smaller than 2.5×10-12. The updated results will be reported at theconference.

Relative Frequency (1012)

30
20
10
0
-10
-20
-30
0

50

100

150

200

250

Time (day)Fig. 1 Relative frequency (averaging time = 1000 s) vs. time. See the text.
References:[1] Miao Zhu, 2007 Joint Meeting of IEEE Frequency Control Symposium and European Frequency andTime Forum, page 1334.
[2] Miao Zhu and Jeffrey F. DeNatale, 2009 Joint Meeting of IEEE Frequency Control Symposium andEuropean Frequency and Time Forum, page 1183.

IFCS-EFTF3-I1-4

The Influence of Laser Polarization Noise on the Short-Term Stability of CPT Atomic Clocks

James Camparo, Michael Huang, and Travis Driskell
james.c.camparo@aero.org
Physical Sciences Laboratories
The Aerospace Corporation, 2310 E. El Segundo Blvd., El Segundo, CA, 90245, USA
The Coherent-Population-Trapping (CPT) vapor-cell atomic clock represents a clear break fromprevious vapor-cell clock technology. Beyond its already demonstrated utility for clock miniaturization,
the underlying physics of CPT has advantages that may result in significant frequency stability
improvements; for example, without a microwave cavity there is no sensitivity to microwave cavity-Q
variations. However, along with the technology’s benefits come new effects that may limit the CPT
clock’s capabilities, and one such effect is laser polarization noise. In the typical CPT clock, rightcircularly polarized light (for example), +, creates a superposition state composed of the two mF = 0
ground state sublevels of an alkali atom via a common mF = +1 excited state. If the polarization
suddenly changes to left-circularly polarized light, , and back again, the common excited state willchange from mF = +1 to mF = 1 and then back to mF = +1. This will introduce a transient in the CPT
signal, and thereby a degradation of the CPT clock’s signal-to-noise ratio, S/N.
In previous work, we showed that when an atom interacts with a polarization modulated field, the CPT
signal will first increase in amplitude as the polarization switching decreases the vapor’s electronic spinpolarization (i.e., the atomic density in the “trapping state”), and then the CPT signal will split into adoublet as the rate of coherence modulation becomes larger than the natural CPT linewidth.
Here, we consider the problem of the CPT signal and noise when the laser polarization switches
randomly. Specifically, in our experiments the laser polarization is characterized by a binomial process,as might be the case for VCSEL diode lasers, and we measure the CPT-signal amplitude, the CPT-signal
linewidth, CPT, and the CPT-signal noise level at low Fourier frequencies (i.e., ~ 102 Hz): S/N and Q =hfs/CPT. Based on these measurements, we then infer the short-term stability of a CPT clock subject toa laser undergoing stochastic polarization variations: (QS/N)-1.
For a CPT clock based on the traditional excitation scheme (i.e., use of right or left-circularly polarized
light), the large transients in the transmitted light intensity following a polarization change (which result
from a bulk motion of atomic population among Zeeman sublevels) yield a degradation in the CPT
clock’s short-term stability, even for relatively rare polarization switching events. Alternatively, for
CPT clock’s based on more novel excitation schemes (i.e., essentially the use of right and left-circularly
polarized light) we anticipate only a modest change in short-term stability, which results from a small
increase of the CPT-signal’s linewidth. Thus, in addition to producing significantly larger CPT atomic
clock signals, these more novel CPT signal excitation schemes may be less sensitive to laserpolarization noise.

IFCS-EFTF3-I1-5

A push-pull magnetometer
E. Breschi1, Z. Grujic, P. Knowles, and A. Weis
1

Physics Department, University of Fribourg, Switzerland
Email: evelina.breschi@unifr.ch

We report on an experimental study of a "push-pull magnetometer" based on polarization modulation.
Although originally proposed to increase the resonance contrast in atomic clocks358, the push-pull
technique can be applied to a variety of interaction schemes. The fundamental concept behind push-pullis to drive a beat resonance between magnetic sublevels with modulated light, whose modulation isphase-coherent with the dynamic
evolution of the atomic quantum state.
In the experiment, the laser
polarization is modulated at a fixed
frequency (mod between 100 Hz and
10 kHz). The laser frequency is
actively stabilized on the Fg=4 →Fe=3
D1-transition in cesium via a Dopplerfree DAVLL. The atoms are confinedin an evacuated paraffin-coated cellmaintained in a controlled magnetic
field, of which one Cartesiancomponent is scanned, while the two Fig. 1: Magnetic field dependence of dispersive lock-inothers are carefully compensated to signals for q=2,4,6, and 8, where q indicates the modulation
zero. Light transmitted through the frequency harmonic used for lock-in detection. Dots arecell is collected by a photodiode measurements and the red-line shows model results. All
whose signal is demodulated by a spectra are normalized to the amplitude of the (q=2, m=1)lock-in amplifier referenced to a resonance.
harmonic q of mod.
We study spectra obtained by lock-in detection under different polarization modulation configurations.
Figure 1 shows the results for a square-wave modulation between left- and right-circular polarizations,with the magnetic field component orthogonal to the laser propagation vector being scanned.
Resonances are observed whenever m·mod = L. An algebraic model359 describing the dynamics ofatomic spin orientation has been used for data interpretation. Experimental results and model predictions
are in excellent agreement. The dispersive lock-in signal can be used as an error signal for magnetic
field measurements. In order to evaluate the sensitivity of the push-pull magnetometer, we estimate thenoise-equivalent-magnetic field360 defined as the ratio between photocurrent’s shot noise, and thereference resonance discriminator slope. Different harmonic signals can be considered and compared formagnetic sensitivity.

358

Y.-Y. Jau, E. Miron, A. B. Post, N. N. Kuzma, and W. Happer ”Push-pull Optical Pumping of pure superpositions states”
Phys. Rev. Lett. vol. 93 p. 160802, 2004.
359

Z. Grujic, and A. Weis, “Atomic magnetic resonance induced by amplitude-, frequency-, or polarization-modulated light”,
submitted to Phys. Rev. A, 2013.
360

G. Di Domenico, H. Saudan, G. Bison, P. Knowles, and A. Weis, “Sensitivity of double-resonance alignment
magnetometers”Phys. Rev. A. vol. 76 p. 023407, 2007.

Liquid Sensing
CLUB D
Wednesday, July 24 2013, 04:30 pm - 06:00 pm
Chair:

Sylvain Ballandras
frec|n|sys SAS

IFCS-EFTF4-I2-1

Probing colloid-substratum contact stiffness by acoustic sensing
in a liquid phase
Adam L.J. Olsson,1 Henny C. van der Mei,1 D. Johannsmann2,
Henk J. Busscher,1 Prashant K. Sharma1
1

Department of Biomedical Engineering, University Medical Center Groningen and University ofGroningen, P.O. Box 196, 9700 AD Groningen, The Netherlands.
2
Institute of Physical Chemistry, Clausthal University of Technology, D-38678 Clausthal-Zellerfeld,
Germany
Email: johannsmann@pc.tu-clausthal.de
In QCM, particles adhering to a sensor crystal are perturbed around their equilibrium positions, via
thickness-shear vibrations at the crystal’s fundamental frequency and overtones.xvi The amount ofadsorbed molecular mass is measured as a shift in resonance frequency. In inertial loading, frequency
shifts are negative and proportional to the adsorbed mass, contrasting to “elastic loading” whereparticles adhere via small contact points. Elastic loading in air yields positive frequency shifts according
to a coupled resonance model. We here explore the novel application of a coupled resonance model for
colloidal particle adhesion in a liquid phase theoretically and demonstrate its applicability
experimentally. Particles with different radii and in absence and presence of ligand-receptor binding
showed evidence of coupled resonance. By plotting the frequency shifts versus the QCM-D overtone
number, frequencies of zero-crossing could be inferred indicative for adhesive bond stiffness. As anovelty of the model, it points to a circular relation between bandwidth versus frequency shift, with radii
indicative of bond stiffness. The model indicated that bond stiffness for bare silica particles adhering on
a crystal surface is determined by attractive Lifshitz-Van der Waals and ionic-strength-dependent,
repulsive electrostatic forces. In presence of ligand-receptor interactions, softer interfaces develop thatyield stiffer bonds due toincreased contact areas. In
analogywithmolecular
vibrations, the radii of adhering
particles strongly affect theresonance frequencies, whilebond stiffness depends onenvironmental parameters to alargerdegreethanforFig. 115: Adsorbed particles give rise to a “coupled resonance”. Whenmolecular adsorption.
Frequency and bandwidth are displayed in a polar diagram, the radius of thisdiagram is proportional to the stiffness of the link.

IFCS-EFTF4-I2-2

Sensor Design and Characterization Method for
New Multimode Downhole Sonic Measurements
Hiroshi Hori1, Yuichiro Wada1, Hiroshi Nomura1, Atsushi Oshima1,
Tadashi Tajima1, Junko Fujikawa1, Takeshi Fukushima1
1

Sonic Product Line, Schlumberger K.K., Sagamihara, Kanagawa/Japan
Email: hori1@slb.com

Downhole sonic measurements provide compressional and shear wave propagation speeds of formation
for hydrocarbon exploration purposes. Recorded data is combined with other logging data to fully
characterize the formation and wellbore for safe and effective well placement. Such information isvaluable when provided during the early stages of well placement, such as during drilling. The demand
for logging while drilling (LWD) is increasing.
Conventional LWD sonic tools are equipped with monopole transmitters and array receivers as sensors.
Receiver elements are distributed on the tool collar along the axial direction at a controlled distance. The
transmitter excites acoustic pulses in borehole fluid. Acoustic waves are radiated into the formation, anda part of the energy propagates along the tool near the wellbore and is refracted back to the borehole.
Refracted waves are recorded as the time-domain signals and processed downhole to provide formation
velocities using semblance method. The problem in shear velocity measurements occurs when formation
shear velocity is smaller than that of well fluid because refracted wave ceased to present. In suchcondition as the alternative method, we excite higher-order borehole modes, such as dipole andquadrupole, from which the shear velocity is obtained using model-based inversion techniques.
To realize new multimode measurements, we designed transmitters and receivers that consist of
azimuthally segmented units. Azimuthal transmitter output and receiver sensitivity matching is criticalto provide quality multimode measurements, especially in an acoustically challenging environment
where unwanted mode rejection is necessary.
We characterized receivers mounted on sonic tools using our in-house test facility. To ensure
measurements downhole, we recorded signals up
to high pressure and temperature of 172MPa and
150oC and normalized them using azimuthal
average. Normalized amplitude is representativeof the sensitivity matching. Figure 1 shows the
distribution of normalized signal amplitude of thereceivers over 500 elements. We concluded thestandard deviation of receiver sensitivity was 2%.
In summary, we designed the sensor for new
multimode sonic measurements while drilling,
established their characterization methods at high Fig. 116: Histogram of normalized signal amplitude
pressure and temperature, and demonstrated good of downhole sonic receivers under high pressure andsensor matching.
temperature, representing sensitivity distribution.
The standard deviation was 2%.

IFCS-EFTF4-I2-3

Analysis of the Detection of Organophosphate Pesticides in Aqueous
Solutions Using Polymer-Coated SH-SAW Sensor Arrays
Tian Newman, Arnold Mensah-Brown, Florian Bender, Fabien Josse
Dept. of Electrical and Computer Eng., Marquette University, Milwaukee, WI 53201-1881
email: fabien.josse@mu.edu
The presence of hazardous contaminants, including pesticides, in the environment continues to be ofgreat concern to public health. Among the class of pesticides, the agro-industry has increasingly reliedon organophosphate and carbamate pesticides because of their high insecticidal activity and relatively
low persistence in the environment. However, recent research shows that organophosphate pesticides(OPs) still persist in the environment for long enough to produce residues in ground water, soil, andagricultural products. The presence of OPs in surface and ground water is a major concern to publichealth. As a result, there is a need to monitor these environmental contaminants in water. The use oforganophosphates indoors has been discontinued but monitoring the output in industrial and agricultural
setting has continued. Current means of detection still require transportation to a laboratory for analysis,
resulting in costly and time consuming procedures. Therefore, there is a need for a portable and low-cost
sensor system for real-time detection, identification and quantification of organophosphates pesticides ingroundwater. In this work, the coated shear horizontal surface acoustic wave (SH-SAW) device isinvestigated as a micro-chemical sensor for the direct, rapid and in-situ monitoring of chemical
contaminants in groundwater and wastewater. The chemical contaminants being tested here areorganophosphate-based compounds (parathion, parathion-methyl, and paraoxon). The polymers used as
partially chemically selective coatings on the SH-SAW devices are 2,2’-diallylbisphenol A - 1,1,3,3,5,5hexamethyltrisiloxane (BPA-HMTS), 2,2’-diallylbisphenol A - polydimethylsiloxane (BPA-PDMS),
and polyepichlorohydrin (PECH).
An array of sensors consisting of devices with the different coatings and coating thicknesses (0.25μm
and 0.50μm) is designed to increase frequency sensitivity and selectivity by providing a specificresponse pattern for each analyte. Analyte identification is performed using a visual pattern recognition
technique based on radial plots for the analytes, parathion, paraoxon, and parathion-methyl, atconcentrations from 0.5mg/L to 3.0mg/L. These specific radial plots are made using the steady-state
frequency shifts and time responses of BPA-HMTS, BPA-PDMS, and PECH at a thickness of 0.5μm as
the axes, providing a total of six parameters for analyte recognition. It is demonstrated that each analyte
can be identified within the above concentration range using this approach. In addition, level-ofconfidence calculations are presented to estimate the concentration of an unknown sample byquantifying the similarity between known response patterns and the response pattern of the unknown
sample. It is shown that this method can successfully estimate the concentrations of measured test
samples (e.g. 3.0mg/L of parathion, 2.0mg/L of paraoxon, 0.5mg/L of parathion-methyl) and extrapolate
response patterns for sample concentrations that were not included in the pattern recognition design
database (e.g. 1.49mg/L of parathion and 1.75mg/L of parathion). It was noted that the highest levels ofconfidence for the latter test sample were found for 1.5mg/L and 2.0mg/L, giving identical level-ofconfidence values for these concentrations, thus indicating the algorithm correctly identifies the test
sample as 1.75mg/L of parathion. In summary, using the absorption time constant, which is unique to agiven analyte-coating pair, in conjunction with steady-state frequency shifts permits direct identificationand quantification of organophosphate pesticides in liquid-phase at low-ppm and sub-ppm
concentrations.

IFCS-EFTF4-I2-4

Resonant Characteristics of Rectangular Hammerhead
Microcantilevers Vibrating Laterally in Viscous Liquid MediaJinjin Zhang1, Fabien Josse1, Stephen M. Heinrich2, Oliver Brand3,
Isabelle Dufour4, Nicholas Nigro2
1
Electrical and Computer Engineering, Marquette University, Milwaukee, WI/USA
Civil, Construction and Environmental Engineering, Marquette University, Milwaukee, WI/USA
3
School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA/USA
4
Université de Bordeaux, IMS Laboratory, Talence, France
email: fabien.josse@marquette.edu
2

Dynamically driven prismatic microcantilevers excited in the in-plane direction have been investigatedand used in liquid-phase sensing applications due to their relatively high frequency stability and mass
sensitivity. However, in bio-chemical sensing applications, the performance of prismatic
microcantilever-based sensors is restricted due to their limited surface sensing area. The higher stiffness
in shorter and wider prismatic microcantilevers also makes them difficult to excite whenelectrothermally driving the sensor devices near the base. Thus, in order to increase the surface sensing
area, further improve sensor characteristics (increase the adsorbed mass and the sensitivity of detection)and make microcantilevers easier to excite electrothermally, it has been proposed to investigate
rectangular hammerhead microcantilevers driven in the in-plane flexural vibration mode in viscous
liquid media. In this work, the resonant characteristics of rectangular hammerhead microcantilevers
vibrating in the in-plane vibration mode in viscous liquid media are investigated. The rectangular
hammerhead microcantilever consists of a stem and a head. The stem is modeled as an Euler-Bernoulli
beam while the head is modeled as a rigid body. As the microcantilever vibrates, both translational androtational motions of the head are taken into account. A semi-analytical expression for thehydrodynamic function in terms of the Reynolds number and aspect ratio, h/b (thickness over width) is
first obtained. Using this expression, the resonance frequency and quality factor are investigated asfunctions of both the rectangular hammerhead microcantilever geometry and liquid media properties.
Analyses are performed and results are compared for the resonant characteristics of rectangularprismatic and hammerhead microcantilevers laterally vibrating in water. For appropriate comparison, thesurface sensing area of the microcantilevers is considered. For example, for a rectangular prismatic
microcantilever of dimensions (200×45×12) µm3 and two hammerhead microcantilevers of dimensions[(200×45×12) +(50×200×12)] µm3 and [(150×45×12) +(50×200×12)] µm3, the results show that theresonance frequencies are 1.412 MHz, 0.512 MHz and 0.738 MHz, the percent changes of the resonancefrequency from air to water are 8.8%, 3.8% and 3.0%, the quality factors are 36, 30 and 40 in water, andthe normalized surface mass sensitivities (relative frequency shift/unit mass/unit area) are 14.9 µm2/ng,
16.7 µm2/ng and 16.8 µm2/ng, respectively. For the hammerhead microcantilever with a shorter stem,
the quality factor and normalized surface mass sensitivity are 11% and 13% higher than those of theprismatic microcantilever, respectively, although the resonance frequency is lower. For the range ofdimensions considered, if only the length of the stem or head increases, the resulting resonancefrequency, quality factor and mass sensitivity will decrease. In contrast, if only the width of the head
increases, the resonance frequency and mass sensitivity will decrease and the quality factor will increase
for the shorter heads. Such trends can be used to optimize sensor device geometry and frequency
stability. The increase in the surface sensing area and quality factor are expected to yield higher
sensitivity of detection and improved signal-to-noise ratios in liquid-phase chemical sensing
applications.

IFCS-EFTF4-I2-5

Design of SH-Surface Acoustic Wave Sensors for Detection of
ppb Concentrations of BTEX in Water
Florian Bender1, Rachel Mohler2, Antonio J. Ricco3, Fabien Josse1
1

Dept. of Electr. and Computer Eng., Marquette University, Milwaukee, WI 53201-1881
2
Chevron Energy Technology Co., 100 Chevron Way, Richmond, CA 94801
3
Dept. of Electr. Eng., Center for Integrated Systems, Stanford University, Stanford, CA 94305
email: fabien.josse@mu.edu
An SH-SAW (shear-horizontal surface acoustic wave) sensor system for speciation of BTEX (benzene,
toluene, ethylbenzene, and xylenes) in water is under development. Due to the carcinogenicity ofbenzene, it is necessary to quantify benzene concentrations in the presence of the other aromaticcompounds down to parts per billion (ppb) levels. This is not trivial as benzene has the highest solubility
in water among the BTEX compounds. While the required selectivity can be achieved through the use ofdifferent polymer coatings in a sensor array and evaluation of transient response information, various
strategies are currently under investigation to improve the detection limit for benzene, including new
designs of the SH-SAW sensor platform.
Using suitable multi-electrode IDT (interdigital transducer) designs, a sensor array can be implemented
utilizing identical devices with different coatings and operating at different frequencies, hence achieving
different sensitivities and with different optimal sensing film thicknesses. Fig. 1 shows the spectrum ofan SH-SAW sensor using an Se = 20 transducer design (Se is the number of fingers per electrical period):
for each electrical period, two electrode fingers connected to the positive bus bar alternate with 18
fingers connected to the negative bus bar. A spectrum of well-separated SH-SAW harmonics can beseen, which is useful to obtain a maximum of information in sensor array measurements. It also permits
a more comprehensive characterization of the viscoelastic behavior of polymer films (at various
thicknesses) at different frequencies in a single measurement. Fig. 2 shows initial measurements on thedetection of 5 ppm benzene in water, performed with this sensor design using a 0.55 µm thick poly(ethyl
acrylate) coating. A ratio of the frequency shifts, Δf (164 MHz) / Δf (123 MHz), of 2.80 was found,higher than the ratio of 1.78 expected for pure mass loading where Δf  f2 . This finding indicates more
efficient waveguiding and/or frequency-dependent viscoelastic effects at 164 MHz for this coating. In a
separate experiment, detection of 200 ppb benzene in water was successfully demonstrated for the164MHz harmonic. A detection limit of 20 ppb is also estimated for ethylbenzene.
-15-20

Loss (dB)

-25
-30
-35

-40
-45
-50
-55
0

50

100

150

200

250

300

Frequency (MHz)Fig. 117: Transmission spectrum of an SH-SAW
sensor, coated with 0.3 µm poly(methyl
methacrylate), in air, showing harmonics at
multiples of 41 MHz.

Fig. 2: Response of the SH-SAW sensor, coatedwith 0.55 µm poly(ethyl acrylate), to 5 ppm
benzene (- - 123-MHz mode, — 164-MHz mode).

Integrated MEMS Circuits
CLUB H
Wednesday, July 24 2013, 04:30 pm - 06:00 pm
Chair:

Gianluca Piazza
Carnegie Mellon University

IFCS-EFTF1-I3-1

Wentao Wang1, Radhika Marathe1, Bichoy Bahr1, Laura C. Popa1, Dana Weinstein1
1
MIT, USA

RF Solid-State Vibrating Transistors
Wentao Wang, Radhika Marathe, Bichoy Bahr, Laura C. Popa, Dana WeinsteinMIT, Cambridge, MA, USA
Email: dana@mtl.mit.edu
Semiconductor micro-electromechanical (MEM) resonators, with quality factors (Q) often exceeding
104 can provide a high performance, low-power, compact IC-compatible alternative to electricalcomponents in clocking, communication, and sensing applications. Key challenges to wide-spread
implementation of these devices include complex fabrication, packaging, and frequency scaling. The
work presented here focuses on new transduction mechanisms and new resonant structures that enableintimate integration with ICs at multi-GHz frequencies.
The majority of electromechanical devices require a release step to freely suspend moving structures.
This necessitates costly complex encapsulation methods and back end-of-line processing of large-scale
devices. Instead, we present the development of unreleased Si-based MEMS resonators in CMOS,
allowing seamless integration into Front End of Line (FEOL) processing with no post-processing or
packaging.
To address frequency scaling up to mm-wave frequencies, we introduce the Resonant Body Transistor(RBT) which can be integrated into a standard CMOS process. The unreleased, Si bulk acoustic
resonators are driven capacitively using the thin gate dielectric, and actively sensed using a field-effecttransistor (FET) incorporated into the resonant cavity. FET sensing with the high fT, high performancetransistors in CMOS amplifies the mechanical signal before the presence of parasitics. The resulting RFMEMS resonators can provide low power, low cost, small footprint building blocks for on-chip signal
generation and processing. For low loss and high power applications, this concept can be extended to
III-V semiconductors commonly used for mm-wave ICs (MMICs). We present our latest results on
multi-GHz MEMS-HEMT resonators in GaN and their implications for channel-select radio design.

Fig. 1. Si Resonant Body Transistor
demonstrated in IBM’s 32nm SOI process. The
unreleased resonator is acoustically confinedwith Acoustic Bragg Reflectors formed using
the CMOS stack, and exhibits resonance at 11
GHz.

Fig. 2. AlGaN/GaN Resonant Body Transistor using
HEMT sensing to achieve >3 GHz resonance with thehighest f.Q product in GaN to date. Furthermore,unique properties of AlGaN/GaN enable DC
switching of piezoelectric transduction in theresonator.

IFCS-EFTF1-I3-2

Enhanced Temperature Sensitivity of a Single CMOS-MEMS
Resonator via Resonant Modes in Orthogonal Axes
Ming-Huang Li, Chao-Yu Chen, Cheng-Syun Li, Chi-Hang Chin, and Sheng-Shian Li
Inst. of NanoEngineering and MicroSystems, National Tsing Hua University, Hsinchu, Taiwan
Email: s100035807@m100.nthu.edu.tw
A novel CMOS-MEMS composite ring resonator capable of a dual-mode operation has been proposed
to enable self-temperature sensing in a single device. To maximize the temperature sensitivity between
the dual modes, two resonant modes of a single resonator vibrating in orthogonal axes (i.e., in-plane andout-of-plane) are chosen due to the large difference of their temperature coefficients of frequency (TCf).
The different thermal-frequency behaviors were realized by the flexibility of the structural configurationfrom the CMOS back-end-of-line materials where metals (aluminum and tungsten) provide a negative
TCf while, in contrast, dielectrics (SiO2) offer a positive TCf. By adjusting the constituent ratio and theposition of metals and dielectrics through CAD layouts,
INP Side Electrodes
different TCf’s have been successfully demonstrated in aA’single CMOS-MEMS resonator. From the experimental
results, the measured frequency and temperature response of
the in-plane (INP) resonant mode yields a resonancefrequency of 6.5 MHz, Q of 1100, and TCf of -53 ppm/°C. In
contrast, the out-of-plane (OOP) resonant mode yields aAresonance frequency of 5 MHz, Q of 2300, and TCf of Resonator
79 ppm/°C. As compared to the prior arts361,362, a largest TCf OOP Bottom Electrodes
difference enabled by a single resonator (-26 ppm/°C Fig. 118: Optical view of a CMOSbetween modes) to date is achieved.
MEMS ring resonator, indicating its inA ring-shaped resonator with four nodal supports plane (INP) and out-of-plane (OOP)
surrounded by its INP side electrodes and OOP bottom electrodes.
electrodes is depicted in Fig.1. This device was fabricated ina maskless metal wet-etching 0.35m CMOS-MEMS
platform363. A detailed cross-section view of the resonator isshown in Fig.2a where the dotted arrows indicate the (a)vibrating directions. Since the resonator is a sandwiched
metal-oxide composite, it allows us to design different TCf’s
in different axes. To understand the temperature sensitivityof the dual-mode resonator, the measured thermal responseis shown in Fig.2b. The beat frequency of the dual-mode
resonator2 is defined by fbeat = (fINP/N1)-(fOOP/N2) where N1
and N2 are scaling factors. By properly choosing N1=64 and (b)N2=50, an estimated maximum beat frequency sensitivity Fig. 119: (a) Cross-section view of theof 3760 ppm/°C is obtained by a liner curve fit (R2=0.92), proposed resonator. (b) Measured
temperature responses of the resonator.
as shown in the right Y-axis of Fig.2b.
The estimated beat frequency drift isshown in the right Y-axis.
361

M. Koskenvuori, et al., “Temperature measurement …,” MEMS’08, Tucson, USA, pp. 78-81, 2008.

362

M. J. Dalal, et al., “Simultaneous dual-mode ...,” MEMS’11, Cancun, Maxico, pp. 489-492, 2011.

363

W.-C. Chen, et al., “A fully-differential …,” IEEE Electron Device Lett., vol. 33, no. 5, pp. 721-723, May 2012.

IFCS-EFTF1-I3-3

Stress-enhanced chemical vapor deposited graphene NEMS RF
resonators
Michael Lekas1, Sunwoo Lee1, Changyao Chen2, James Hone2, Kenneth Shepard1
1
2

Department of Electrical Engineering, Columbia University, New York, NY, USA
Department of Mechanical Engineering, Columbia University, New York, NY, USA
Email: msl22@ee.columbia.edu

Graphene has received much attention owing to its exceptional electrical and mechanicalproperties364,365. For electronic applications, graphene has been explored as a channel material for RF
field-effect transistors (FETs)366. In nano-mechanics research, RF mechanical resonators have been
made using graphene to take advantage of its high strength and stiffness, and low mass367.
By operating a graphene nanoelectromechanical resonator (GNER) as a mechanically resonant FET,
both the electrical and mechanical advantages of the material can be combined to improve thetransduction of mechanical resonance368. Vibrations are electrostatically actuated in a suspended
graphene channel by applying an RF signal and DC bias between the channel and an underlying gate.
Displacement of the graphene channel relative to the gate modulates the charge density in the graphene,
which is then sensed as a drain current modulation. This transduction technique has opened thepossibility of using GNERs in RF circuits such as filters and oscillators.
Current obstacles to application of GNERs include process scalability concerns, poor transduction atroom temperature, and low resonance frequencies (fo). In this work we present RF measurements of
GNERs taken at room temperature with Q’s of about 100 at frequencies above 190 MHz, which, to thebest of our knowledge, are the highest values to date for non-cryogenic measurements of GNERs.
Additionally, tuning of fo over morethan 5% bandwidth is demonstrated
through application of a DC gatebias of 5V. Yield and fo are
improved by straining the suspended
graphene using an SU-8 polymer
clamp, and chemical vapor deposited(CVD) graphene is used todemonstrate the scalability of theprocess.
Fig. 120: SEM of GNR with SU-8Fig. 121: Resonance signal (S21)
clamp.
as a function of gate voltage.

364

Novoselov, K. et al, “Electric field effect in atomically thin carbon films,” Science, vol. 306, p.666-669, 2004.

365

Lee, C. et al, “Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene,” Science, vol. 321, p.
385-388, 2008.
366

Meric, I. et al, “Current saturation in zero-bandgap, top-gated graphene field-effect transistors,” Nature Nanotech., 2008.

367

Bunch, J.S. et al, “Electromechanical resonators from graphene sheets,” Science, vol. 315, p. 490-493, 2007.

368

Xu, Y. et al, “Radio frequency electrical transduction of graphene mechanical resonators,” Appl. Phys. Lett., vol. 97,
2010.

IFCS-EFTF1-I3-4

Micromechanical Disk Array-Composite for Enhanced
Frequency Stability Against Bias Voltage Fluctuations
Lingqi Wu1, Mehmet Akgul1, Zeying Ren1, Clark T.-C. Nguyen11Dept. of EECS, University of California at Berkeley, Berkeley, CA, USA
Email: wulingqi@berkeley.edu

A 215-MHz polysilicon capacitive-gap transduced micromechanical resonator array employing 50
mechanically coupled contour mode disks (cf. Fig. 1)—the largest such array yet fabricated andmeasured—has achieved 3.5× better frequency stability than single stand-alone disk counterparts against
fluctuations in the dc voltage (VP) normally dropped across the electrode-to-resonator gaps during
device operation. Here, connection of numerous resonators via half-wavelength (λ/2)-dimensioned
coupling beams produces a single array-composite resonator that selectively resonates at a single mode
frequency with all resonators moving in phase. The key to enhanced frequency stability against bias
voltage variation is the electrode-to-resonator
Electrode to
C0
Resonator
Capacitancecapacitance (Co) generated by the parallel combination of
Input
Electrode
input/output electrodes overlapping each resonator in the
d=50nmRP
RP
array. Co dominates among elements loading theBiasresonator and effectively raises its stiffness (beyond theVoltage(V )stiffness increase resulting from mechanical coupling),much like a varactor does in crystal circuits. This in turn
Disk
OutputRP
reduces the efficacy of the bias voltage-controlled Resonatorλ/2 Coupling Electrode369
electrical stiffness . The more resonators in the array,Beamthe smaller the frequency shift imposed by a given bias
Fig. 122: SEM of a 215-MHz 50nm
voltage change. This result suggests that the most stable capacitive-gap transduced contour mode disk
MEMS-based oscillators (e.g., against supply noise and array employing 50 mechanically coupled
acceleration370) are ones that utilize mechanicallyresonators.
coupled arrays of resonators.
Measurement data

Comment [ctn5]: Somewhere in the figure, youneed to show the dc bias.

Frequency Change [ppm]

P

Array

Simulation(N =50)Fig. 2 presents measured curves of frequency versus bias
Arrayvoltage for the array-composite resonator of Fig. 1, all(N = 16)alongside theoretical curves predicted by an equivalentcircuit modeling the above phenomena for arrays with
Singledifferent numbers of resonators. Here, theory andResonator(N = 1)
measurement match quite well. The 50-element 215Array(N = 8)MHz array experiences a 20ppm frequency change when
VP varies by 9V, which represents a 3.5× improvement
DC-bias Voltage VP [V]over the 70ppm of a single resonator and could
potentially improve the acceleration sensitivity of a Fig. 2: Measured curves of resonancefrequency versus dc-bias voltage VP plotted
MEMS based oscillator by 11dB.

against simulation using equivalent circuit
models for resonator arrays with N=1, N=8,
N=16 and N=50.
369

Frank D. Bannon III, J. R. Clark, and C. T.-C. Nguyen, “High-Q HF Microelectromechanical Filters”, IEEE J. Solid-State
Circuits, vol. 35, no. 4, pp. 512-526, April 2000.
370

T.L. Naing, T. O. Rocheleau, Z. Ren, E. Alon, and C. T.-C. Nguyen, “Vibration-Insensitive 61-MHz Micromechanical
Disk Reference Oscillator”, IEEE Int. Frequency Control Symposium, Baltimore, Maryland, pp. 276-281, May 2012.

Comment [ctn6]: reference Frank Bannon's JSSC
filter paper.

IFCS-EFTF1-I3-5

Exploiting Structural Nonidealities in MoS2 NEMS Resonators forMode Shape Engineering and Frequency Control
Zenghui Wang1*, Jaesung Lee1, and Philip X.-L. Feng1*
1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
Email: zenghui.wang@case.edu, philip.feng@case.edu

Nanoelectromechanical systems (NEMS) made of atomically-thin crystalline nanostructures havedemonstrated attractive potential for new actuators and sensorsxvii,xviii. New types of 2D materials areoften first obtained by mechanical exfoliation which usually leads to imperfect device geometries. In
this work, we study ultrathin molybdenum disulfide (MoS2) NEMS resonators, with focus on
investigating the effects of structural nonidealities and asymmetries on the device characteristics. We
observe that structural nonidealities such as irregularities in shapes, boundaries, thicknesses, andgeometrical asymmetries do not compromise device performances. Instead, they provide an additional
geometrical degree of freedom which allows novel engineering of the device’s mechanical behavior,such as controlling the mode shape and mode index, as well as tuning the frequency ratio between
different resonant modes. This capability is interesting for designing multimode and nonlinear resonant
components in nanomechanical circuits.

S1/2(V/Hz1/2)
V

S1/2(V/Hz1/2)
V

Resonance Frequency (MHz)We fabricate MoS2 NEMS resonators using photolithography, wet etching, and mechanical exfoliation.
For each device, we measure its room-temperature thermomechanical resonance with an ultrasensitive
interferometricsystem,
and
0.35
0.4
characterize the device with
optical microscope, SEM, and
0.30
40
0.2
AFM (Fig. 1 top insets). We
0.25
observe that devices with
15
30
46
48
50
nonideal geometries can haveboth
Frequency (MHz)Frequency (MHz)highfundamental-mode
resonance frequency f (in the20
VHF band) and good quality
factor (Q>300), showing nodegradation from normal devices.
Figure 1 shows results from0
COMSOL
simulations
of
0
90
180
incompletely covered resonators.
Data
Uncovered Portion (degree)in this work reveal very Fig. 1: Effect of incomplete coverage on device resonance for ainteresting effects and rich insight MoS2 diaphragm clamped above a circular microtrench. The three into
the mode shape and frequency lowest modes are shown, with mode shapes illustrated for
scaling. These include: (i) mode different degrees of partial coverage. Top Insets: measured
splitting due to symmetry mechanical resonances, optical images, and SEM images of two
breaking; (ii) robust performance such MoS2 nanomechanical devices. The uncovered portion isinspite of structural irregularities; quantified by its radius angle (SEM images). Scale bars: 2µm.
(iii)
non-monotonic dependence of frequency on the degree of geometric imperfection; (iv) mode crossing in
multimode systems; (v) lifting of degeneracy from broken symmetry.

IFCS-EFTF Group 1 poster session 2
Forum Hall
Wednesday & Thursday, July 24-25, 2013, 1:00 pm - 2:00 pm and 3:30 pm - 4:30 pm
Chair:

Derek Puccio
Quartzdyne

IFCS-EFTF1-PCD1-1

Experimental and theoretical results on SC-cut quartz
resonators collectively realized on 4” wafers
A. Clairet1, T. Laroche2, L. Couteleau1 and J-J. Boy3
1

2

RAKON France, 2 rue Robert Keller, 10150 Pont-Sainte-Marie, FRANCE
FEMTO-ST, Frequency & Time Dept, 26 chemin de l’Epitaphe, 25000 Besançon, FRANCE
3
ENSMM, FEMTO-ST, 26 chemin de l’Epitaphe, 25000 Besançon, FRANCE
Email: alexandre.clairet@rakon.com

In the light of modern computer modeling, innovative processes and a multidisciplinary approach ofresearch and industry, our project (for more details, see also 1) has been proposed to revisit designing
low-cost miniaturized quartz resonators without compromising performance characteristics. The use of
CAD tools has allowed the optimization of quartz resonators.
In order to produce collective SC-cut quartz resonators, we achieved 4” wafers (standard of
microelectronics) in which our prototypes are cut. Each of these resonators are encapsulated undervacuum to not damage their performances and toinsure the best of them, furthermore guaranteed by
selected clamping. In order to ensure these two
requirements, a procedure of wafer bonding(quartz on quartz with SC-cut wafers) is adopted(see Fig. 1). This process is well known in thesilicon industry and has been adapted to quartz
and intended products.
Considering the active part of the resonator andknowing that a structure with radius of curvatureis hardly compatible with collective fabrication,
we have realized plano-plano structure working at
14 MHz on the 3rd overtone of their slowest
thickness
shear
mode,
calledC-mode(corresponding to the thickness of the wafer of Fig. 123: Prototype
about 380 µm). The main task of this project was
to optimize the geometrical and the physical parameters of the prototypes. Thanks to Finite Elements
Method (FEM), we were able to find optimal characteristics such as Motional parameters, Q-factor…
In this paper, first of all, we present the characterization of the wafers (in terms of orientation, roughness…) and then, we describe the manufacturing steps of the prototypes (collective process for micromachining of the entire surface of the quartz …).
Next, the theoretical results are compared to measurements performed on prototypes. We have observed
a good agreement between the experimental results and those obtained with FEM software (COMSOLMultiphysics®).
A. Clairet et al., “Modeling of BVA resonators for collective fabrication”, Proceedings of the European
Frequency and Time Forum, pp. 49-52, Gothenburg, Sweden, April 2012
1

IFCS-EFTF1-PCD1-2

Vector Network Analyzer Measurements of Frequency
Fluctuations in Aluminum Nitride Contour-Mode Resonators
Nicholas Miller, Gianluca Piazza
Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh,
Pennsylvania, USA
Email: njmiller@andrew.cmu.edu
In order to engineer high precision compact MEMS enabled frequency sources it is of fundamental
importance to identify the principle noise mechanisms in the oscillator circuit. These noise sources canbe mainly partitioned into two groups: those originating in the amplifier and those originating in theresonator. In this work we investigate the latter, and, for the first time, we demonstrate the measurementof frequency fluctuations in a 586MHz one-port aluminum nitride contour-mode resonator using avector network analyzer (VNA). We compare the resonator measurement with measurements of aclosed-loop oscillator employing the same resonator and find good agreement, see figure 1.

2

dB rad /HzThe frequency fluctuations of a 1-port resonator create a phase noise in the reflected signal through thephase/frequency slope of the resonator at resonance,[], where Γ is the reflection coefficient.
This factor depends on the resonator’s100
motional inductance and impedance
Resonator measurement
matching relative to the 50Ω VNA. For
Oscilator phase noisef -3.2
50
VNA measurement floor
small high frequency resonators with
only
-2.3
f
a few Ohms of impedance mismatch,
this0number can be very small and rendersany
f -3.2
homodyne measurement particularly-50
challenging. For our resonator, this
thisfactor is. In order to uncoverf -4.9-100
noise it is necessary to employ a
sufficiently low noise homodyne setup
tof -3.0f 0.0
remove the phase noise of the source. A-150
bridge setup is also required if the
-1
1
3
5
7
source frequency noise is greater than
that
10
10
10
10
10
Frequency, Hzof the resonator1, though this was notneeded in our case. In order to achieve Figure 1: Open-loop measurement of resonatorsufficiently low measurement noise, the frequency fluctuations, referred to closed-loopIFfrequency bandwidth of the VNA must phase noise by dividing by , compared with thebesufficiently low and sets the upper phase noise of a closed-loop oscillator employing
bound of the spectral offset frequency the same resonator. The open-loop measurement isthatshown to be well above the VNA measurement
can be measured.
floor. The noise exponents were fit with least
1
E. Rubiola et al. “Flicker Noise Measurementofsquares.
HF Quartz Resonators”, IEEE Trans. on
Ultrason., Ferroelectr., Freq. Control, vol. 47, no. 2, 2000.

IFCS-EFTF1-PCD1-3

New Calibration Method for Experimental Study of the Nonlinear
Behavior of a Bulk Acoustic Wave Resonator Subject to a HighPower Signal
Catherinot Lise1, Bila Stéphane2, Chatras Matthieu2, Cros Dominique2
1

Innovation Department, TRONICO, Nantes, France
XLIM -UMR n°7252- Université de Limoges/CNRS, Limoges, France
Mail: lcatherinot@tronico-alcen.com
This paper deals with experimental studies of nonlinear behavior of Bulk Acoustic Wave (BAW)
devices, in a Solidly Mounted Resonator (SMR) structure. The purpose is to extend the Modified
Butterworth Van Dyke model to a complete non-linear model of a BAW resonator, which takes into
account all nonlinear effects. Frequency shifts were studied when high Radio Frequency (RF) power (upto 5W) is applied to the resonators. We have focused on the W-CDMA frequency standards, forresonators of emission filters of a front-end module in mobile phones. To stabilize the input power, wehave developed a new calibration method, which is able to match the data correction between a high andsmall signal at any frequency. With this method, we have access to the power waves, and we recalculate
the S-parameters externally as a function of the frequency sweep.
2

A 4-port Vectorial Network Analyzer (VNA) is used both as a measuring device and an RF source. It
delivers -20dBm power, swept around 2GHz. The signal is amplified by a Power Amplifier (PA) (40dBgain) previously characterized as sufficiently linear for the frequency range used. All used devices forthe test bench, including attenuators and couplers, have been chosen to be functional in the frequency
band. Finally, the test bench is connected to a probe station to overcome various effects such as
landslides, claw arks on the wafer or apparatus damage. In addition, the set up has a power sensor
connected to the resonator’s input, in order to monitor the input power, which enables a power feedback
loop. This is a particularly delicate step that requires the establishment of an original procedure of
double calibration (frequency/power). This calibration method simplifies the equipment and locates the
input power measurement very close to the resonator. Initially, a calibration is performed on the power
level output of the coupler, so that the VNA corrects the power supplied simultaneously: the power iswell known in the DUT plane and it is fixed, and we also take into account the losses in the probe
cables. In a second step, a standard S-parameters calibration is carried out under the probes (Short Open
Load Thru), so low power and high power are enabled. The choice of the maximum power value wasstudied taking into account return wave limits of the measuring devices and power densities permitted
on the resonators that are being evaluated for future use as the input stage of mobile phones emission
filters.
We performed measurements on small resonators (100*100µm2 and 50*50µm2), with rectangular andapodized shape. The maximum input power value is 34 dBm, above which we observe device breakage(deterioration of the top electrode, undesirable resistive effects on the access pads). The power density
varies between 36dB/mm2 and 60dB/mm2. In particular, a frequency shift is observed on the resonant
frequency, which decreases by 5% from its initial value from 20 dBm to 34 dBm. Contrary to what was
expected, the anti-resonant frequency, which is directly related to the electric C0 capacitance value, does
not vary. To conclude, the observation leads to consider the couple Lm/Cm, of the motional branch of the
MBVD model, as nonlinear lumped components. Evolution of the test bench is being considered,specifically to further knowledge on mechanical and spectral aspects.

IFCS-EFTF1-PCD1-4

Numerical Study of the Impact of Process Variations on the
Motional Resistance of Weakly Coupled MEMS Resonators
Andreja Erbes, Pradyumna Thiruvenkatanathan, Ashwin A. Seshia
Engineering Department, University of Cambridge, Cambridge, United Kingdom
Email: ae279@cam.ac.uk
Although one-dimensional mechanical coupling (1D-κ) has been suggested as a potential route to reducethe motional resistance (Rx) of electrostatically transduced MEMS resonators371, variations induced bymanufacturing tolerances in weakly coupled systems often result in non-uniform reductions in the Rx
from the case of perfect symmetry372. In an attempt to obtain a better scalability and more predictable Rx
reduction of such weakly coupled arrays, this paper presents a numerical study of the robustness of theachievable Rx to process induced variations for three classes of mechanical coupling topologies: 1D-κ(Fig. 1a), cyclic-coupling (C-κ, Fig. 1b) and cross-coupling (X-κ, Fig. 1c). The numerical study is basedon a flexural mode Si MEMS double-ended-tuning fork (DETF) resonator operating at 270 kHz (Fig.
1a) where the normalized inter-resonator spring coupling is κ = kc/k = 5x10-3. Monte Carlo numericalsimulations, which accounted for up to ± 1.35% random variations in resonator beam widths (nominal
value of 6 μm), were initiated to produce Rx estimates of the three coupling schemes for N = 1, 2, 3, 4, 5
and 9 resonators. The Rx distribution for the special case of N = 4 and N = 9 is shown in Fig.2 where aclear decrease in the spread and mean value of Rx is seen as we switch towards the X-κ topology. The
results for the other array lengths N are summarized in Table 1 where the mean (μ) and standard
deviation (σ) of the Rx distribution for the different coupling schemes are reported. The numerical trends
suggest an improvement in the mean and spread of Rx as N is increased for the X-κ scheme. Thesenumerical results motivate in-depth studies of alternative coupling topologies, in the case of weakly
coupled resonators, towards designing process tolerant, highly scalable resonator arrays.

Fig. 1: Discrete element model N = 4 a) 1D-κ andoptical micrograph of the equivalent coupled DETF
MEMS device; b) C-κ; c) X-κ scheme.
N
Scheme

1D-κ
C-κ
X-κ

1

2

Fig. 2: Normalized Rx distribution when a) N = 4; b) N = 9
for 1D-κ, C-κ and X-κ schemes.
Table 13
4
5
9

μ (kΩ)σ (kΩ)μ (kΩ)σ (kΩ)μ (kΩ)σ (kΩ)μ (kΩ)σ (kΩ)μ (kΩ)σ (kΩ)μ (kΩ)σ (kΩ)

140

1.05

92.0

13.4

77.2
63.1

18.5
10.63

71.6
56.1
46.5

20.8
13.1
7.8

69.13
53.9
35.8

22.0
14.8
5.14

66.5
54.7
17.8

22.4
17.1
0.99

371

Demirci, M.U.; Abdelmoneum, M.A.; Nguyen, C.T.-C.; , "Mechanically corner-coupled square microresonator array for
reduced series motional resistance," TRANSDUCERS, Solid-State Sensors, Actuators and Microsystems, 12th International
Conference on, pp. 955- 958 vol.2, 2003.
372

Erbes, A.; Thiruvenkatanathan, P.; Seshia, A.A.;, "Impact of mode localization on the motional resistance of coupled
MEMS resonators," in Proc. 2012 IEEE Int. Freq. Control Symp., 2012, pp. 609-614.

IFCS-EFTF1-PCD1-5

Unwanted Transverse Modes in SAW Resonators Caused by Stitching
Errors And Stripe Nonlinearities
Pierre Dufilie, Raymond Zeitler, Merle Yoder
Phonon Corporation, Simsbury, CT, USA
Email: pierred@phonon.com

High Q SAW and STW resonators utilize interdigital transducers with transverse weighting. This weighting is fit to thefundamental mode (S0) of the resonator cavity, so the transducer should not couple to the higher order transverse modes (S1,S2, ...). Errors in the actual resonator pattern caused by stitching errors in laser generated photomasks will introduce anasymmetry which can excite both higher order symmetric (S2, S4, ...) and antisymmetric (S1, S3, ...) transverse modes. Nonuniformities due to processing can also contribute to these higher order modes. Higher order modes in oscillators are
undesirable because they degrade linearity or induce frequency popping.
The majority of high resolution (0.5um or better) 1X photomasks are fabricated using laser mask-making machines. Thisapproach is adequate for most SAW devices; however SAW resonators are very sensitive to small variations in linewidths
and line positions -- variations that cannot be detected by normal optical examination. A typical resonator pattern is too large
to be exposed in a single laser stripe (2mm x 2mm active area).
The objective of this study is to determine the photomask fabrication method which can minimize the higher order transverse
modes. A 695MHz STW resonator was designed and realized in an array of 26 rows and 16 columns on multiple 1x dark
field quartz masks exposed with different photomask tools. The tools were Etec Alta 3500 and 3900 laser pattern generators,
Micronic laser writer and an ASET 645 15" Image Repeater used with a 10x reticle.
Multiple wafers were contact-printed from each mask, and all dies on the wafers were RF-probed to acquire S11 over aspan of 40MHz centered at 695MHz. The data was converted to admittance, and the main response was fitted to a lumpedelement model, which was then removed. The residual data, which contained the extraneous modes, was then analyzed forcorrelation to: position in the array of dies; mask technology; wafer number.
Electrical measurements of SAW resonators fabricated with different photomask tools do exhibit differences in transverse
mode levels, the newer pattern generators having the lower high order modes. Those fabricated with mask generated with the
10X stepper exhibited the best performances.

IFCS-EFTF1-PCD1-6

Imaging surface acoustic waves propagating on ST-quartz using stroboscopic
synchrotron radiation X-ray topography.
B. Capelle, A. Soyer, Y. Epelboin, J. Detaint.
Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), UMR 7590 CNRS. Université
Pierre et Marie Curie et CNRS. 4, place Jussieu 75005 Paris. France.
Email: Bernard.Capelle@impmc.upmc.fr
This method allows obtaining instantaneous images of the acoustic wave propagating on crystal
if the frequency of the wave is an exact integer multiple of that of the very short x-ray pulses deliveredby the synchrotron [1]. Depending on the diffraction set–up it is often possible to image separately thedifferent components of the displacement (or more precisely of several of their spatial derivatives,proportional to them). Last year, we have shown that the observation technique using section images
allows getting information about the distribution of the amplitude in the depth direction. This was done
for the normal component of the Rayleigh waves propagating on YZ lithium niobate (LNB) withexperiments using the Bragg setting and in comparing the experimental images with simulated ones. The
properties of this material (X-ray absorption and crystal perfection [2]) do not allow good imaging
conditions for the other component of the mechanical displacement (directed along the propagation
direction).
The surface waves propagating on ST-quartz in the x direction present three components ofdisplacement that can be observed practically separately due to the existence of lattice planes whose
diffraction vectors are very nearly or exactly in the direction of these components. Experiments using ST
quartz delay lines operating at 9.507, 11.361 12.781 and 22.722 MHZ were conducted, using different
diffraction conditions, mostly with the BM05 beam line of the ESRF. Translation and section
stroboscopic topographs in Laue or Bragg geometry were obtained using principally the ( 21.0 ), ( 01.1 )and ( 0 1 .1 ) reflections. As expected from the much lower coupling coefficient, the contrasts given by
the progressive SAW are weaker for ST quartz than for YZ LNB, at equal excitation voltage, but they
are fully discernable. As expected, also, the in-plane component perpendicular to the propagation
direction is the smallest one. In the reflection topographs, the static strains due to the metallic films usedin the transducer, produce noticeable contrasts so that the observations of SAW have to be made outsideof it. The section topographs (reflection setting), contain intense contrasts, that are different of thoseobtained for lithium niobate. These contrasts contain also information about the decrease of the normal
displacement in the depth direction (their positions in the image indicate that they were generated atvarious depths in the substrate). The translation and section topographs obtained in the Laue geometry
with practically or exactly in plane diffraction vectors display periodic contrasts. The translation
topographs contain mostly information about the in-plane distribution of the SAW amplitude close to thesurface. The section images contain a particular distribution of contrast in the depth direction; they giveso, in an indirect manner, information about the variations of the amplitude of a component with thedepth. To better understand these features and the information contained in the various kinds of
topographs, simulated images are being computed in solving numerically the Takagi-Taupin partial
derivative equations governing the diffraction process in the crystal deformed by the theoretical surface
waves (or by waves with different spatial variations). They will be compared between them and with theexperimental ones. It is suspected that in few experimental cases, using not very thick substrates andlong wave length (9,507 MHz), another kind of wave not decreasing as the theoretical SAW may be
propagating in the plate.

IFCS-EFTF1-PCD1-7

X-ray imaging of the surface acoustic wave propagation in
La3Ga5SiO14 crystal
Dmitrii Roshchupkin1, Luc Ortega2, Anatolii Snigirev3, Iraida Snigireva3
1

Institute of Microelectronics Technology and High-Purity Materials Russian Academy of Sciences,
Chernogolovka, Russia
2
Laboratoire de Physique des Solides, Univ. Paris-Sud, CNRS, Orsay, France
3
ESRF, Grenoble, France
Email: rochtch@iptm.ru

Progress in modern telecommunication systems and sensors based on SAW-devices urges thedevelopment of methods to study the SAW propagation in solids. Most interesting and promising
methods for the analyses of acoustic wave field in solids are scanning electron microscopy and X-ray
diffraction and topography. Scanning electron microscopy in the mode of the low-energy
secondary electron registration permits the visualization of surface and bulk, traveling and standing
acoustic waves and makes it possible to study diffraction phenomena in acoustic beams and interactionof acoustic waves with crystal structure defects373. X-ray diffraction and topography are the methods ofquantitative analysis and permit studying the acoustic wave fields both in piezoelectric and nonpiezoelectric materials2.
The aim of this work is to study the SAW propagationin the La3Ga5SiO14 crystal by X-ray topography on asynchrotron radiation source.
The possibility of direct imaging of an acoustic wave
filed on the crystal surface was demonstrated on an
acoustically modulated LGS crystal in the saggital
geometry of X-ray diffraction (fig. 1). It is shown thatthe formation of an acoustic wave field image isconnected with the Talbot effect that can be realized
on a synchrotron radiation source under the conditionsof a partially coherent X-ray radiation and strongly
periodic modulation of the crystal lattice with asurface acoustic wave. It was shown that Talbot effectis an ideal instrument for direct imaging of acoustic
wave fields and investigation of acoustic wave
interaction with the crystal structure defects.
Fig. 124: X-ray topograph of the Y  cut of an LGS
crystal excited by SAW.   1 Å;   10 µm;
f 0  234 MHz; reflection (100);  B  4.175 .

373

D.V. Roshchupkin, M. Brunel, “Scanning electron microscopy observation of surface acoustic wave propagation in the
LiNbO3 crystals with regular domain structures”. IEEE Transaction on Ultrasonics, Ferroelectrics, and Frequency Control,
vol. 41, pp. 512-517, 1994.
2
V. Roshchupkin, E. D. Roshchupkina, D. V. Irzhak, “X-Ray topography analysis of acoustic wave fields in the SAWresonators structures”, IEEE Transaction on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 52, pp. 2081-2087,
2005.

IFCS-EFTF1-PCD1-8

Investigation of surface and pseudo-surface acoustic waves
excitation and propagation in La3Ga5SiO14, La3Ga5.5Ta0.5O14, andCa3TaGa3Si2O14 crystals
Dmitrii Roshchupkin1, Dmitrii Irzhak1, Olga Ploticyna1, Evgeny Emelin1, Luc Ortega2,
Sergey Sakharov3, Oleg Buzanov3
1

Institute of Microelectronics Technology and High-Purity Materials Russian Academy of Sciences,
Chernogolovka, Russia
2
Laboratoire de Physique des Solides, Univ. Paris-Sud, CNRS, Orsay, France
3
FOMOS Materials, Mosscow, Russia
Email: rochtch@iptm.ru

X-ray diffraction on acoustically modulated ordering (Ca3TaGa3Si2O14: CTGS) and non-ordering(La3Ga5SiO14: LGS; La3Ga5.5Ta0.5O14: LGT) crystals of langasite family was used to study the processof surface (SAW) and pseudo-surface acoustic waves (PSAW) excitation and propagation374. The
process of the SAW and PSAW propagation in
CTGS, LGS, and LGT crystals can becharacterized by the difference in the directions of
the acoustic energy propagation (PFV) andacoustic wave-vectors.
SAW and PSAW are excited by the sameinterdigital transducer (IDT) but at different
resonance excitation frequencies. Propagation of
SAW and PSAW causes the sinusoidal
modulation of a crystal lattice and appearance ofdiffraction satellites on the rocking curve, with
their number, angular positions, and intensities
depending on acoustic wavelength and amplitude.
The distribution of the diffracted X-ray intensity
on the crystal surface was used for mapping of Fig. 125: Map of acoustic wave field distribution of
SAW and PSAW propagation in CTGS, LGS, and SAW on the Z  cut surface of LGT. E  11 keV;
LGT crystals.
reflection (001);  B  6.595 ;   8 µm. Dark
It was shown that SAW and PSAW are excited by contrast corresponds to the SAW propagation.
the same IDT with the same wavelength, but atdifferent frequencies with different velocities. Also it was measured that SAW and PSAW have thedifferent power flow angles. Fig. 1 shows the difference between the PFV and SAW wave-vector in Z 
cut of LGT crystal (   8 ) at the SAW propagation along Y  30 -direction. Furthermore it was
shown that PSAW is a flow wave, which propagates inside the crystal and can be observed only near
IDT.

374

D. V. Roshchupkin, A. I. Erko, L. Ortega, D. V. Irzhak, “X-ray diffraction analysis of the surface acoustic wave
propagation in langatate crystal”, Applied Physics A, vol. 94, pp. 477-484, 2009.

IFCS-EFTF1-PCD1-9

Investigation of optimal electrode structureof SC-cut resonators
Lepetaev Alexandr, Kosykh Anatoly
Omsk state technical university, Omsk, Russian Federation
Email: LAN@inbox.ru
High-Q SC – cut resonators widely used in precision OCXOs. They have many advantages: higher
compared with the AT-cut value of the frequency factor, high Q, small temperature – dynamic
frequency coefficient. However, these resonators have one disadvantage: the high activity of B – mode
(thermosensitive mode), comparable with the activity of the main C – mode, making it difficult to use insome cases. This is due to the fact that the traditional design of electrodes for double rotated cut
resonators is not optimal. In this paper we consider the optimal design of the electrode SC – cutresonators. It reduces the resistance of the mode C (Rc) and increases resistance to mode B (Rb),
allowing you to get the ratio of Rb / Rc > 5.
Earlier375 we consider the formulas to determine the surface density of the polarization charges atresonator plate surface of arbitrary cut (including SC - cut). This allows you to correctly determine theresistance of a given excitation mode in case of an off-center location of the electrodes, using
information on the distribution of the vibration amplitude by the technique described at article2.
In this paper the results of calculations of the surface charge density carried out for SC – cut resonatorsfor different values of the design parameters (contour radius, thickness, harmonic number). The
electrodes on each side were dividing on two segments, which are connected to different ports of theresonator. The shapes of the electrode segments were changed to obtain high ratio of resistances Rb/Rc.
All calculations were performed using the finite element analysis software FlexPDE and Comsol
Multiphysics.
These constructions are more complex than traditional, but provide the best parameters and stable
excitation of the fundamental mode.

375

Lepetaev A.N., Kosykh A.V. New method of multy-mode oscillations control in crystal resonators. 2012 IEEE
International Frequency Control Symposium Proceedings. Baltimore, MD, USA. May 21-24, 2012, P. 146 – 149.
2
Lepetaev A., Kosykh A., Khomenko I. Numerically-analytical calculation method for vibration amplitude distributions ofinharmonic modes of double rotated cuts thickness-shear resonators. / Proc. of 2007 IEEE Ultrasonics Symposium: New
York, USA, 2007. P. 1393 -1396.

IFCS-EFTF1-PCD1-10

Correction Factors for the Mindlin Plate Equations for Thickness
Vibrations of Crystal Plates with Thicker Electrodes
Dejin Huang, Guijia Chen, Wenjun Wang, Tingfeng Ma, Jianke Du, Ji Wang
Piezoelectric Device Laboratory, School of Mechanical Engineering and Mechanics,
Ningbo University, 818 Fenghua Road, Ningbo, Zhejiang 315211, CHINA
E-mail: wangji@nbu.edu.cn
The Mindlin plate theory has been widely used for the study of high frequency vibrations of quartz
crystal plates for resonator design and analysis. To improve the accuracy, the plate equations have to becorrected for the exact thickness-shear frequencies which in turn ensure the accurate results for othercoupled modes. The correction procedure was suggested by Mindlin and the correction factors for the
first-order equations have been available. Lately, a systematic procedure for the correction factors up to
the fifth-order has been established and two correction schemes with different correction factors havebeen adopted for the higher-order vibrations376. These results have expanded applications of the
Mindlin plate equations to the overtone vibration analysis which is required for the overtone resonators.
One critical issue concerning the applications of the Mindlin plate with correction factors are the effectof electrodes, which are essential part of resonators and complications are resulted. Furthermore, crystal
blanks in resonators are shrinking in the thickness while the electrodes remaining constant, showing therelative increasing of influence of electrodes on the performance of resonators. As a result, further
studies with the consideration of electrodes have been performed for effects on the vibration equations
and solutions377. With this objective in mind, we start from the Mindlin plate equations with a full set ofvibration modes for the consideration of electrode mass and stiffness effects as a continuation of ourearlier studies which only considered the mass effect in terms of mass ratios. The analysis regarding to
the AT-cut of quartz crystal plates show that the consideration of electrode stiffness and mass willchange the correction factors, thus making the equations more accurate in the calculation of frequency
spectra and mode shapes. For very thin electrodes, the correction factors should be the same assuggested by earlier studies. The same procedure is implemented to the SC-cut quartz crystal plates
which have more enhanced couplings of vibration modes due to the material anisotropy. Correction
factors for both AT- and SC-cut quartz crystal plates with consideration of electrode stiffness are given
in polynomials of mass ratios for different metals. We expect the relatively adequate consideration ofelectrodes will provide more effective basis for vibrations of quartz crystal resonators with the truncatedequations for analytical solutions based on the straight-crested wave assumptions and the finite element
implementation of the higher-order equations with a full set of variables.

376

J. Wang, J.-D. Yu, and Y.-K. Yong, “On the correction of the higher-order Mindlin plate theory,” Intl. J. of Applied
Electromagnetics and Mechanics, 22, 83-96, 2005.
377

Jianke Du, Guijia Chen, Wenjun Wang, Rongxing Wu, Tingfeng Ma, and Ji Wang, “Correction Factors of the Mindlin
Plate Equations with the Consideration of Electrodes,” IEEE TUFFC, 59(10):2352-2358, 2012.

IFCS-EFTF1-PCD1-11

Optimizing UHF Quartz MEMs Resonators for High Thermal
Stability
D.J. Kirby, Y.K. Yong*, R.L. Kubena, R. Perahia, D.T. Chang, H. Nguyen, F.P. Stratton, R.J. Joyce,
H.P. Moyer R.G. Nagele & P.D. Brewer
HRL Laboratories, Malibu California, USA, *Rutgers University, Piscataway, New Jersey, USA
Email: djkirby@hrl.com

abs(f/f) (ppm)

Frequency stability of oscillators used in timing applications is of paramount importance. It is wellknown that one dominant source of frequency instability in quartz oscillators relates to the mounting
stresses incurred during wafer bonding1. A resonator bonded to a substrate at elevated temperature andsubsequently cooled can experience significant residual stress in the device active region. As theoperating temperature of the device varies, so does the magnitude of the residual stress. This stress acts
to perturb the device resonant frequency thereby compromising frequency stability. As the need forhigher frequency and smaller devices has developed for many new commercial applications, theseeffects are exacerbated in smaller packages. This paper discusses how ~ 1 GHz ultra-high-frequency(UHF) MEMs thickness-shear quartz resonator designs2 can be optimized for improving thermalfrequency stability via reduced residual stresses.
A newly developed 3-D FEA simulation technique which includes mounting stresses3 is applied to
optimize UHF device designs for high thermal stability. One of the effects of stress is to produce af/f vs. Stress @ electrodes
rotation of the frequency-temperature (f-T)
45
characteristic. Very small stresses can produce
40significant frequency shifts, especially for
35
fundamental mode UHF devices. This rotation30
can often mask the true quartz f-T characteristic25
and results in resonator thermal instability. As
20
an example, Figure 1 shows a simulation of15
frequency perturbation versus stress in the10
active region for a 770 MHz 2-m-thick AT5
cut quartz resonator. The insert of Figure 1
0shows a simulation of the thermally induced-5
stress for a T = +75C of a single-thickness
4
5
6
7
10
10
10
10
quartz resonator rigidly bonded to a siliconStress (Pa)substrate with zero stress at 25o C. A mounting
stress of 130 MPa near the mounts produces a Figure 1. Frequency perturbation of a 2-m-thick 770stress of 1 MPa in the active region and a MHz AT-cut resonator versus stress in the active region.
resulting resonator frequency shift of 21 ppm.
We determine a sensitivity of 1 ppm/50 kPa stress in the active region which represents a significantly
higher frequency sensitivity than for larger and thicker designs. In this paper, simulation results will becompared with experimental data and new UHF resonator designs will be explored for mitigating thiseffect in sub-mm-size UHF quartz resonators.
1

John R.Vig, “Quartz Crystal Resonators and Oscillators for Frequency Control and Timing Applications - A Tutorial",
Rev.8.5.4.4, April 2012.
2"D. Chang et al, “Nonlinear UHF Quartz MEMs Oscillator with Phase Noise Reduction”, Proceedings of IEEE MEMS
2013, Taipei, Taiwan, January 20 – 24, pp. 781, 2013.
3
Yook-Kong Yong et al, "Modeling Approach to Analyze Bonding Stress in UHF Quartz Resonators”., IEEE FCS 2013,
Prague, Czech Republic, submitted abstract.

IFCS-EFTF1-PCD1-12

Modeling Approach to Analyze Bonding Stress in UHF Quartz Resonators
Yook-Kong Yong1, Randall Kubena2, Deborah Kirby2, Raviv Perahia2, and David Chang2
1

Rutgers University, Piscataway, New Jersey, USA, 2HRL Laboratories, Malibu California, USA
Bonding and mounting stress in quartz resonators is known to produce frequency shifts which can also
modify the frequency-versus-temperature (f-T) profiles.1 This stress/strain is produced by two events.
First, when the quartz plate is initially bonded into the final package, the bonding process may require
high temperature annealing or processing. When the package is cooled, the difference in thermal
expansion coefficients between the quartz and the package produces stress that can partially relax toyield an initial stress condition at room temperature. Second, when the package is then varied overtemperature during use, this initial stress is modified by the same thermal expansion coefficientdifferences. Depending on the thermal history of the device, the mounting stress can be minimized or
reduced to zero at a particular temperature (Tref2) as evidenced by a very low relaxation or aging rate.
Previous numerical models for quartz f-T profiles2 have not included this zero stress condition nor thevariations in the stress and strain in the quartz due to the mounts in calculating the f-T profiles. In thispaper, we describe a method within a COMSOL finite element analysis to include these effects for the
first time.
Figure 1. below shows the four states of the resonator and its respective material displacement vectors
U(a), U(b), U(c), and U(d). The small piezoelectric vibrations of the resonator are superposed upon thematerial displacement U(c). We derived the governing equations for small piezoelectric vibrations
superposed on displacement U(c) and employed the derived equations in a COMSOL finite element
model. The displacement U(c) includes both thermal stress and thermal strain but our governing
equations neglect the thermal stress as they are second order effects compared to the thermal strains. The
f-T effect is calculated by the change in eigenfrequency of the thickness shear mode as a function of thetemperature. Compared to soft mounts such as rubber or epoxy, hard mounts can create larger rotationsof the f-T profiles. Our general analysis can be applied to any resonator geometry and mounting design
to optimize the predictability of the f-T profiles and minimize hysteresis and aging. This is particularly
important for UHF shear-mode device designs where micron-thick quartz plates are utilized. Examplesof this effect will be described and presented.

Figure 1: Four states of the resonator and its displacement of material points U(a), U(b), U(c), and U(d), respectively.
1"Quartz Crystal Resonators and Oscillators For Frequency Control and Timing Applications - A Tutorial", April 2012, John
R.Vig.
2"Effects of Thermal Stresses on the Frequency-Temperature Behavior of Piezoelectric Resonators", Y-K
Yong, M. Patel, M. Tanaka, Journal of Thermal Stresses, Vol. 30, No. 6, June 2007, pp. 639 -661.

IFCS-EFTF Group 2 poster session 2
Forum Hall
Wednesday & Thursday, July 24-25, 2013, 1:00 pm - 2:00 pm and 3:30 pm - 4:30 pm
Chair:

Fabrice STHALFEMTO-ST

IFCS-EFTF2-PCD2-1

Dynamic Range Vs Spectral Clarity Trade-off in All-Digital
Frequency Synthesis via Single-Bit Sinewave Quantization
Paul P. Sotiriadis1, Natalia Miliou1
1

Department of ECE, National Technical University of Athens, Greece
Email: miliou@ieee.org

PSD (dB)

Single-bit Nyquist-rate dithered quantization has been proposed for all-digital frequency synthesis andRF signal generation378. This work demonstrates how we can improve the Dynamic Range (DR) beyond
that achieved using independent and uniformly distributed dithering sequences by selectively allowing
some of the harmonics to be present in the spectrum; here DR is the ratio of the carrier’s power tonoise’s power spectral density. For a dithered
single-bit
quantized
sinewave,0
DR = 89.5 dB-10x k  sgn  cos  k   uk  , where u k is the dithering,f = 1 GHzs

-20

RBW = 3125 Hz
we express the Cumulative Distribution Function-30
Nav = 10
(CDF) of u k using Chebyshev polynomials, i.e.
-40
-50
1 1 
-60
where
are
G  u     j 0  jT j  u  ,
aj
0
0.2
0.4
0.6
0.8
1
f / fs2 2rdappropriately chosen. Allowing the 3 harmonic Fig 126: Normalized PSD when a1  9 / 8 , a3  1/ 8
 3 mod 2  /  2 Ts  to be present is equivalent to and all other coefficients k  0 ; w  25 , q  64

having 1 , 3  0 and all other coefficients k  0 .
a1   6  3  / 8

  0,1 .



a1 , a3

a3   2  3  / 8

and

is
with

It

is



DR  10log10 a /  2  a  a   10log10  f s   3.01,
2
1

2
1

2
3

0

DR = 91.3 dB

3rd

-10
PSD (dB)In this case the feasible set of

5th

-20

fs = 1 GHz
RBW = 3125 Hz
Nav = 10

-30
-40
-50
-60
0

0.2

0.4

f / fs

0.6

0.8

1

when q  4 , and DR is maximized for a1  9 / 8 and Fig 127: Normalized PSD for a1  1.191 , a3  0.237 ,a5  0.047 and all other coefficients zero.

a3  1 / 8 as shown in Fig. 1 ( 89.5 dB forf s  1 GHz ). Allowing both the 3rd harmonic andthe 5th one,  5 mod 2  /  2 Ts  , means that 1 , 3 , 5  0 and all other coefficients  k are zero. The
feasible set of a1 , a3 , a5 is the union of a triangle and an ellipse, including their interior points, in theplane of 3 , 5 . It is DR  10 log10 a12 / 2 a12  a23  a52   10 log10 fs   3.01, when q  6 , and DR is
maximized for a1  1.1906 , a3  0.2375 , a5  0.0469 as shown in Fig. 2 ( 91.3 dB for f s  1 GHz )giving a 4.3 dB improvement with respect to uniformly distributed dither. In some sense part of noise’s
power is absorbed by the harmonics improving DR. The paper provides a methodology for optimizing
the DR along with guidelines for selecting those harmonics located away of the carrier.

378

P.P. Sotiriadis, N. Miliou, “All-Digital Frequency Synthesis based on Single-Bit Nyquist-Rate Sinewave Quantization
with IID Random Dithering”, subm. to IFCS 2013.

IFCS-EFTF2-PCD2-2

Measuring an optical frequency difference of semiconductor
lasers based on coherent detection and frequency dividers
Ł. Buczek1
1

AGH University of Science and Technology, Mickiewicza 30, 30-057 Krakow, Poland
Email: lbuczek@agh.edu.pl

Currently a number of electronic components capable of processing multi-GHz electrical signals isavailable on the market. This allows building a system for measuring the difference of optical carrier
frequencies of two semiconductor lasers, exploiting high-speed frequency prescalers and based oncoherent detection.
The idea of proposed method ispresented in Fig. 1. Two opticalsignals from distributed feedback(DFB) semiconductor lasers aresuppliedtoahigh-speed
photodiode and resulting beatnote
with the frequency equal to thedifference of the laser carriers isfurther processed by a set of highspeed prescalers. They divide thehigh-speed signal to the value low
enough for counting by the system
based on a field programmable
gate
array
(FPGA)
andmicrocontroller. The prototype
system was designed to operatewith the frequencies up to 18 GHz
that corresponds to the wavelength
difference of the lasers up to
0.14 nm. Using currently available
technology this difference may beeasily extended to 26 GHz (i.e.
0.2 nm).

Fig. 1: An idea of measuring the difference of semiconductor lasers
carrier frequencies using high-speed prescalers.

An example of 10-day record
showing the relative stability of
two telecommunication-grade DFB
Fig. 2 The record of 10-days measurement of frequency differenceof two DFB lasers stabilized using Fabry-Perot etalons.
lasers stabilized using Fabry-Perot
etalons is presented in Fig. 2.
Presented method may be used for calibration of time transfer in fiber optic system exploiting two
closely spaced lasers379 or for characterizing ultra-dense WDM laser sources.

379

P. Krehlik, Ł. Śliwczyński, Ł. Buczek and M. Lipiński, “Fiber optic joint time and frequency transfer with active
stabilization of the propagation delay”, IEEE Trans. Instrum. Meas. 61, 2844–2851, 2012.

IFCS-EFTF2-PCD2-3

A 15 mW, 4.6 GHz frequency synthesizer ASIC
with -84 dBc/Hz at 2 kHz for miniature CPT clocks
Yazhou Zhao1, Steve Tanner1, Luc Schneller2, Florian Gruet2, Christoph Affolderbach2,
Gaetano Mileti2, Pierre-André Farine1
1
2

ESPLAB, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
Laboratoire Temps-Fréquence (LTF), University of Neuchâtel, Neuchâtel, Switzerland
Email: yazhou.zhao@epfl.ch, pierre-andre.farine@epfl.ch

We report on the development and evaluation of a 4.6 GHz frequency synthesizer CMOS ASIC for
miniature atomic clocks based on Coherent Population Trapping (CPT) in micro-fabricated Cs vapor
cells. The circuit consumes 15 mW and features a frequency resolution below 10-13.
For guaranteeing the lowest power consumption and the smallest form factor for miniature atomic
clocks, an application specific integrated circuit (ASIC) is the best choice compared to commerciallyavailable synthesizers. Here we report on an improved circuit compared to a previous design380. It
includes an LC Voltage-Controlled Oscillator (VCO) and a fractional PLL with a reference frequency of
20 MHz and a bandwidth of 200 kHz. The 40-bit fractional divider allows sub-mHz frequency
resolution at the 4.6 GHz output. The VCO controls a high-efficiency Power Amplifier (PA) with
programmable differential output power from -10 to 0 dBm in 64 steps. The circuit is fabricated into a
130 nm CMOS process, is powered at 1.2 Volt.
The circuit was characterized with a 20 MHz reference OCXO featuring a phase noise of –87 dBc/Hz at
1 kHz from carrier (referred to a 4.6 GHz carrier). The ASIC phase noise was measured at –82 dBc/Hz
at 1kHz and ≤ –84 dBc/Hz between 2 kHz and 200 kHz offset (Fig. 1). This phase noise is only
marginally above the one of the reference OCXO, and at frequency offsets between 1 kHz and 10 kHz(which is of highest relevance for the clock
application) presents an improvement by up to 10
dB compared to a previous version of the ASIC 1.
From the measured phase noise, we calculate thelimit to the clock stability arising from the Dickeffect to be on the level of 2×10-11 at 1 second.
The previous ASIC version was used as
microwave synthesizer in a CPT clock setup basedon a DFB laser and a micro-fabricated Cs vapor
cell.
The measured
clock stability is< 4×10-10 -1/2 up to =10s, currently limited by themodulation scheme.

Fig. 128: Phase noise of the 4.6 GHz signal
measured for the ASIC synthesizer.

Acknowledgments: this work was supported by the EU FP7 (MAC-TFC project www.mac-tfc.eu, grantno. 224132) and the Swiss National Science Foundation. We thank M. Haldimann for helpful
discussions.
380

Y. Zhao, S. Tanner, A. Casagrande and P.-A. Farine, “A 4.6-GHz, 15-mW frequency synthesizer CMOS ASIC with milliHertz frequency resolution for miniature atomic clocks”, Conf. IEEE Int. Freq. Control Euro. Freq. Time Forum, pp. 1- 4,
May, 2011.

IFCS-EFTF2-PCD2-4

Reducing the time transfer uncertainty in the fiber optic time andfrequency dissemination system
Wojciech Słowik1
1

Department of Electronics, AGH University of Science and Technology, Krakow, Poland
Email: wslowik@agh.edu.pl

In last years our group is developing the fiber optic system for accurate time and frequency (T&F)
dissemination381,382,383. The main idea is to actively stabilize the propagation delay of the link byorganizing a delay locked loop (DLL) system, using the feedback signal from remote side of the system.
The core element of the hardware is a set of two precisely matched electronic delay lines, fabricated as
an application-specific integrated circuit (ASIC). In the current realization mismatch of the tuning
characteristics of the delay lines is about 30 ps, and it affect the overall T&F dissemination accuracy andstability1,2.
In this work we present a newly designed compensating module, which reduces the delay mismatch(Fig. 1). In the poster we will show the measured results of the compensation efficiency, both in nominal
temperature, and for  5C temperature excursions. We find the remaining mismatch as no greater than
3 ps. After applying the compensation module, the problem of the delay lines mismatch go below otherfactors limiting the overall system performance.

Fig. 129: General concept of compensating module for active stabilization of the delay381

Ł. Śliwczyński, P. Krehlik, Ł. Buczek, and M. Lipiński, “Active propagation delay stabilization for fiber optic frequency
distribution using controlled electronic delay lines,” IEEE Trans. Instrum. Meas., vol. 60, no. 4, pp. 1480–1488, Apr. 2011.
382

P. Krehlik , Ł. Śliwczyński , Ł. Buczek , M. Lipiński,: Fiber-optic joint time and frequency transfer with active
stabilization of the propagation delay; IEEE Transactions on Instrumentation and Measurement383

Ł. Śliwczyński, P. Krehlik, A. Czubla, Ł. Buczek and M. Lipiński, “Dissemination of time and RF frequency via astabilized fibre optic link over a distance of 420 km”, Metrologia 50, 133-145, 2013.

IFCS-EFTF2-PCD2-5

Research on Hybrid-compensation technology for reducing
acceleration sensitivity of TCXO
Liangpeng Chen1, Qingxiao Shan1
1

National University of Defence Technology, Changsha,Hunan,China

Email: tsingxiao@163.com
Temperature compensated crystal oscillator (TCXO) is widely used in GPS receiver for its small
size and low cost. But GPS receiver often used at mobile devices such as aircraft and missile whichsuffer from serious vibration. The g sensitivity of TCXO decrease the frequency stability and deteriorate
the performance of GPS receiver. To reduce the g sensitivity, the way used prevalently is mechaniccushion but it is not efficient at low frequency vibration below 300Hz,as shown in fig.1. This paper
proposed hybrid-compensation which is made up of electronic compensation and mechanic cushion. The
electronic compensation aims at low frequency vibration while mechanic cushion aims at highfrequency. The electronic compensation comprised of a MEMS sensor ,a digital controller and a D/Aconverter is with low cost and small size due to high integrate of digital device. The volume of mechaniccushion can be with small size for it only aims at high frequency.The method proposed can reduce the gsensitivity and improve reliability of TCXO by adding extra devices to the original TCXO.
A

Vibration-1

mechanic
damping
After mechanicalcompensation
Vibration frequencyA

f1  300Hz
Vibration-2
mechanic
damping
After mechanicalcompensation

Vibration frequency f 2  300 Hz
Fig.1: The effect of Mechanical compensation under different vibration frequency

IFCS-EFTF2-PCD2-6

Demonstration of doubly rotated X-cut quartz plate
oscillators with a slot vibrating in length extensional mode
Tomiharu Yamaguchi, Kiyoto Katakura, Yusuke Todo, Hisashi Kanie
Department of Applied Electronics, Tokyo University of Science, Katsushika, Japan
Email: t-yama@te.noda.tus.ac.jp
We analyzed doubly rotated X-cut quartz plate oscillators with a slot in the resonator vibrating
essentially in length extensional (LE) mode by FEM and fabricated oscillators monolithically by the wet
etching process. To reduce the series resistance R1 and increase the quality factor Q, two rotation anglesof the doubly rotated X-cut plates (XYlt) with an aspect ratio w/l = 920/2000 were varied in the region
from 0°/0° to −60°/−10°384. The rotation on the Y-axis of an X-cut plate allows to use a wet etchingprocess to fabricate a complex shape oscillator consisting of a resonator, supports, and a mount (Fig. 1).
The negative rotation angle around the X-axis increases the positive value of the first order temperature
coefficient α caused by the mixture of flexure mode. The slot at the center of the resonator dampens thedisplacement at the long sides of the resonator by the vibration in both LE and flexure modes thatprevent the resonator from being supported at the middle of the sides. The resonator was supported at
the points 40 μm off-center where the total displacement becomes almost zero.
A fabricated doubly rotated X-cut quartz plate (XYlt) −35°/−1° oscillator showed the frequencytemperature characteristics with α = −0.6 ×10−6 /°C, the second order temperature coefficient β = −3.5
×10−8 /°C2 (Reference temperature T0 = 20°C) as shown in Fig. 2. The parameters of the electricalequivalent circuit of the oscillator measured in the air are the followings: R1 =1080 Ω, the series
inductance L1 = 2.70 H, and the capacitance ratio r = 192 at Q =19000.

Fig. 130: Schematic diagram of the designed quartz
resonator.

384

Fig. 131: Frequency-temperature characteristics ofthe fabricated quartz resonator (α = −0.6 ×10−6 /°C,
β = −3.5 ×10−8 /°C2).

IEEE Standard, “IEEE Standard on Piezoelectricity”, 176-1987.

IFCS-EFTF2-PCD2-7

Investigation into Spectrum Shape Fluctuations of Oscillators andSignal Sources
Michael Underhill1
1

Underhill Research Ltd, Lingfield, UK
Email: mike@underhill.co.uk

Spurious ‘spikes’ or ‘spurs’ can be observed in the spectra of oscillators and signal sources using both
analogue and digital spectrum analyzers Some tentative explanations for the occurrence of these spurs
and related phase and frequency jumps have been put forward385,386. The fluctuations of these in timeneed further investigation so that some theory for them may be constructed.
Also the spectrum shape of an oscillator may vary with time both symmetrically, corresponding to pureamplitude, or pure phase, noise and fluctuations, or asymmetrically, corresponding to a mixture of
amplitude and phase noise and fluctuations387. A software receiver, such as the RFSpace SDR-IQ, canact as a versatile digital spectrum analyzer and with suitable signal processing software, such as
SpectraVue, can give a ‘time-waterfall’ display of the spectrum. For example the spectrum shape can beseen at the top of Fig. 1 with a 50s time (colored)waterfall below.
The Leeson Model388 of an oscillator can be and isextended to investigate the factors that can cause
fluctuations in spectrum shape with time. The
amplitude limiting process always present inoscillators provides a total energy constraint on theoscillator but it does not exactly define the spectrum
shape. Energy may be coupled and exchanged
between one part of the spectrum with another. The(new) proposition that is incorporated in theinvestigation is that sideband components are lightly
coupled by an amount that is also frequency spacing
dependent.
Some further results to extract, define, validate andcalibrate suitable proposed theory will be presented.

385

Fig. 132: A 2kHz Spectrum with 1dB amplitude
scale steps at top, and ‘time-waterfall below, of a
3520kHz DDS signal, showing fluctuating ‘spurs’
in the 50s time-waterfall using ‘rectangle’
windowing, and a 4Hz resolution bandwidth.

M. J. Underhill, “Fundamental Phase Jumps in Oscillators?” Proc 20th EFTF, Braunschweig, Germany, 2006

386

M. J. Underhill, “More fundamental instabilities in oscillators?”, 15th EFTF’09: IEEE-IFCS’09, Besancon, France, 20-24
April 2009, pp 334-337.
387

M. J. Underhill., “Time jitter and phase noise — Now and in the future?” IEEE International Frequency Control
Symposium (FCS), p1-8, 2012.
388

D. B. Leeson, “A simple model of feedback oscillator noise spectrum,” Proc. IEEE, 54, No. 2, 1966, pp. 329-330.,

IFCS-EFTF2-PCD2-8

All-Digital Video RF Transmitter with Embedded
Direct Digital Frequency Synthesizer
Konstantinos Vasiliou1 , Kostas Galanopoulos1 , Paul P. Sotiriadis1
1

Department of ECE, National Technical University of Athens, Greece
Email: costas290a@gmail.com

This work presents an all-digital PAL video RF transmitter with embedded all-digital frequency
synthesizer for the generation of the carrier. Converting traditionally analog to equivalent digital circuits
and systems has been a major trend the past few years due to the automation and fabrication advantagesof digital integrated circuits vs. analog ones, especially in deep-sub-micron integrated circuits
technologies. The proposed topology can be easily implemented in FPGAs or ASICs providing analternative to popular analog-RF ones and offering extremely fast concept-to-market time, versatility,
low cost, minimal chip-area and power requirements.

FCW

n-1

Phase
Accum
ulatornn

Phase
Dithering

Sine
Look-up
table

n

n

2n
Multiplier

8
CameraFrame
Buffer

n

PAL
FSM

n

LPF

n

Out
1-4 MSBnFig.1 DDS-based all-digital PAL video RF transmitter architecture using a 1 to 4 bit Sigma-Delta DAC

The architecture used is illustrated in Fig. 1. An 8-bit image signal is captured by a digital Video camera
and is temporarily stored in a RAM frame buffer. It is then accessed and encoded to a composite PAL
signal. Using a digital multi-bit-output phase-dithered DDS we generate an n-bit carrier signal wherephase-dithering is mainly used to reduce the size of the sin look-up table. AM modulation is thenimplemented by multiplying the carrier with the DC-shifted composite data stream. Using digital
amplitude dithering389 the modulated RF signal is converted to 1 to 4 bits (programmable) via a sigmadelta DAC.
The presentation of the paper will be accompanied by a live demo (Fig.2) of
the proposed architecture. For this purpose an all-digital televisiontransmitter has been implemented on an FPGA board (Papilio One / Xilinx
Spartan 3E). This entry level FPGA (Xilinx 3E XC3S250E) has anequivalent of 250K gates and only 216K of Block RAM bits. For video Fig. 2: Footage from thecapturing we use the Omnivission OV7670 VGA camera and the PAL video FPGA-based PAL VideoRF transmitter
signal is transmitted at VHF television channel 2 (48.25 MHz).
389

K. Galanopoulos, P. Sotiriadis, “Optimal Dithering Sequences for Spurs Suppression in Pulse Direct Digital
Synthesizers”, IEEE International Frequency Control Symposium 2012.

IFCS-EFTF2-PCD2-9

Theoretical and experimental investigations on 1/f noise of quartz
crystal resonators
Ghosh Santunu1, Sthal Fabrice1, Imbaud Joel1, Devel Michel1, Bourquin Roger1, Vuillemin Cedric1,
Bakir Ahmed1, Cholley Nathalie1, Abbe Philippe1, Vernier David1, and Cibiel Gilles2
1

FEMTO-ST Institute, UFC, CNRS, ENSMM, UTBM, Besançon, France2
Microwave and Time-Frequency, CNES, Toulouse, France
Email: fsthal@ens2m.fr

The Centre National d’Etudes Spatiales (CNES), Toulouse, France and the FEMTO-ST Institute,
Besancon, France, have initiated investigations on the origins of noise in bulk acoustic wave resonators
together with several European manufacturers390. Theoretical and experimental works are reported inthis paper.
We first improve on our previous study using fluctuation dissipation theorem by adding a term forinternal damping391 to the classical wave equation already studied392. This allows us to recover a 1/fnoise spectral density at low frequency. The level of this 1/f noise is governed by a single fitting
parameter that can be connected to the onset frequency of this 1/f regime. It constitutes the fundamental
intrinsic limit of quartz crystal. Some preliminary considerations on the physical origin of this parameterin terms of microscopic processes in the crystal are given.
Experimentally, quartz crystal resonators have been cut from a quartz crystal block supplied specificallyfor this study on 1/f noise. The reader is reminded of the description of the blank realization and the
topology of the resonator prototype is exposed. The resulting resonators are SC-cut with a 5 MHz
resonant frequency. Then, we report noise measurements made on these quartz crystal resonators using apassive phase noise measurement system. The short-term stabilities of several resonators have beenmeasured to be lower than 810-14. A comparison of these resonators is given and the results are
discussed according to the position of the resonators inside the crystal block.

390

F. Sthal, S. Galliou, J. Imbaud, X. Vacheret, P. Salzenstein, E. Rubiola, G. Cibiel, "About Quartz Crystal Resonator
Noise: Recent Study”, Proc. ICNF, Pisa, Italie, 15-19 June, pp. 607-610, (2009).
391

G. I. Gonzalez and P. R. Saulson, "Brownian motion of torsion pendulum with internal friction," Phys. Lett. A, vol. 201,
pp. 12-18, May 1995.
392

M. Devel, R. Bourquin, S. Ghosh, J. Imbaud, G. Cibiel, F. Sthal, "Quartz crystal resonator noise and fluctuationdissipation theorem considerations", Proc. IEEE Int. Freq. Cont. Symp., Baltimore, Maryland, 22-24 May, pp. 425-429,(2012).

IFCS-EFTF2-PCD2-10

Switching Down-Converting RF Mixer with Embedded
Single-Bit-Output All-Digital Frequency Synthesizer
Nikos Stamatopoulos1, Kostas Galanopoulos1, Paul P. Sotiriadis1
1

Department of ECE, National Technical University of Athens, Greece
Email: nstam@ieee.org

This work proposes a switching down-converting RF mixer with an embedded single-bit-output alldigital frequency synthesizer, an architecture having the advantages of digital circuit design (portability,
reconfigurability, automated checking and verification), compared to traditional analog solutions, inboth ASIC and FPGA implementations.
Although switching mixers are popular in discretecomponent designs393 and have been implemented in
RFICs394, they are typically driven by classical PLLs orcomplex mixed-signal frequency synthesizers. The proposed
mixer is based on digital transmission gates which are driven
directly by the single-bit output stream of the embedded alldigital frequency synthesizer. Dithering techniques are used
to make the synthesizer’s spectrum sinewave-like andconvert spurs to continuous noise floor395. The paper
elaborates on the mathematical estimation and measurementsof the mixer’s spectrum.
Our test setup, serving as a proof of principle, consists of themixer whose transmission gate is controlled by the all-digitalfrequency synthesizer implemented in a mini FPGA board(XuLA-50 / Xilinx Spartan 3A). Both the low-cost off-theshelf transmission gate (with on/off switching time ~ 5ns)
and the low-cost FPGA limit the frequency of operation of
the mixer to a few tens of MHz. The RF signal at
f RF  20 MHz is provided by the signal generator while thesynthesizer’s output frequency (LO) is f LO  21.2 MHz .
The mixer’s output spectrum 0-50MHz is shown in Fig. 1 as
well as in Fig. 2 which is centered at the desirable output
component at f LO  f RF . The conversion loss, LO/RF
isolation, RF/IF isolation and input IP3 are estimatedanalytically and measured experimentally. Further
measurements at higher frequencies are also presented in thepaper.
393

Fig 133: Switching mixer with embedded
all-digital frequency synthesizer

Fig 2: Switching mixer’s output

Fig 3: Spectrum centered at f LO  f RF

U.L. Rohde, Microwave and Wireless Synthesizers: Theory and Design, Singapore: Wiley-Interscience, 1997.

394

Robert B. Staszewski et al, "All-Digital PLL and Transmitter for Mobile Phones", IEEE Journal of Solid-State Circuits,Vol. 40, No. 12, December 2005.
395

Kostas Galanopoulos, Paul P. Sotiriadis, "Optimal Dithering Sequences for Spurs Suppression in Pulse Direct Digital
Synthesizers", IEEE International Frequency Control Symposium, 2012.

IFCS-EFTF2-PCD2-11

433 MHz Wide-tunable High Q SAW Oscillator
Tsubasa Yasuda+, Shasika Shaminda Senanayaka++,
Shyoji Izumiya, and Takehiko Adachi *Division of Electrical and Computer Engineering
Yokohama National University
Yokohama, Japan* Email: ada@ynu.ac.jp
A piezoelectric resonator, as a quartz crystal resonator and a SAW resonator, is widely used in a
voltage control piezoelectric oscillator. Recently, demand for wide tunability and low phase noise of apiezoelectric voltage controlled oscillator has been increasing. But the frequency tunable range is limitedby the capacitance ration of a piezoelectric resonator within a few hundred ppm. And, the phase noise ofa piezoelectric oscillator is mainly determined by the effective quality factor of a piezoelectric oscillator,
degraded from the piezoelectric resonator’s unloaded quality factor. The dual-T quartz crystal resonatorcircuit was developed as the wide-tunable resonator circuit
having quality factor comparable with the component
piezoelectric resonator. We showed wide-tunability andquality factor enhancement method of a dual-T circuit,using 10 MHz crystal resonators.
In this paper, we have developed a 433 MHz dualT SAW oscillator. Figure 1 shows the schematic diagramof the oscillator. The oscillator is made of an amplifier,Fig. 134:.Dual-T SAW oscillator.
variable gain amplifiers, phase shifters and dual-T SAW
resonator circuit. Oscillation frequency can be changed bycontrolling the gains of variable gain amplifiers. The
effective quality factor of the oscillator is enhanced byadjusting phase shifts. Figure 2 shows the measured
frequency tunability. Measured frequency tunable range isabout 1,700 ppm, exceeding the limit restricted by used
SAW resonators. The effective quality factor of theFig.
2:Measured
frequency
oscillator was obtained by measured open-loop voltage
tunability.
transmission function. The obtained effective quality factorof the oscillator is about 30,000, about three times of theunloaded Q of SAW resonators. Figure 3 shows themeasured spectrum at the center frequency of the frequency
tunable range. Phase noise of the oscillator is estimatedfrom the measured spectrum. Above 6 dB improvement ofphase noise is obtained at 1kHz offset frequency comparedto that of a colpitts oscillator.
+

He will join AISIN COMCRUISE Co., Ltd. on 1 April,
2013.

++

He is working for NIHON DEMPA KOGYO Co. Ltd., now.

Fig. 3: Measured spectrum at the center
frequency of tunable range.

IFCS-EFTF2-PCD2-12

Tracking DDS in Time and Frequency Metrology
C. E. Calosso1
1

Optics Division, INRIM, Torino, Italy.
Email: c.calosso@inrim.it

The Phase-Locked Loop (PLL) in electronics was introduced in early 1930s to surpass thesuperheterodyne technique in radio receiver396. Since then, its diffusion has been very wide: intelecommunication, in digital electronics, in motor controls… and also in time and frequency: indirect
frequency synthesis, clean-up and tracking oscillators, phase noise measurement, but also comb
stabilizations, laser locks or even fiber link compensation.
In time and frequency applications, the interest is mainly directed to the output of the locked oscillator,
considered as a filtered or frequency multiplied replica of the reference signal. This is inherently due tothe poor performance of the controlled oscillator that, for long measurement time, is worse than the
input one that is considered, for this reason, the PLL reference (fig. a).
Input
Reference

Input

Servo

sin2 0i t  i 

Servo

Digital output

 0i or  i

DDSContolled
Oscillator
Reference

OutputFig. a: Typical PLL.

Analog output

Fig. b: Tracking DDS.

By replacing the controlled oscillator with a Direct Digital Synthesizer (DDS) (fig. b), it is possible toreverse this point of view: now the local oscillator, the DDS referred to a stable and accurate clock, canbe better than the PLL input that now takes on the meaning of measurand instead of reference. In thismanner, the PLL can be used not only as generator, but also as frequency and phase meter, simply
considering the corrections applied to the DDS to track the input. The inversion of the usual approach to
PLLs, joined with DDS qualities397, opens new possibilities in the time and frequency field because
leads to a compact, low noise, cheap, wide input range, real time, digital phase/frequency meter that canbe used in a wide range of applications.
At the conference I will expose the key points to correctly implement this scheme and reach the ultimate
limit, represented by the DDS residual phase noise. On the opposite, I will discuss how to deal with highnoise input signals as those encountered frequently in the growing field of optical frequency metrology.

396

de Bellescize, Henri (June 1932), "La réception Synchrone", L'Onde Electrique 11: 230–240.

397

C. E. Calosso, Y. Gruson, E. Rubiola, “Phase noise in DDS,” Proc. 2012 IFCS p. 777–782.

IFCS-EFTF2-PCD2-13

A miniature timing microsystem using two silicon resonators
David Ruffieux1, Jacek Baborowski1, Nicola Scolari1, Thanh C. Le1, Antti Jaakkola 2, Tuomas Pensala2,James Dekker 2, Charles A. Manier3 , Kai Zoschke3, Hermann Oppermann3
1

CSEM, Neuchâtel, Switzerland
2
VTT, Espoo, Finland
3
Fraunhofer IZM, Berlin, Germany
Email: dru@csem.ch
This paper presents a miniature timing microsystem based on a pair of co-integrated low and highfrequency silicon resonators -430kHz and 26MHz respectively- so as to implement an accurate, lowpower, temperature-compensated real time clock (RTC) and to generate reprogrammable clocks between
1-50MHz in a reconfigurable way.

Frequency deviation [ppm]Legacy quartz crystals have recently continuously beenchallenged by the announcement of new products relying
on silicon MEMS resonators for either programmable HF
clocks generation398 or to implement RTCs399. The noveltyof this work resides in the compact implementation of both
functions using a pair of co-integrated
piezo-electrically
Digital TCFSM+REG+I2C+RTC OTP
8x32b
driven silicon resonators. A temperature compensated
32,768Hz clock further driving the RTC sub-circuit is
HF
LF & RCRF
LC
generated by frequency interpolation and fractional division
OSC
OSC
DIV
VCO
1V6
PFD
of the signal of a 430kHz electro-mechanical oscillator. The
1V LDOLDO
CP LF
temperature information is obtained periodically by turning
on a mostly linear temperature sensitive 10MHz RC
oscillator whose periods are counted over a time window Fig. 135: Photos of ASIC and dual resonatordefined by the low frequency MEMS oscillator. An on-chip1500
state machine using calibration data stored in a non-volatile1000
one-time programmable memory then calculates andth500
updates the compensation parameters using a 4 orderpolynomial fit. Any of the above clocks can be made0
available externally on demand or when an IRQ is-500
dfH
generated in the RTC via its timer, alarm or time stamping
dfL
-1000
dfc_div
request.
-1500
-50
-25
0
25
50
75
The 26MHz high frequency silicon resonator temperature
Temperature [°C]compensation is implemented indirectly via the same statemachine by adjusting the fractional-N divider ratio of a Fig. 2: LF oscillator temperature stability
2GHz PLL whose RF output is further divided by an integer
and/or fractional divider(s) to produce up to two programmable clocks of unrelated frequencies. Fig.2.
shows a measurement of the temperature stability of the low frequency MEMS-based oscillator with andwithout compensation. The system draws 2A in RTC mode and 4mA when HF clocks are generated. It
achieves ±20ppm stability with a 3-points trim.

398

http://www.sitime.com/products/low-power-oscillators/sit8008

399

http://www.maximintets/low-powegrated.com/datasheet/index.mvp/id/6861

30
20
10
0
-10

-20
-30

IFCS-EFTF2-PCD2-14

Background, Motivation and Objective:
One of the issues facing many types of oscillators is the transference of stress from the external world
through the die to the resonator. Typically, resonators are clamped at more than one location. Integrated
FBAR oscillators (referred to as FMOS1,2), uses a resonator that is clamped on all sides and integrated
into an all-silicon, chip-scale package with integrated circuits. Mounting FBAR oscillators (epoxy die
attach, over-molding and soldering) onto a customer board exposes the FBAR oscillator to stresses that
occur during the assembly, plus additional stresses that occur during use. Although applied stress willchange frequency of the resonator, it is hard to quantify. This paper does a first cut model of the stresses
and then matches that to the changes in the measured frequency. Next, we discuss several designs that
help mitigate the effect of external stresses on the resonator.
Statement of Contribution and Methods:
We use a ‘Plan of Record’ (POR) FBAR resonator that follows the design rules used in high volume
FBAR manufacturing and then study the effects of stress on the resonator/oscillator frequency whenthousands of die on a wafer are subjected to an external stress. This stress is modeled and from that, wematch the modeled in-plane stress (and spatial wave form across wafer) to measured frequency shifts asmeasured over thousands of die across wafer. We then compare the mean and standard deviation andmaximum stress for 3 types of resonator designs; the POR and two kinds of stress relieved resonators(SRR).
Results/Discussion:
The experiment consisted of measuring the frequency of thousands of oscillators on a 6” wafer(mounted on a vacuum chuck) and then re-measuring of the same die, where the wafer was removed andthen placed on top of a thin Mylar substrate 57 mm in diameter – all on the same vacuum chuck. The
resulting plot of the change in frequency (using false colors) highlights clearly the shape of theunderlying piece of Mylar and the resulting stress created by the bending of the wafer due to the wafer
being held by the vacuum around the edges. From this and with modeling, we conclude that we are
getting about 0.8 ppm/MPa shift in frequency due to in-plane stresses. The figure shows the plots of ffrequency for 3 types of resonators, a POR resonator, and two designs of stress relieved resonators.
1)
2)

R. Ruby et al., “Positioning FBAR Technology in the Frequency and Timing Domain”, Trans. Ultrasonics.
Ferroelectrics, and Freq. Control (TUFFC), v. 59 #3, March 2012, pp. 334-345
R. Ruby M. Small, “Packaged Device with Acoustic Resonator and Electronic Circuitry and Method of making thesame”, Pub. # US 2012/0075026 A1, Pub. Date: March 29 2012

IFCS-EFTF2-PCD2-15

New thermal design to develop excellent stability
and ultra low power compact OCXO.
Kamalkumar S#, Mariyappa Chandrashekar*, M Brahmananda Reddy,
Varaprasad Rayudu, Nalini C V#

R and D Deportment Centumrakon India pvt ltd. Bangalore
kamalk@centumrakon.com

Abstract— Due to the cost, power and size constraints, improvements are made by introducing new thermal design, which has beendeveloped to achieve compactness, low power and excellent stability OCXO.
Power consumption and stability are both closely related to the size of the entire OCXO package. During last year’s,
making the oven smaller in order to affect a quicker warm up and will reduce frequency stability, as the smaller mass is more
responsive to ambient temperature fluctuations. However, making the oven larger for better frequency stability will raise theamount of power required to maintain oven temperature. In order to achieve high frequency stability verses temperature, lowpower consumption and compact package with low cost, new thermal design and a radical new oven’s design is worked out.
This paper demonstrates a new thermal layout design to achieve excellent frequency stability verses temperature by
ensuring thermal conduction and convention paths are small and thermal gradient between the crystal, sensor and criticalcomponents are very less, the component selection has done in such a way that the thermal exchange between the criticalcomponents induced is linear and the temperature set point is compared with the actual value measured by the sensor and error
signal is amplified and converted into a current controlling the heating elements. With reference to series of trails conducted byvarying the crystal drive level, stability over the temperature has still improved by optimising the drive level. The details
illustrations are clearly explained in this paper.
In this design the new heating mechanism has introduced and the PCB area is reduced to inducing low power dissipationin the circuit of less than 0.8W. Cost has been reduced by using HC43 crystal and single oven structure with smaller package. This
paper presents development of single oven for excellent frequency stability, low power and compact package OCXO.
The achieved main parameters of new thermal design OCXO model are: Frequency 10MHz, frequency stability less than ±1.5ppb
at -40 to 80°C. A SC-cut HC43 crystal with optimized drive level strengthens our aspect of low power consumption less than 0.8W
and package style is 36×25×10mm3.

Fig1. OCXO assembly.

Fig2. PCB structure.

IFCS-EFTF2-PCD2-16

Electronic Signal Transduction in Collectively-Sensed Arrays of
Parallel Piezoresistive NEMS Resonators
Hamidreza Zamani1, Philip X.-L. Feng1
1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
Email: hamidreza.zamani@case.edu.edu, philip.feng@case.edu

NEMS resonators based on piezoresistive (PZR) nanowires and nanocantilevers are among the mostinteresting high-speed nanosensors. While it is desirable to use NEMS arrays400,401, today’s works have beenvery limited, and very little has been studied in analyzing and modeling the fundamental limits in signaltransduction for integration of PZR NEMS arrays with CMOS. In this work, we focus on parallel arrays of
PZR NEMS with single CMOS readout circuit.
We first investigate electromechanical modeling of a prototype PZR NEMS with both series and parallel
PZR resistors (Fig. 1a). We have developed a comprehensive and precise equivalent circuit (Fig. 1b) forsuch systems. Then, using analytical formulas, we discuss that the noise voltage power (due to CMOS,(NEMS resonator and PZR noise sources) is approximately) for the case of NEMS-CMOS co-integration and() for thecase of off-chip integration with, Cg the total shunt capacitance at
MOS gate, BWNEMS the bandwidth of the NEMS, and Δf the frequency range over which noise and signal
power are calculated. The above equations show that SNR will increase by a factor of either N or N2 basedon gm value of the readout circuit. The analytical results verified by Cadence simulations (Fig. 1c) givedesigners a means to better co-design PZR NEMS arrays and CMOS readout circuits.
VDD
M

(a)

VDD

(b)

seriespiezoresistors

parallelpiezoresistors

R0

actuation
electrode

SNR (dB)

vDC2
+vPZR

85.0
80.0
75.0
70.0
65.0
60.0
55.0

(c)

+

vact

+
-

-

PZR-NEMS-CMOS Cointegration
CPCB=1 pF Shunt Capacitor

Lm

I2n,ZmRm

Cg

Cm

CPCB=10 pF Shunt Capacitor

R0+ΔR

R0-ΔR

vDC2
-vg

vDC2
+vg

vDC1
vs
1

2
3
5
Number of Parallel PZR NEMS

10

2R0+ΔR'

I2n,PZR-+

vDC2-vPZR -

Lw1

vact

R0 R0 2
( )
2 ΔR
αvs

on-chip (IC)

V2n,M
+

Lw2
CPCB

-

Zm

off-chip (IC)V2n,series,PZR+ 2R0-ΔR'

Cp

M

Cin,M

R0
2
vg ΔR
R0

vDC2

Fig. 136: (a) Illustration of piezoresistive (PZR) NEMS unit used for electromechanical modeling. (b)Equivalent circuit of (a) connected to the CMOS circuit. Both on-chip and off-chip parasitic capacitances aswell as bonding wires (in case of PCB integration) are also shown. (c) Cadence simulation results for SNR
of PZR NEMS arrays with CMOS integration.

400

M.U. Demirci, C.T.-C. Nguyen, “Mechanically corner-coupled square microresonator array for reduced series motional
resistance”, in Digest Tech. Papers, Transducers’2003, 955-958, Boston, June 8-12 (2003).
401

I. Bargatin, E.B. Myers, J.S. Aldridge, C. Marcoux, P. Brianceau, L. Duraffourg, E. Colinet, S. Hentz, P. Andreucci, M.L.
Roukes, “Large-scale integration of nanoelectromechanical systems for gas sensing applications”, Nano Letters, 12, 12691274 (2012).

IFCS-EFTF Group 3 poster session 2
Forum Hall
Wednesday & Thursday, July 24-25, 2013, 1:00 pm - 2:00 pm and 3:30 pm - 4:30 pm
Chair:

John Kitching
NISTIFCS-EFTF3-PCD3-1

Estimates Of Achievable Frequency Stability Values In Atomic
Gas Cell Frequency Standards With Coherent Population
Trapping
V.S.Zholnerov1, K.A.Barantsev2, I.M. Sokolov2, A.N.Litvinov2
Russian Institute of Radionavigation and Time, St.-Petersburg, Russia
2St.-Petersburg State Polytechnical University, St.-Petersburg, Russia
Email: zholnerov@mail.ru

1

Use of coherent population rapping effect in atomic gas-cell frequency standards enables one, on one
hand, to drastically reduce standard’s dimensions due to the refusal from using a microwave cavity and,on the other hand, to improve a frequency stability of such standards.
The frequency stability values achieved in chip-scale atomic frequency standards developed by various
companies are well known. It seems to be necessary, however, to estimate potentially achievable valuesof frequency stability, taking into account actual fluctuation performances of frequency standard’s
physical package assemblies and electronic circuitry when a selection of the physical package mode is
optimal.
The frequency stability values achieved in rubidium gas-cell frequency standards of a traditional typeused aboard GPS/Galileo satellite are also well known. The further improvement of these devices can berealized through using a coherent population trapping effect with double-frequency laser emissionxix.
The paper is dedicated to the investigation of frequency stability values achievable in atomic gas-cellfrequency standards when using Rb87 D-1 line with buffer gases in coherent population trappingxx,xxi,xxii.
Estimates of frequency stability are performed using a computer program for multi-parametric
optimization as regards parameters of the physical package and frequency-lock loop of the controlled
crystal oscillator. Estimates produced for a gas cell of standard dimensions show a possibility to achievedailyfrequency
stability
at
level
of
(2÷3)10-15. For a chip-scale atomic frequency standard, frequency stability over 1-hour measurement
interval could achieve a value of (2÷3)10-12 with the appropriate selection of parameters as regards
physical package and electronic components.

IFCS-EFTF3-PCD3-2

Outlook of Developing the Absorption Cells with Double Anti-Relaxation Components(Coating + Buffer gas) for Improving a Long-Time Stability of Atomic Frequency
Standards and Quantum Magnetometers
E. Pestov1

The Fed. State Scient./Prod. Ent. "Geologorazvedka", 19/1 Knipovich str., St.-Petersburg 192019
Russian Institute of Radionavigation and Time, RIRT, 2 Rastrelli sq., St.-Petersburg 191124, Russia
E-mail: infra-balt@peterlink.ru

2

The

Use of absorption cells with anti-relaxation wall (ARW) coating by high-molecular paraffins was
extremely fruitful for creating the quantum magnetometers of various purpose in the USSR - from mass
application in geophysics when exploring mineral resources up to space units installed on ‘Cosmos-321’
and ‘Cosmos-355’ satellites (1969 and 1971). In these magnetometers the quantum sensors were moved
to a distance of 8 m from the satellites using a rod and operated under open space conditions.
During the same years, extensive studies were performed with respect to Zeeman’s resonance frequency
shifts in cells with ARW-coating and dependencies were established between systematic errors for all
used alkali atoms - 133Cs, 85Rb, 87Rb, 39K, 41K - and various parameters of optical pumping (A. Kozlov,
E. Pestov - IZMIRAN, Troitsk, Moscow). In particular, it was established that, when increasing a celltemperature from 35 to 55°C, Zeeman’s resonance frequency, ω0, decreased.
Application of cells with ARW-coating for atomic frequency standards was retarded due to an opinion
on the insufficient stability of coating properties over time, which could result in non-reproducibility ofa standard’s frequency from one switch-on to another. The result of recent works [1], including also thiswork, can, however, significantly change this situation. The authors of work [1] have demonstrated atechnique for relaxation processes’ stabilization on coating surface which resulted in 87Rb standard’s
frequency stability improvement.
The proposal of Dr. G. Mileti to the author of this work seems to be interesting: the case in point is theadvisability to add a buffer gas of low pressure into the cell with ARW-coating which could improve theparameters of a quantum device. This work is just dedicated to this problem.
Following processes are investigated in this work:
1. Dynamics of synchronous relaxation of magnetization Mz- and Mx- components at Zeeman’sresonance frequency, ω0 [2] in 87Rb-cell (ARW-coating + buffer gas, Ar) when changing a celltemperature, t°C.
2. Dynamics of a frequency shift, δν (t°C) of the hyperfine 0-0 resonance at frequency, ν0-0 ~ 6,834 GHz.
As a result, following is fixed.
In the vicinity of some temperature, t*(°C), a break in the relaxation dependence between coherence
Zeeman’s Mx- component (τ2) and cell temperature occurs.
The growth of a negative ‘0-0’resonance frequency shift, (– δν), from relaxation action on the coating
surface is slowing down with temperature growing, and in the vicinity of the same temperature value,t*(°C), a temperature -frequency coefficient becomes equal to zero due to the compensating action of thevolume 87Rb-atoms’ relaxation within a buffer gas.
In such a way, addition of a buffer gas with a positive value of the frequency shift, (+δν), into a cell with
ARW-coating enables one to realize a zero temperature -frequency coefficient in the vicinity of sometemperature, t*(°C), and improve standard’s long-term frequency stability.
__________________________________
1

М. Pellaton, C. Affolderbach, G. Mileti, et. al. Proc. Joint Conf. of the IFGS-EFTF, Gothenburg, Sweden,
pp. 87-90, 2012.
Pestov. Proc. Joint Conf. of the IFGS-EFTF, San. Fransisco, California, USA, pp. 623-627, 2011.

2

E.

IFCS-EFTF3-PCD3-3

Measurements of optical frequency shift in sealed Cs vapor cells filled with He, Xe buffer gases
E. Kroemer, V. Giordano, R. Boudot
FEMTO-ST, CNRS, 26 chemin de l’épitaphe 25044 Besançon cedex, France.
Email: rodolphe.boudot@femto-st.fr

FEMTO-ST developed an original technology for filling and fabrication of Cs vapor microfabricated cells filledwith buffer gas [1]. A great originality of this method is that Cs vapor is generated after the complete sealing of
the cell by laser activation of a Cs dispenser developed by SAES Getters. Additionally, we pointed out thepossibility to cancel the temperature-dependence of the Cs clock frequency at a temperature inversion of about
80°C using a single Ne buffer gas [2]. In this single gas configuration, the main advantage is that the so-called
inversion temperature where the Cs clock will typically operate does not depend on the buffer gas pressure. At the
opposite, this single-gas cell configuration prevents the clock to operate at high ambient temperature (typicallyabove 100°C) without the use of a power-consuming Peltier element to cool down the cell. This can be an issue
for the development for low-power consumption chip scale atomic clocks devoted to be used in applications withstringent and severe environmental conditions. Moreover, we observed that N2 buffer gas can not be used with ourcell technology because this gas reacts and is absorbed by zirconium compound of the Cs dispenser. This prevents
the use of a N2-Ar buffer gas mixture.
In this sense, we started a study to measure the Cs buffer gas collisional clock frequency shift in presence ofseveral buffer gas, mainly including Xe and He. Towards our objective, we decided in a first step to measure theactual buffer gas pressure in sealed cells through optical red shift measurements. The procedure is similar to theone described in [3].
We bought cm-scale commercially-available Cs cells filled with buffer gas. A physics package was developed toreceive the cells. It includes a copper cell support inside a copper oven warmed by a thin heating foil around it.
These elements are surrounded by a solenoid used to generate a static magnetic field to split Zeeman transitions.
The ensemble is inserted into a double-layer mu-metal magnetic shield.
The laser source is a 1 MHz-linewidth distributed-feedback (DFB) diode laser tuned on the Cs D1 line at 894.6
nm. The laser output is split in two directions. In the first one, the laser beam is sent through a Cs reference cellwithout buffer gas. In the second direction, the laser beam is sent through the buffer gas-filled Cs cell to be tested.
Low laser intensities (< 10 uW/cm2) are used. Optical absorption spectra from both cells are recorded with aphotodiode and fitted by a sum of four Voigt profiles. After correct calibration of the frequency axis, the opticalfrequency shift between both cells is extracted to estimate the actual buffer gas pressure in the buffer-gas-cellusing coefficients reported in [4,5].
Preliminary measurements will be reported at the conference for several cells filled with Xe or He.

[1]
M. Hasegawa et al., Sensors Actuators: Phys. A 167, 594-601 (2011).
[2]
D. Miletic et al., Elec. Lett. 46, 15 (2010).
[3]
O. Kozlova, S. Guérandel, and E. de Clercq, Phys. Rev. A 83, 062714 (2011).
[4]
A. H. Couture et al., Journ. Appl. Phys., 104, 094912 (2009).
[5] E. Bernabeu and J. M. Alvarez, Phys. Rev. A 22, 6, 2690 (1980).

IFCS-EFTF3-PCD3-4

An Accurate Measuring Method for the Transient Oscillation Frequency of Detuned Coherent
Population Trapping Atomic Clock
Daiting Shi , Yeqing Li and Zhong Wang*
School of Electronics Engineering & Computer Science, Peking University,
Beijing, 100871, P. R. China*Email: zw@pku.edu.cn
We proposes a method for measuring the transient oscillation frequency observed when Coherent Population
Trapping is excited by means of optical pumping radiation fields whose frequency difference is detuned slightly
from the ground state hyperfine frequency of the atom used. In the technique, the pumping radiation fields are
created by modulating the frequency of a laser. We call this technique Detuned Coherent Population Trapping(DCPT). Using narrow-band simulation filter and phase matching techniques this measuring method can provide
a measurement precision of about 0.5Hz. Based on this reading accuracy the DCPT atomic clocks frequency
instability can be better than 510-11/1/2 (=100s) and tend to be more stable at longer integration time. According
to our experimental results, we demonstrate that a DCPT atomic frequency standard could give good short andlong term frequency stability.
An atomic frequency standard based on the concept could be implemented by directly reading the transientoscillation caused by the detuning of the applied optical field difference from the hyperfine states transition
frequency and summing it to the microwave frequency used to modulate the laser frequency. It would eliminate
the use of a frequency-lock-loop.

IFCS-EFTF3-PCD3-5

Microwave Cavity Design for an Optically-pumped Rubidium
Atomic Beam Clock
Chang Liu, Yanhui Wang
School of Electronics Engineering and Computer Science, Institute of Quantum Electronics,
Peking University, Beijing, China
Email: wangyanhui@pku.edu.cn
Previously, most commercial clocks are based on magnetic selection, the main shortcoming of which isshort-term stability. We are developing a compact rubidium beam clock with lamp-pumping andfluorescence-detection402. Pumping and detecting lights are provided by 87Rb lamps and 85Rb filter cells.
This scheme is simple in structure and stable for long-term working. A short-term stability better thanσ(τ) = 2×10-12 ×τ-1/2 is expected. For interaction of rubidium atoms and microwave signal, a compact,
stable cavity is needed. Identically with most commercial beam frequency standards, we use a U-shapecavity with apertures at both ends. On account of size constraints, distance between the ends is about
0.2m in our scheme.
A method of constructing microwave cavity for manufactured beam clocks is discussed in this paper.
The cavity is designed in three parts, including a U-shape cavity, a vacuum window and a coaxial-towaveguide adapter. These parts are machined separately and connected with flanges. We create modelsof each part and calculate detailed dimensions with the help of ANSYS HFSS, commercial software forhigh frequency electromagnetic stimulation based on finite element method.
Several frequency offsets are related to the interrogation method, which is mainly determined by thecavity. The main causes of uncertainty related to the cavity are end-to-end phase difference, distributed
phase difference and cavity pulling effect. As a result, resonant frequency and phase difference arepriorities in the design. In addition, a tunable resonant frequency and a low loaded quality factor helps tokeep cavity pulling effect negligible.
We choose WR137 waveguide as the U-shape cavity’s arms, lengths of which are 5 halves of guidewavelength respectively. Actually, instead of bend in waveguide, two symmetrical halves of machinedcopper blocks are soldered to form a whole cavity in order to get a good reproducibility. The resonant
frequency is 6.835GHz, with a tunable range of tens of MHz. The drift length is 0.205m, leading to a
Ramsey line-width of about 600Hz. The end-to-end phase difference is below 5×10-6rad for an
asymmetry less than 0.05mm, which can be guaranteed in manufacturing. We give an estimate of thecavity’s influence on accuracy and stability in the discussion.

402

Y. H. Wang, J. Q. Huang, Y. Gu, S. Q. Liu, T. Q. Dong, Z. H. Lu, Rubidium atomic beam clock based on lamp-pumping
and fluorescence-detection scheme, J. Eur. Opt. Soc. Rapid Pub., vol. 6, 11005, 2011.

IFCS-EFTF3-PCD3-6

Extreme Resolution of the Laser Optical Pumped Alkaline Vapor
Quantum Generator
S.V. Ermak, R.V.Smolin, V.V.Semenov, P.V.Zimnitsky
Department of Quantum electronics, Saint-Petersburg State Polytechnic University,
Saint-Petersburg, Russia
Email: smolin_roman@inbox.ru
We present the results of analytic research of characteristics of self-oscillating magnetometerwith laser pumping. The mechanism of amplitude limiting is based on alkaline atom saturation effect. Thismode provides the best short-term stability of the quantum generator for average time about 100 seconds.
Exceeding of this limit causes Allan deviation of the generator operating frequency increasing due totechnical
noise
in
feedback
loop
which
spectraldensityisS δn = A f /2πωn , where A f – noise intensity constant, index n varies in range from 0.6 to 3.
Our research is based on analysis of stochastic differential equations for amplitude and frequency
fluctuations. We obtained the equations for technical linewidth of the quantum generator for different
values of n and evaluated dynamic range of relative rate of pump Г and gain of feedback k variation
within a range where generation signal has amplitude R0 (Fig.1)

Fig.1. Dependence R0 of relative parameters Г and k for one of rubidium optical transitions (represented
at three axonometric projections).
The experimental value of Af for Si photodetector has magnitude of ~10-13 Hz. After substitutionof Af and n ≈ 2 into equation for technical linewidth we get a value similar to the flicker floor
estimations for hundreds of seconds (rubidium self-generating magnetometer operating frequency is 104
Hz)403.

403

E.B.Aleksandrov, M.V.Balabas, A.K.Vershovskiy, A.S.Pazgalev. Experimental demonstration of optical pumped quantum
magnetometer resolution, JTF, 74, VOL.6, 118-122, (2004)

IFCS-EFTF3-PCD3-7

Wafer-level integration of getters in cesium-neon cells forminiature atomic clocks
M. Hasegawa1, R. K. Chutani1, R. Boudot1, V. Maurice1, L. Mauri2, C. Gorecki1, N. Passilly1
1

2

FEMTO-ST Institute, 25044 Besançon cedex, France
SAES Getters, Viale Italia 77, 20020 Lainate, Milan, Italy
Email: vincent.maurice@femto-st.fr

This paper reports on the integration of wafer-level gettering solution PageWafer® from SAES Getters
into hermetically-sealed miniature cells for MEMS atomic clocks. Its ability to sorb the gaseous residues
produced by the anodic bonding process used for sealing the cells, while preserving the required cesium
and neon atmosphere, is demonstrated.
Miniature cells are obtained by sandwiching a silicon wafer between two glass wafers bonded by anodic
bonding. First, the silicon wafer is etched-through to pattern the cavities necessary for the opticalinterrogation and the containment of a cesium dispenser. The second anodic bonding is performed underneon atmosphere (buffer gas), following the two-step process described in [404]. Once the cells sealed,
the cesium is finally released from the dispenser by local heating with a high power laser. The
PageWafer® consists in a getter film which is selectively
deposited inside 10-µm deep cavities etched on a glass wafer.
For this study, the latter was used as one of the capping wafersof our cell assembly (Fig. 1).
In order to assess the getter’s effects, a residual gas analysis
was performed on cells featuring getters and cells without
getter. The inner atmosphere of the cells was analyzed with ahigh sensitivity quadrupole mass spectrometer. The
comparison of the results exhibits the getter’s strong ability to
reduce the residual pressure of the main impurities generated
during the anodic bonding process, e.g. H2, N2, O2 and CO2[405]. In particular, the average pressure of the total impurities
in getter-integrated cells was found to be 4·10-2 mbar while itwas 2 mbar in getter-free cells, which represents a 50-foldimprovement. In addition, the pressure errors among the cells
were drastically reduced for the getter-integrated cells. The
difference in the pressure of neon was within the pressure
error range typically obtained with our neon filling technique,indicating that neon was not absorbed by the getter.

Fig. 1: Schematic ofa miniature Cs-vapor cell

Since this residual gas analysis was only performed on cesium-free cells, further investigations werecarried out by coherent population trapping spectroscopy on cells embedding a dispenser and cesium
vapor. The uniformity in neon pressures was verified, along with the quality of the cesium-neon
atmosphere.
404

M. Hasegawa et al., "Microfabrication of cesium vapor cells with buffer gas for MEMS atomic clocks", Sensors andActuators A: Physical 167.2, p 594-601, 2011.
405

S. Mack, et al. "Analysis of Bonding-Related Gas Enclosure in Micromachined Cavities Sealed by Silicon Wafer
Bonding", Journal of the Electrochemical Society 144.3, p 1106-1111, 1997.

IFCS-EFTF3-PCD3-8

Improved frequency instability of PTB’s fountain clocks
V. Gerginov, B. Lipphardt, M. Kazda, N. Nemitz, S. Weyers
Time and Frequency Department, Physikalisch-Technische Bundesanstalt, Braunschweig,
Germany
Email: Stefan.Weyers@ptb.de
Since a couple of years the PTB fountain clocks CSF1 406 and CSF2407 regularly contribute to thesteering of International Atomic Time TAI408. At the same time they are used for the realization of thetime scale UTC(PTB)409, which is the basis for legal time in Germany. Work and investigations towards
further improvements of the fountains’ systematic uncertainties and their frequency instabilities arecontinued. This is particularly important in view of the demands of optical frequency standards, which
nowadays surpass the performance of fountain clocks in terms of frequency instability and uncertainty.
The frequency instabilities of CSF1 and CSF2 contribute both to the statistical and to the systematic
uncertainties of frequency measurements. An example for the latter contribution is the collisional shiftuncertainty, which is dominated by the statistical uncertainty of its evaluation. To reduce thecontribution to the fountain frequency instability, which is caused by the Dick effect410, we set up an
optically stabilized microwave source as described in previous work411. In the new setup a dielectricresonator oscillator (DRO) is stabilized to a cavity stabilized laser which in turn is referenced either toone of the optical clock transitions of a single Yb+ ion412 or to a hydrogen maser. The DRO signal can beused by both fountains for the generation of the required clock transition signal. Recently we measured
the electric quadrupole transition frequency in a single trapped 171Yb+ ion with the fountain CSF2.
During this measurement campaign the DRO stabilized to the same optical transition was utilized,
resulting in a frequency instability improvement by a factor of 2.
The second contribution to the fountain frequency instability, which is caused by quantum projection
noise, can be reduced by increased atom numbers. For this purpose, we recently employed a cold atom
beam source for loading the optical molasses of CSF2. As a result, another factor of 2 improvement of
the frequency instability reaching <510-14(1s) was achieved when the optically stabilized DRO was
utilized at the same time.

406

S. Weyers et al., Metrologia 38, 343 (2001); S. Weyers et al., Proc. 6th SFSM, St. Andrews 2001, 64–71

407

V. Gerginov et al., Metrologia 47, 65 (2010); S. Weyers et al., Metrologia 49, 82 (2012)

408

BIPM CircularT, monthly, available at: http://www.bipm.org/jsp/en/TimeFtp.jsp

409

A. Bauch et al., Metrologia 49, 180 (2012)

410

G. J. Dick, Proc. 19th Precise Time and Time Interval (PTTI) Meeting, Redondo Beach, California, 133-147, 1988

411

B. Lipphardt et al., IEEE Transactions on Instrumentation and Measurement 58, 1258 (2009); S. Weyers et al.,Phys. Rev. A 79, 031803(R) (2009)

412

Chr. Tamm et al., Phys. Rev. A 80, 043403 (2009); N. Huntemann et al., Phys. Rev. Lett. 108, 090801 (2012)

IFCS-EFTF3-PCD3-9

NPL Rb fountain: upgrade and new frequency measurements
Yuri B. Ovchinnikov1, 2, Krzysztof Szymaniec1, Soliman Edris2
1

National Physical Laboratory, Teddington, UK
2
University College London, London, UK
Email: yuri.ovchinnikov@npl.co.uk

The NPL Rb fountain frequency standard413 wascharacterized in 2010 with a total Type B uncertainty of
3.7×10-16. The first measurement of the absolute
frequency of the ground Rb hyperfine transition in 2010
gave the value of 6834682610.904308(5.2), which
agreed well with the SYRTE measurement of 2009414.
In 2012 the minimization and characterization of the
distributed cavity phase shifts reduced the total Type B
uncertainty of the NPL Rb fountain down to 2.4×10-16.
Recently we have found that, after 8 years of operationof the Rb fountain, the background pressure of the Rb
thermal vapors in the MOT chamber and the detection
section has increased to 5×10-10 mbar. To eliminate
problems related to the presence of thermal Rb atoms,
the fountain was opened and its detection section
upgraded. An additional detection chamber with optical
viewports has been introduced at the bottom of thefountain to increase the optical access to the atoms,
which should essentially increase the efficiency of thedetection and thus the frequency stability of thefountain. In addition, the orientation of the probe
detection beams in the new setup is rotated by 45 withrespect to the feeds of the Ramsey microwave cavity. Fig. 137: Upgraded NPL Rb fountain.
This will essentially suppress the m=2 term of the
distributed cavity phase shift415.
The results of new measurements of the ground Rb hyperfine splitting in the clean and upgraded NPL
Rb fountain will be reported.

413

Y. Ovchinnikov and G. Marra, “Accurate rubidium atomic fountain frequency standard”, Metrologia, vol. 48, p. 87-100,
2011.
414

J. Guena et al, “Demonstration of a dual alkali Rb/Cs atomic fountain clock”, IEEE Trans. Ultras. Ferr. Freq. Cont., vol.
57, p. 647-53, 2010.
415

R. Li and K. Gibble, “Evaluating and minimizing distributed cavity phase errors in atomic clocks”, Metrologia, vol. 47, p.
534-51, 2010.

IFCS-EFTF3-PCD3-10

Current status of NICT atomic fountains
Motohiro Kumagai1, Clayton R. Locke1, Hiroyuki Ito1, Kohta Kido2, Nobuyasu Shiga1,2, Masatoshi
Kajita1, Yuko Hanado1 and Mizuhiko Hosokawa1
1

Space-time Standards Laboratory, National Institute of Information andCommunications Technology (NICT), Tokyo, Japan
2
PRESTO, Japan Science and Technology Agency (JST), Japan
Email: mkumagai@nict.go.jp

Atomic fountain frequency standards have been developed at NICT for contributions to thedetermination of TAI, frequency calibration of Japan standard time, and accuracy evaluation of opticalfrequency standards. The first fountain (NICT-CsF1 [1]) has been in operation since 2006 and has atypical frequency uncertainty of 1.4 x 10-15. A recent vacuum system overhaul and resulting improvement
in residual gas pressure now means it is possible to capture more atoms, leading to an improved shortterm stability of 6 x 10-14 /1/2. As before, a cryogenic sapphire oscillator is used as a reference. However,this high atomic density is associated with a large collisional shift. To reduce the uncertainty of thecollisional shift, we have installed rapid adiabatic passage method for state-selection [2]. This method
allows the number of the atoms contributing to the signal to be changed by a precise factor of 2.
Installation of rapid adiabatic passage enables both high frequency stability and accuracy. Additionally,following the new approach proposed in [3], we are currently re-evaluating the distributed cavity phase(DCP) shift in CsF1.
A recently constructed second fountain (NICT-CsF2) has now attained the goal of operation at the 10level. This second fountain is vital for inter-comparison evaluation of frequency shifts and theirassociated uncertainties with the first fountain, and also provides redundancy necessary for guaranteed
contribution to TAI. In contrast to CsF1 which uses a (0,0,1) laser cooling geometry with quadruple
magnetic field, CsF2 adopts (1,1,1) geometry enabling many atoms to be captured without a magnetic
gradient in large diameter laser beams, resulting in a reduction in the atomic density and thus a smaller
collisional shift. Moreover, large initial size of the molasses makes it insensitive to phase distribution
inside the Ramsey cavity. Currently CsF2 has a frequency stability of 3 x 10-13 /1/2 and averages down toa statistic uncertainty at the 10-16 level. We have completed evaluations of most systematic frequency
shifts and their uncertainties for CsF2 at a level below 5 x 10-16, and the remaining measurements for
microwave related shifts are currently underway.
16[1] M. Kumagai et al; “Evaluation of caesium atomic fountain NICT-CsF1” Metrologia 45, 139-148,
2009[2] Dos Santos et al; “Controlling the cold collision shift in high precision atomic interferometry” Phys.
Rev. Lett. 89, 23, 2002
[3] J. Guena et al; “Evaluation of Doppler Shifts to Improve the Accuracy of Primary Atomic Fountain
Clocks” 106 130801, 2011

IFCS-EFTF3-PCD3-11

Distributed cavity phase calculation for a rectangularRamsey cavity in NRC-FCs1
Louis Marmet1, Nicolás A. Shtin2, Pierre Dubé1, J. Mauricio López R.3
1

Measurement Science and Standards, NRC, Ottawa, Canada
2
SMK Electronica S.A. de C.V., Tijuana, México
3
Time and Frequency Division, CENAM, Queretaro, México
Email: louis.marmet@nrc-cnrc.gc.ca
We describe a numerical calculation of the contributions to the frequency shifts from the distributed
cavity phase used in the fountain clock FCs1. The Ramsey cavity is rectangular as opposed to thecylindrical cavities used in most fountain clocks. It
operates on the TM210 mode with a transversal C-field (Xaxis). The microwave signal is coupled into the Ramsey
cavity via two low-coupling magnetic antennas(rectangular loops 2.6mm × 0.5mm) through slits locatedon the sides of the cavity (Fig. 1). The cavity has a loaded
Q=4600. It is made of two identical halves held together
symmetrically about the YZ-plane.
The cutoff
waveguides have cylindrical symmetry, with a conicalshape near the cavity center in order to keep the atoms
away from the high fields at the edges and minimize phaseshifts416.
The numerical evaluation of the field in the cavity is madeusing of a full-wave finite element EM solver. Only theTM210 mode is coupled to perfectly symmetrical antennas.
A mode expansion417 is also used to evaluate thecontributions from other modes to the phase variations.
The frequency shift of the cavity is evaluated bysimulating the path of the atoms along the free-falltrajectories through the cavity while solving numericallyfor the Bloch vector with the TM210 mode. Contributions
from phase gradients and other modes are added as a
Fig. 138: Magnetic field amplitude of theperturbation to the Bloch vector solution.
TM210 mode (white: large, black: weak)in the YZ-plane through the center of thecavity. The field is in the X-direction (intothe page).

416

L. Marmet, B. Hoger, P. Dubé, A.A. Madej, J.E. Bernard, “Detailed description of FCs1: NRC’s cesium fountain primary
standard”, Proceedings of the IEEE IFCS, pp. 386-391, 2008 and references within.
417

N. Ashby, S. Römisch, S.R. Jefferts, “Endcaps for TE01 cavities in fountain frequency standards”, Proc. Frequency
Control Symposium, pp. 1076–83, 2003.

IFCS-EFTF3-PCD3-12

An atomic gravimeter at KRISS: Current status
Sang-Bum Lee1, Sang Eon Park1, Myoung-Sun Heo1, Shin Hyuk Yim2, Dai-Hyuk Yu1, Chang Yong
Park1, Won-Kyu Lee1, and Taeg Yong Kwon1
1

Korea Research Institute of Standard and Science, Daejeon 305-340, Korea
2
Agency for Defense Development, Daejeon 305-154,Korea
Email: lsbum@kriss.re.kr

Figure 1 shows a physics package for atomic gravimeter which consists of a Magnetic Optical Trap
(MOT) chamber followed by Raman interferometer and detection zone below. The MOT chamber has
1,1,1 geometric configuration with three fold symmetry cooling beams (three upward beams, threedownward beams) about vertical axis. The vacuum components were made of nonmagnetic titanium inorder to reduce the distortion of a magnetic fieldDistance from the center of the MOT chamber todetection zone is about 30cm corresponding to duration time 100 ms between the pulses in the MachZehnder-type interferometer using 22sequence of Raman pulses. The zone is composed of
two parts whose upper part and lower part are used to measure atoms of an excited state and atoms of aground state for normalizing population rate by measuring the number of total atom, respectively. We
use rubidium-87 (Alvatec, Alvasource), which can be controlled by the heating current, as an atomic
source.
We use a three home-made external cavity diode lasers (ECDL) as laser system for atomic
gravimeter418. ECDL1 is stabilized to D2 line (F=2 to F’3) using modulation transfer spectroscopy(MTS) and is used for detecting populated atom and pushing for state selection. ECDL 2 is frequencylocked to ECDL1 and is alternatively used as a repumper and a mater Raman laser by controlling thefrequency difference between the two lasers.
ECDL3 is frequency or phase-locked to ECDL2 andis alternatively used as a cooling laser and a slave
Raman laser. We have achieved the residual phasenoise below-120 dBrad2/Hz between two phaselocked lasers in the frequency range from 100 Hz to
350 kHz, which will give a limit to the sensitivity at
a level of 1x10-10g/Hz-1/2.

Fig. 139: Photograph of an atomic gravimeter
developing at KRISS.

418

P. Cheinet, F. Pereira Dos Santos, T. Petelski, J. Le Gouet, J. kim, K. T. Therkildsen,
A. Clairon, A. Landragin, “Compact laser system for atom interferometry”, Appl. Phys. B, vol. 384, p. 643-646, 2006.

IFCS-EFTF3-PCD3-13

A trapped atom interferometer for the measurement of shortrange forces
Minkang Zhou, Bruno Pelle, Adèle Hilico, Peter Wolf and Franck Pereira dos Santos
LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, LNE, Paris, France
Email: minkang.zhou@obspm.fr
I will present the status of an experiment, which aims at performing precise measurements of theinteraction forces between atoms and a macroscopic surface, for surface separations from 0.2 μm to 10
μm, where QED effects are predominant419. In our experimental apparatus, we have demonstrated laser
controlled tunneling of 87Rb atoms in a vertical optical lattice using two- photon Raman transitions420,
allowing performing high resolution laser spectroscopy of Wannier Stark (WS) states. With this shallow
optical lattice, three different kinds of trapped atom interferometers are realized by using a state-labelingtechnique with WS states: a Ramsey-type interferometer sensitive both to clock frequency and external
forces421; a symmetric accordion-type interferometer, sensitive to external forces only422; and amultiwave interferometer, insensitive to Raman and lattice light shifts. The Bloch frequency B=mg/2hhas been measured with a relative sensitivity of 9.1×10-6 at 1 s by the accordion-type interferometer.
The limits in terms of sensitivity of those schemes are analyzed.

419

P. Wolf, P. Lemonde, A. Lambrecht, S. Bize, A. Landragin and A. Clairon, Physical Review A 75, 063608, 2007.

420

Q. Beaufils, G. Tackmann, X. Wang, B. Pelle, S. Pelisson, P. Wolf and F. Pereira dos Santos, Physical Review Letters106, 213002, 2011.

421

G. Tackmann, B. Pelle, A. Hilico, Q. Beaufils and F. Pereira dos Santos, Physical Review A 84, 063422, 2011.

422

B. Pelle, A. Hilico, G. Tackmann, Q. Beaufils and F. Pereira dos Santos, Physical Review A 87, 023601,2013.

IFCS-EFTF3-PCD3-14

Large Area Cold Atom Gyroscope
M. Meunier, I. Dutta, C. Guerlin, C. Garrido Alzar, A. Landragin
LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, 61 avenue de l’Observatoire, 75014 Paris, France
Email: arnaud.landragin@obspm.fr
After demonstrating a new butterfly geometry based on a 4 pulses sequence using one Raman beam423,
we developed a new ultra large area cold atom gyroscope, allowing a 300-fold increased area, up to 11
cm2 and aiming to achieve a sensitivity in the range of 10-10 rad/s @ 1000 s. Wave-front distortions wereidentified as the main limitations to the accuracy and the long term stability on the previous
experiment424, and have been addressed. The use of one single source of atoms and a vertical trajectory
as in atomic fountains lead also to a more robust configuration. This new experiment will enable us to
explore the fundamental limits of these interferometers, demonstrating continuous rotation
measurements (at 2 Hz) for inertial sensing, or participating in new improvements in geophysics, for the
study of tilt fluctuations of the Earth rotation axis.
This new large area gyroscope is made of a 1 m high titanium vacuum chamber, surrounded by twolayers of mu-metal, protecting from the ambient magnetic field fluctuations. Cesium atoms are loaded
from a 2D MOT with a loading rate of 109 atoms/s into the 3D MOT, where the atoms are cooled down
to a temperature of about 1.2 μ K. The atoms are launched vertically at a velocity up to 5 m.s-1 thanks toa moving molasses technique. After the launch, the atoms in the level |F = 3, mF = 0> are selected inorder to reduce the sensitivity of the interferometer to parasitic magnetic fields. The number of atoms
entering the interferometer is about 2 .107.
Atomic wave packets are manipulated by Raman lasers, enabling the transition between the two
fundamental states of the Cesium atom. The Raman lasers are horizontal and applied 4 times, in a π/2-ππ_π/2 pulse sequence, to realize a folded 8 shape interferometer1, insensitive to DC acceleration. The
E
atoms in free fall are then sensitive to the Sagnac phase shift, which can be written as Dj = 2W.A 2
hcwhere A is the area of the interferometer and E the particle Energy.
The total interaction time can be adjusted by using either one pair of Raman laser for short interaction
times (below 125 ms) or two pairs of Raman laser for long interaction time (up to 800 ms). We got firstatomic fringes using two pairs of stimulated Raman lasers in the two bottom windows (480 ms), doing ainterferometer of 2.5 cm2. We achieve a sensitivity of 7.10−7 rad/s @ 1s limited by spurious vibrations.
We are now optimizing the filtering of the parasitic vibrations in order to improve the signal to noise andto benefit from the maximum interrogation time of 800 ms reachable, leading to the macroscopic area of
11 cm2.

423

B. Canuel, F. Leduc, D. Holleville, A. Gauguet, J. Fils, A. Virdis, A. Clairon, N. Dimarcq, Ch. J. Bordé, A. Landragin et
P. Bouyer, "Six-axis inertial sensor using cold-atom interferometry", Phys. Rev. Lett. 97, 010402, (2006).
424

A. Gauguet, B. Canuel, T. Lévèque, W. Chaibi, and A. Landragin, "Characterization and limits of a cold atom Sagnac
interferometer", Physical Review A 80, 063604, (2009).

IFCS-EFTF3-PCD3-15

Figure of merit and limit of short-term stability in passivehydrogen maser
Kozlov S.A., Vasilyev V.I.
Institute of Electronic Measurements KVARZ, Nizhny Novgorod, Russia
Email: nnipi_kvarz@sinn.ru
We present an investigation of frequency short-term stability of a passive hydrogen maser (PHM) bysingle frequency modulation425.
Frequency stability of any passive frequency standard is associated with the figure of merit of a quantum
discriminator (physics package), characterized by the ratio of signal/noise to the width of the atomic
transition spectral line during indicating the atomic resonance. The larger this parameter, the higher isshort-term frequency stability of the maser.
Calculations of the figure of merit of the discriminator in the PHM are carried out. The relationshipbetween the figure of merit and frequency stability of PHM is shown. The method of the discriminatorfigure of merit measuring is presented. The lowest achievable short-term frequency stability isevaluated. The experimental results of measuring the figure of merit and short-term stability of thepassive hydrogen maser are given.
For investigation of a limit of stability we studied change of the slope of discriminator curve Sd(therefore, figure of merit) at change of a excitation signal power426. The theoretical prediction of the
maximum Sd is based on the solution of the passive hydrogen maser equations in a «stеady-state»approximation.
Amplitude characteristics of the quantum hydrogendiscriminator were experimentally investigated forverification of theoretical model. The result ofc)investigation presented in Figure 1, shows that the
spectral line shape corresponds to Lorentz line shape
only at small (  90...  100 dBm) excitation signalb)power. With increase in a excitation signal power it isobserved not only broadening, but also stronga)distortion of the spectral line. The line shape can beconsidered as the sum of several spectral lines. We
explain the spectral line splitting by Stark – Zeeman
dynamic effect thatappears in strong alternating
electromagnetic fields.
Fig. 140. The PHM spectral line shape at a different
excitation signal power:

The discovered effect limits short-term stability ofa) – 94 dBm; b) – 74 dBm; c) – 67 dBm.
PHM.

425

Demidov N.A., Pastukhov A.V., Uljanov A.A. Progress in the development of IEM Kvarz passive hydrogenmasers// Proc. of the 31 Annual Precise Time and Time Interval Applications and Planning Meeting, – USA, California,
Dana Point. – 1999, pp. 579-588.
426

Kozlov S.A., Logachev V.A. Influence of the various factors on the passive hydrogen maser frequency instability//
Proc. of the 51 Annual Frequency Control Symposium. – USA, Orlando. – 1997, pp. 286-294.

IFCS-EFTF3-PCD3-16

A new laser frequency locking method based on the normal andabnormal saturated absorption spectroscopy of 87Rb
Jian Guo1,2, Jianhong Wan1, Yanhui Wang1,2
1School of Electronics Engineering and Computer Science, Institute of Quantum Electronics,
Peking University, Beijing, China
2
Department of Applied Electronic Engineering, School of Software and Microelectronics,
Peking University, Beijing, China
Email: wangyanhui@pku.edu.cn

The normal saturated absorption spectroscopy has been widely used to probe closely spaced fine andhyperfine structures of atoms and molecules with a high resolution, and also is used to lock the laser
frequency. This kind of locking method is already accepted and used by many groups to do someresearch work in the application of high precision measurements, cold atoms experiments and atomic
frequency standards. However, due to the “many peaks” of the saturated absorption spectrums, wrong
locking position phenomenon can happen sometimes. And the system is fragile for some kind ofvibrations. These restrict the further applications of the traditional locking method.
The abnormal saturated absorption spectrum was found more than 30 years ago. By changing thepolarization and the optical power, reversed peak of saturated absorption spectra can be observed.
In our experiment, we first obtained the normal and abnormal saturated absorption spectrums of 87Rb
simultaneously. With the help of the electronic circuits, these two signals are subtracted and only “onemain peak” spectrum is left, which is shown in fig.1. This new spectrum is the reference for one diodelaser frequency locking. After more than one month measurement, we find that the new system is quite
insensitive for the sudden vibrations and also can avoid the wrong locking. The long-term locking
performance of the diode laser is improved.

Normalized Signal(V)1.5

Subtraction of two Doppler-free saturated
87
absorption spectrums of Rb
1.0

0.5

0.0

Scan laser frequency
Fig.1. The subtraction of two Doppler free saturated absorption spectrum of 87Rb

IFCS-EFTF3-PCD3-17

Electron Spin Resonance Spectroscopy of Macroscopic Crystals
Warrick Farr,1 Karim Benmessai,1 Daniel L. Creedon,1 Yarema Reshitnyk,2 Nitin Nand,1 Maxim
Goryachev,1 Jean-Michel Le Floch,1 Timothy Duty,3 and Michael E. Tobar1
1

ARC Centre of Excellence for Engineered Quantum Systems,
University of Western Australia, Crawley WA 6009, Australia
2
ARC Centre of Excellence for Engineered Quantum Systems,
University of Queensland, St Lucia QLD 4067, Australia
3
ARC Centre of Excellence for Engineered Quantum Systems,
University of New South Wales, Sydney NSW 2052 , Australia
Email: farrw01@student.uwa.edu.au
The development of a new era of quantum
devices requires an understanding of how
paramagnetic dopants or impurity spins
behave in crystal hosts. In the most recent
experiment HEMEX grade sapphire used as aClassical Cryogenic Sapphire or a maser
oscillator in the range 10-40 GHz, specificions, such as the Fe3+ ion are at the heart ofpoorly understood, phenomena [1]. The ion
parameters, the active ions concentrations,
their spin-spin and, spin-lattice relaxation
times are not well known in our crystals andneed to be characterized.

Fig. 141: The transmission of a Whispering Gallery(WG) mode doublet at 13.868 GHz, interacting with
Electron Spin Resonance (ESR) packets of ion
impurities under the influence of a DC magnetic
field.

We present a new spectroscopic technique which uses traditional Electron Spin Resonance (ESR)
combined with the measurement of a large population of high Q factor electromagnetic Whispering
Gallery (WG) modes.
Measurements of high purity sapphire and rutile crystals cooled close to 20 mK in temperature, are used
to identify and determine the concentration of trace paramagnetic ions, their sensitivity to a DC
magnetic field, and the width of such ions. Our measurement is different to ESR in that it is possible to
track the resonant frequency of the ions over a wide range of negative and positive magnetic fields up to± 10 kG, allowing excellent measurement of the AC magnetic susceptibility. This high precision reveals
anisotropic behavior of the Zeeman splitting. In our sapphire crystals, we observe a different g-factor forthe two Zeeman components of the |±3/2〉to |±1/2〉transition in the Fe3+ ion.
[1] Creedon, D.L.; Benmessai, K.; Tobar, M.E.; Hartnett, J.G.; Bourgeois, P.-Y.; Kersale, Y.; le Floch,
J.-M.; Giordano, V.; , "High-power solid-state sapphire whispering gallery mode maser," Ultrasonics,
Ferroelectrics and Frequency Control, IEEE Transactions on , vol.57, no.3, pp.641-646, March 2010,
doi: 10.1109/TUFFC.2010.1460

IFCS-EFTF Group 4 poster session 2
Forum Hall
Wednesday & Thursday, July 24-25, 2013, 1:00 pm - 2:00 pm and 3:30 pm - 4:30 pm
Chair:

Fabien Josse
Marquette University

IFCS-EFTF4-PCD4-1

A stroboscopic approach to surface acoustic wave delay lines
interrogation
Chrétien N.1, Friedt J.-M.1, Ballandras S.1,2, Martin G.2
1

2

SENSeOR, Besançon, France
Time & Frequency, Femto-ST, Besançon, France
Email: nicolas.chretien@femto-st.fr

Acoustic delay lines are well known transducers used as passive sensors interrogated through awireless link. Multiple electronic reader units have been presented in the literature, most of which are
based on the FMCW RADAR approach whose control of the spectrum use and radiofrequency synthesis
circuit is most basic, although requiring significant computational power (periodic audio-frequency rate
sampling and Fourier transform) to extract the electrical properties of the acoustic delay line acting ascooperative target. Furthermore, FMCW requires a well linearized voltage controlled oscillator or linear
digital synthesis for the Fourier transform components to coherently sum throughout the frequency
excursion over the transfer function of the transducer.
Here, we assess the use of a pulsed RADAR approach in which the instantaneous power reaching
the target is greatly increased, even though the average power consumption (depending on pulse
repetition rate) is of the same order of magnitude than those found in FMCW. A carrier frequency
generated by various sources (868 or 2450 MHz center frequency, 30 to 80 MHz bandwidth) withdifferent phase noise stabilities is chopped by a fast (< 30 ns rise time) switch to load energy in an
acoustic delay line. In order to comply with the requirements of compact, low power receiverelectronics, a stroboscopic equivalent time sampling approach is demonstrated. The two values
representative of the physical quantity detection by the transducer are the returned power magnitude andphase, as provided by an I/Q demodulator.
This demodulator provides an output signal of 20 MHz to 100 MHz bandwidth which involves
digitizing a signal at 200-1000 MSamples/s to obtain a sufficient number of points to extract magnitude
and phase with the targeted resolution aimed at only being limited by the local oscillator phase noise.
The equivalent-time sampling approach provides a trade-off between reducing the demand for fastelectronics components and increasing the acquisition time.
A strategy for generating high resolution time delays (Δτ =250 ps for an equivalent sampling rateof 4 GS/s) while allowing for long interrogation durations (up to 5 microseconds) is implemented by
combining an FPGA-based delay generator with commercially available delay lines. The measurement
sequence of generating interleaved combs is due to the long delay line reconfiguration duration (SPI
communication) with respect to the coarse comb (FPGA based counter). I and Q components arerecorded and processed to acquire the coarse acoustic velocity information through magnitude
measurement, and an accurate physical quantity estimate is computed thanks to the phase information.
Using this strategy, the optimum recording duration of 100 ms for sampling 20000 points (20000 points
x 5 µs/point = 100 ms) is achieved with a sufficient resolution for identifying an 8-bit code.

IFCS-EFTF4-PCD4-2

SAW sensor exploiting palladium layer properties for selective
detection of hydrogen
Vanotti Meddy1, Rauch Jean-Yves2, Ballandras Sylvain3, Blondeau-Patissier Virginie1
1Time and Frequency Department, Femto-st Institut, Besançon, France
2
Department of Optics, Femto-st Institut, Besançon, France
3
Freq'N'sys, Besançon, France
Email: meddy.vanotti@femto-st.fr

For an increasing number of applications, hydrogen represents a solution for the future. However, due toits unstable properties, a particular care must be dedicated to control any leakage. In previous works, it
has been shown that surface acoustic wave (SAW)
sensors functionalized with a thin PVD palladium
layer allow for detecting gaseous hydrogen427.
Here we propose a study of different sensitive
layer (thickness and composition) for thesedetections. It has been shown428 that the two main
parameters that influence the phase velocitychange of elastic waves are mass- and elasticloading.
First it can be seen in Fig. 1 that our device
functionalized with a 300nm palladium overlay Fig. 1: Phase shift due to hydrogen absorption in aenables for the detection of hydrogen in standard palladium layer which thickness is 300nm
conditions. Such a detection is made by exploiting (performed at atmospheric pressure in air).
elastic-loading. Indeed, changes of elastics
properties of the palladium layer consecutive to thehydrogenation2 induce an increase of the phasevelocity.
Secondly, as shown in Fig. 2, hydrogen absorptionina thin palladium layer (15nm) deposited onto thesame type of delay line induces totally different
observations. Indeed for such an overlay, the main
phenomenon that is observed is no more elasticloading but mass-loading.
Finally, as an Yttrium doping of the palladium
layer is expected to provide improvement on the Fig. 2: Phase shift due to hydrogen absorption in a
detection429, part of this study is also dedicated to palladium sensitive layer which thickness is 15nm its(performed at atmospheric pressure in nitrogen).
benefits.
427

M. Vanotti and al, “Selective Detection of Hydrogen with Surface Acoustic Wave Devices Using Palladium Layer
Properties”, Sensors and Transducers, vol. 14-1 special, pp. 197 – 211, 2012.
428
V. Anisimkin and al, “Elastic properties of thin-film palladium for surface acoustic wave (SAW) sensors”, Sensors andActuators B: Chemical, vol. 23, no. 23, pp. 203 – 208, 1995.
429
L. Yia and al, “Hydrogen gas sensor based on palladium and yttrium alloy ultrathin ﬁlm”, Review of scientificinstruments, vol. 83, 2012.

IFCS-EFTF4-PCD4-3

Large capacity SAW tag
Xin Huang1, Zhijun Chen1, Hailin Xu2, Mengyang Wang1, Ruan Peng1, Peidi Chen2
1
College of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing,
China,
2
China Electronics Technology Group Corporation No.55 Research Institute, Nanjing, China
Email: huangxin931@126.com
The research on SAW tag has lasted many years. However, the application and promotion are unsatisfactory
due to the inherent defects of the manufacturing technology of large capacity SAW tag. In order to ensure theconsistent amplitude of reflector echoes and time domain resolution sensitivity, tags with different codesneed to be designed and manufactured separately, leading to high manufacturing cost. This paper proposes a
new method using anti-collision tag units to form a combined tag so as to expand the capacity of SAW tag
and reduce the cost.
The key of an anti-collision SAW tag unit is the coding IDT. By using barker code sequence or Orthogonal
Frequency Coding (OFC) method etc., the coding IDT obtains coding and anti-collision characteristics. The
output of coding IDT achieves the maximum peak value, which is defined as autocorrelation, only if the codeof the input pulse is the same as the code of IDT. For example, Fig.1 shows the simulation result of thecoding IDT output when 7-bit barker code sequence [1110010] is used, wherein Fig. 1(a) shows the
autocorrelation. Fig. 1(b) is the output when input sequence is [1011000], which is the minimum crosscorrelation peak value between 7-bit barker codes.
The structure of the tag unit is shown in Fig.2,
including a coding IDT and a number ofreflectors. With the anti-collision characteristicof coding IDT, each tag unit responds to a
specific code modulation carrier pulse. Whenreader sends a sequence of different inquiry
code modulation carrier pulses, the tag units
with corresponding codes respond one by one
according to the order of the inquire pulses. The(a)7-bit barker code(b)[1011000] withconsistency degree N, determined by the[1110010]
method used in the coding IDT, is the number
autocorrelation
crossof tag units in a combined tag. Thus, a highconsistency degree of non-periodic polar code correlation
142: The
CodeFig.Code
Code output of coding IDTgroup is necessary in large capacity applications. Our sequence
N sequence 2 sequence 1
group recently has found a 13-bit encoding groupbased on the communications coding theory, theconsistency degree of which reaches 8. If the number
Coding IDT 1
Code ATag unit 1
Code A Code B Code X
of reflectors in each unit is 10, the capacity of this tag
Coding IDT 2
Code B
is 1.2*10^24 (1024^8=1.2*10^24), which is enoughTag unit
Tag unit 2
for most applications. While under the same1 1 01011010
Coding IDT N
Code X
circumstance, the capacity of a traditional SAW tag is
Tag unit N
CombinedTag
only 1024*8.
Fig. 2: The structure of tag unit and combined tag
This paper proposes a novel SAW tag consisting ofseveral anti-collision tag units and combining code
division and time division. By means of such novel SAW tag, a new low-cost and universal RFID system
can be formed, which facilitates the implementation of large capacity SAW tags and multifunctional SAW
wireless sensors.
Coding IDT

Reflectors

IFCS-EFTF4-PCD4-4

A micro-machined Tonpilz hydrophone
for audible frequency sounds
Min Sung1, Hak Sue Lee2, Won Kyu Moon1
1

Dept. of Mechanical Engineering, Pohang Univ. of Science and Technology(POSTECH),
Pohang, Kyungbuk/Republic of Korea
2
Agency for Defense Development, Changwon, Kyungnam/ Republic of Korea
Email: wkmoon@postech.ac.kr

Micro-machined underwater acoustic sensors have been studied because of their many advantages
including small size and low-cost by batch-fabrication430-431. But the sensitivity is not good enough at
the low audible frequency such at 100 Hz for use in SONAR. In this study, a micro-machined Tonpilz
hydrophone based on the piezoelectric thickness mode was designed for the audible frequency range 20
Hz ~ 20 kHz. The basic structure of the sensor was motivated by the structure of conventional Tonpilz
transducers, but two different design approaches were adopted to enhance sensitivity and to endure thehigh underwater hydrostatic pressure. For improved sensitivity, the area ratio of the head-mass and thepiezoelectric body was designed to be several hundreds to one, which amplifies the input of thetransduction body due to acoustic pressure. Since this approach is adopted in order to develop aminiaturized hydrophone manufactured by batch processing, the size of the piezoelectric transduction
body becomes too small to generate a sufficient amount of charge for using the conventional preamplifier for signal detection at low frequencies below 500 Hz. For endurance to the hydrostaticpressure in deep-water, the proposed structure needs oil backing for balancing the hydrostatic pressure
from the environment on the front surface ofsensing membrane as can be seen in Fig. 1.432
We have developed a lumped parameter model
to identify the requirements for the pre-amplifier
circuits and the available sensitivity at low
frequencies and to search for the appropriate
design for miniaturized hydrophones. The
designed hydrophone was then fabricated by
micromachining. The eutectic bonding technique Fig. 143: Concept of the proposed micro-machined
was used to combine the pressure amplification Tonpilz hydrophone (circular shape in top view)structure and the patterned PZT. The fabricateddevice was packaged with the custom-made pre-amplifier inside the castor oil-filled rubber housing. The
constructed hydrophone was tested using the commercial hydrophone in a small anechoic bath toconfirm the feasibility to be used as an effective micro-size underwater sound receiver.

430

J. Bernstein, "A micromachined condenser hydrophone," in Digest IEEE Solid-State Sensor and Actuator Workshop, pp. 161–165, 1992
J. Bernstein et al., "Micro-machined high frequency ferroelectric sonar transducers," IEEE Trans. Ultrason. Ferroelectr. Freq. Control
44, pp. 960–969, 1997
432
T. D. Sullivan and J. M. Powers, "Piezoelectric polymer flexural disk hydrophone," J. Acoust. Soc. Am. 63, 1396–1401, 1978
431

IFCS-EFTF4-PCD4-5

Characterization of Parylene-C Using Quartz Thickness Shear
Mode (TSM) Resonators
Huiyan Wu, Hongfei Zu, Qing-Ming Wang
Department of Mechanical Engineering & Materials Science, University of Pittsburgh,
Pittsburgh, Pennsylvania, USA
Email: qiw4@pitt.edu
Shear-Horizontal Surface Acoustic Wave Devices(SH-SAW, Love Mode) are promising in
fundamental biology as well as biomedical
engineering, detecting behaviors of cells on theirsurface in a non-invasive, simple and quantitative
manner1. Parylene-C, deposited on SH-SAW
devices’ surface, plays an important role as bothaneffective
wave-guiding
layer
and
biocompatible interfacial layer. In order toestablish reliable theoretical analysis for SH-SAW
device, however, complex shear modulus of
Parylene-C is required first. As a result, due to its
high sensitivity, repeatability and easy connection
with electrical measurement systems1, quartz Fig. 144: Admittance Magnitude Y near
thickness-shear-mode (TSM) resonator is adopted fundamental resonance of the TSM resonator withto characterize the mechanical properties of Parylene-C coatings of different thicknesses. Inset is
Parylene-C coating. Nevertheless, some problems Resonance Frequency Shift and Quality Factor of Y
of coating property extraction in TSM resonator curve for different Parylene-C coatings.
applications have not been solved completely,
including approximately-theoretical measurement and calculation error control. It has been found thatviscous coatings of various thicknesses could induce other resonance modes2, leading to incompatible
with calculation model. Therefore, in this study, Parylene-C films of different thicknesses were
deposited on the surface of AT-cut quartz TSM resonators with Au electrodes on both sides. Admittancespectra of these uncoated and coated resonators were measured by an impedance analyzer.
Correspondingly, electrical admittance of coated TSM resonators was derived based on TransmissionLine-Matrix Model (TLM), which is also widely used in SH-SAW devices. Resonance frequency shift
Δf and quality factor Q for TSM resonators with different-thickness Parylene-C coatings were obtained
from admittance spectra as shown in Fig. 1. Results indicated that the ideal thickness range for TLM
model is from 1.3 μm to 2.5 μm, and the extracted complex shear modulus of Parylene-C appeared to beuniform in this range through curve-fitting analysis. The storage modulus and loss modulus of ParyleneC are 798 MPa and 54 MPa, respectively.

1

D. S. Ballantine, R. M. White, S. I. Martin, A. J. Ricco, E. T. Zellers, G. C. Frye, and H. Wohltjen, “Acoustic Wave Sensor:
Theory, Design, and Physico-Chemical Applications”, Academic Press.
2

S. J. Martin, H. L. Bandey, R. W. Cernosek, A. R. Hillman, and M. J. Brown,“Equivalent-circuit model for the thicknessshear mode resonator with a viscoelastic film near film resonance”, Anal. Chem., vol.72, p.141-149, 2000.

IFCS-EFTF4-PCD4-6

A SH-APM liquid viscosity sensor based on PZT-5H
Zhijun Chen1, Mengyang Wang1, Jingyong Liu2, Peng Ruan1, Xin Huang1
College of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China
No.55 Research Institute, China Electronics Technology Group Corporation, Nanjing, China
Email: zjchen76@sina.com

Compared with SAW (surface acoustic wave) device, the APM (acoustic plate mode wave) device
has two interfaces. When one interface is deposited with IDTs as acoustic excitation, the other interface
can be loaded with liquid sample. Furthermore, when the APM has only SH (shear-horizontal) particle
displacement normal to the propagation direction and parallel to the plate surface, the attenuation
because of the liquid sample is very small. So the SH-APM device is applicable for liquid sensing.
Because of the variety of liquid’s characteristic parameters and the complexity of APM’s propagation
characteristics, the researches on APM liquid sensing mainly focus on non-viscous liquid. In fact, themeasurement of liquid viscosity is required and important in many applications.
In this paper, according to the material symmetry character, the excitation mechanism of SH-APM
on the basis of material constants is derived. The liquid viscosity is introduced by adding the imaginary
part in liquid elastic tensor, and the theoretical model of SH-APM device loaded with viscous liquid isbuilt using the propagation characteristics of acoustic wave in layered mediums. The liquid volume
elastic modulus doesn’t affect the propagation velocity and attenuation of SH-APM because of its SH
particle displacement. When the electrical boundary condition is free at the plate interface deposited
with IDTs and metalized at the other interface loaded with liquid, only the liquid’s density and viscosity
influence SH-APM’s propagation characteristics.
The influences of liquid density ρL and viscosity ηL on propagation velocity v and attenuation γ of
SH-APM are numerically analyzed. v and γ of SH-APM have linear relation with the square root of ρLand ηL. The velocity v decreases with the increases of ρL and ηL. On the contrary, the attenuation γ
increases with the increases of ρL and ηL. The changes of v and γ because of ηL are much larger thanthose because of ρL. It could be approximated that the changes of v and γ result mainly from liquid
viscosity ηL, and the SH-APM device could be utilized as liquid viscosity sensor. The changes of SHAPM sensitivity to liquid viscosity with the ratio of the plate thickness to the acoustic wavelength are
numerically analyzed, and the optimization design of the SH-APM device is implemented.
Using PZT-5H piezoelectric ceramic as substrate material, the SH-APM device is fabricated. The
encapsulation and photo of the SH-APM device are shown in Fig. 1. Using different ratios of pure waterand glycerol as the liquid samples, the experimental results are in agreement with the theoreticalanalyses. When the device is used as liquid viscosity sensing, not more than one milliliter liquid samples
are needed, satisfying the requirement of minim liquid measurement. The superiority of the ceramicmaterial PZT-5H used as SH-APM liquid sensing is testified.
liquidaluminium Shelladhesive
substratelead

RF connector
insulated padbottom coverFig. 1The encapsulation and photo of the SH-APM device

IFCS-EFTF4-PCD4-7

Absolute control of the scale factor in the GP2 laser gyroscope:
toward a ground based detector of the Lense-Thirring effectJ. Belfi1, N. Beverini1,2 , M. Calamai1, G. Carelli1,2, D. Cuccato3,4, A. Di Virgilio2, E. Maccioni1,2, A.
Ortolan3 and R. Santagata2,51

Dept. of Physics, University of Pisa, Largo Bruno Pontecorvo 3, Pisa, Italy
2
INFN Section of Pisa, Largo Bruno Pontecorvo 3, Pisa, Italy
3
Dept. of Information Engineering, University of Padova, Via Gradenigo 6/B, Padova, Italy
4
INFN National Laboratories of Legnaro, Viale dell'Università 2, Legnaro, Padova, Italy
5
Dept. of Physics, University of Siena, Via Roma 56, Siena, Italy
Email: beverini@df.unipi.it
Laser gyroscopes measure the angular velocity of a ring cavity with respect to an inertial frame byreading the beat frequency between the counter-propagating laser beams (Sagnac effect). GP2 is a newring laser gyroscope with the side length of 1.65 m, engineered to be the building block of a larger
triaxial detector of the frame-dragging (Lense-Thirring effect) induced by the Earth rotation on groundbased laboratory. To reach this goal, an accuracy better than 10-9 on the Earth angular velocity isrequired. The Sagnac frequency is related to the rotational speed of the gyroscope reference frame
A×cosqthrough a geometrical scale factor S =,P
where P is the cavity optical length, A the area
enclosed by the beam path, and q is the angle
between the Earth rotation axis and the area
vector. In a cavity where 4 identical sphericalmirrors are placed in ”perfect square” geometry,the sensitivity of S to the geometricalinaccuracy can be minimized, by stabilizing toan identical value the absolute length of the two
Fabry-Pérot linear resonators along the squarediagonal (Fig. 1). This control scheme will betested in GP2 experimental setup, equipped Fig. 1: Calculated scale-factor relative variation
with tridimensional PZT control system of the due to cavity misalignment. The displacement of
mirrors positions. We will present a simulation one cavity mirror from the ideal position isof the control automated system, and the considered: a) diagonal shift; b) shift out of theexperimental results on the stabilization of the plane; c) tangential shift.
absolute length of two identical linear cavities
to a He-Ne I2 frequency standard.

IFCS-EFTF4-PCD4-8

A heterodyne frequency-stabilization method for large ring laser
gyroscopes with sub-nW output power
Fabio Stefani1, Jacopo Belfi2, Enrico Maccioni2
1

Laboratoire de Physique des Lasers (LPL), Paris 13 University, Villetaneuse, France
2
Physics Department, University of Pisa, Pisa, Italy
Email: fabio.stefani@univ-paris13.fr

He-Ne ring lasers with cavity dimensions larger than 1 m can operate as ultra stable rotation rate
sensors. For such systems, the two opposite beams generated inside the cavity are frequency split
because of the Sagnac effect. The information about the rotation rate of the cavity is encoded in the
optical beat between the counter propagating beams. In order to reduce the mutual coupling between thetwo opposite beams, a high Q-factor of the optical resonator is required and no intracavity elements canbe used to select single mode operation. This implies, in general, a very low output power down to thelevel of some hundreeds pW. Such a low power and the large acoustic phase jitter make the extractionof a clean measurement of the optical frequency of the gyroscope a not trivial operation.
We will present the characteristics and the performances of a heterodyne detection scheme (see theblock scheme in the figure) allowing a robust frequency lock of the G-Pisa433 ring laser to a He-Ne-I2
reference laser. The system demonstrated a continuous unattended control of the laser frequency forseveral days of operation of the gyroscope with a single mode output power of about 500 pW.

433

J. Belfi, N. Beverini, F. Bosi, G. Carelli, A. Di Virgilio, E. Maccioni, A. Ortolan, F. Stefani, "A 1.82 m2 ring laser
gyroscope for nano-rotational motion sensing", Appl. Phys. B, 106, 271–281 (2012).

IFCS-EFTF4-PCD4-9

Finite Element Simulation of Piezoelectric Ultrasonic Devices with
Elements from Porous Piezoceramics
Andrey Nasedkin1, Maria Shevtsova 2
1
2

Department of Mathematical Modeling, Southern Federal University, Rostov on Don, Russia
Department of Mech., Phys. & Nanotechn., Southern Center of RAS, Rostov-on-Don, Russia
Email: nasedkin@math.sfedu.ru

Porous piezoceramic materials have received considerable attention due to their application in ultrasonictransducers, hydrophones and other piezoelectric devices. Porous piezoceramics has ultra high volume
piezosensitivity, expanded passband of frequencies and lower impedance than the dense ceramics,
giving a better acoustic agreement between piezoelectric and acoustic media. On the other hand its
thickness piezoelectric module remains almost the same as for the dense ceramics.
In this work the methodology of the computer modeling for piezoelectric ultrasonic devices drom porous
piezoceramics consists in the following steps. For determination of effective moduli of 3-0 and 3-3
porous piezocomposites we use an approach based on the effective moduli methods, and by the finite
element (FE) modelling of representative volumes for porous piezoceramics. FE models of high-porous
ceramics assuming the heterogeneity of the polarization vector for a variety of piezoelectric finite
elements were developed.
For determination of the effective moduli the sets of the static piezoelectric problems were determined
for representative volumes with boundary conditions, which guarantee the constant values of electric
displacements, strains, stresses and electric fields for homogeneous material. The finite element
computations were implemented using ANSYS. At that, the generation of the range of the structures forrepresentative volumes were carried out using separate programs in C++ developed by Remizov V. andsubsequent transfer to ANSYS. To take into account the heterogeneity of polarization field theelectrostatic problem for a dielectric composite was firstly solved, and the electric field that identifies
the polarization field was determined. As a result we had a representative volume of piezocomposite
with inhomogeneous properties of piezoelectric matrix (generally near the pores).
Finally the effective moduli for different types of porous piezoceramics were defined. A comparison of
the calculated basic characteristics for porous piezocomposites with the experimental data obtained at
the Research Institute of Physics, (Southern Federal University), was carried out.
We investigate 1-3 piezocomposite (piezoelectric generator), hydro-acoustic emitters made of solid
ceramics with intermediate interjacent non-piezoelectric layers and piezoelectric emitter from porous
piezoceramics without such layers. From the FE solutions of static and dynamic problems we canconclude that high porous piezoceramics is very effective material for quasistatic and low-frequency
applications in piezogenerators, since its piezo-sensitivity rapidly increases on the porosity growth. We
also note that porous ceramics is preferred for different hydro acoustic ultrasonic applications.

IFCS-EFTF Group 5 poster session 2
Forum Hall
Wednesday & Thursday, July 24-25, 2013, 1:00 pm - 2:00 pm and 3:30 pm - 4:30 pm
Chair:

Wolfgang Schaefer
TimeTech GmbH

IFCS-EFTF5-PCD5-1

High stability composite clock performances
Vernotte François1, Plantard Cedric2, Mbaye Papa Mamadou3
1

UTINAM, THETA Observatory/University of Franche-Comté & CNRS, Besançon, France
2
ESTEC, ESA, Noordwijk, Netherlands
3
ATOS, Paris, France
Email: francois.vernotte@obs-besancon.fr

The composite clock architecture we explored is composed of a VCO controlled by both a hydrogenmaser and a cesium standard. We realized two composite clock prototypes: an industrial one (passive
maser + commercial cesium) and another one suitable for metrological laboratories (active maser + highstability cesium).
This paper will describe the performances of both systems, from 0.01 s to 10 days. It will focus on the
optimizations of the system parameters for achieving the ultimate performances of this type of device,i.e. the stability of the best reference for a given integration time.
As a conclusion, we will give the development potential of this type of composite clock and some
applications.

IFCS-EFTF5-PCD5-2

Research on timescale algorithms in Database for TA(PL)Michał Marszalec1, Albin Czubla2, Włodzimierz Lewandowski3, Marzenna Lusawa4
1

Central Chamber for Telecommunications Measurements, National Institute of Telecommunications,Warsaw/Poland
2
Electricity Department, Central Office of Measures, Warsaw/ Poland
3
Time Department, International Bureau of Weights and Measures, Sevres
4
Central Chamber for Telecommunications Measurements, National Institute of Telecommunications,Warsaw/Poland
Email: M.Marszalec@itl.waw.pl
The group of Polish Time Laboratories has been cooperating closely from at least 15 years. From very
beginning also Lithuania was participating in this group. The first common initiative was organizing
independent Polish Atomic Timescale TA(PL)434. In 2004 has started a project to develop Database for
Polish Atomic Timescale TA(PL)435 to automate the process of time-standards comparison and calculate
implemented group timescale ensembles algorithms (weighted average algorithm for a group of timestandards).
Ensemble algorithms are supposed to be more stable than any of the standard within the group. This
very useful feature makes an ensemble a very good stable reference to control and supervise behavior of
every standard. In the future it could be also used to steer Polish official realization of international
Universal Coordinated Time (UTC) the UTC(PL) maintained by Central Office of Measurement(GUM). The set of ensemble algorithms was primary implemented in Database: original algorithm ofTA(PL) based on ALGOS (algorithm developed by International Bureau of Measurements –BIPM436),
one day-shifted ALGOS version and AT1(algorithm developed by National Institute of Standard andTechnology -NIST).
During last years the Time-team of Institute of Telecommunications has implemented in Database a
realization of AT2 algorithm developed on the basis of theorem published by NIST. Preliminary resultsshows that AT2 is more stable than others.
The last part of article shows analysis of results of new implemented algorithms and comparison toformer implementations.

434

J. Azoubib, J. Nawrocki, and W. Lewandowski, “Independent atomic time scale in Poland –organization andresults”, Metrologia, vol. 40, p.245-248, 2003.
435

M. Marszalec, A. Czubla and D. Nerkowski, “DataBase for TA(PL) and UTC(PL),”, Proceedings of the 40th
Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting, p. 680-690, 2008.
436

2006.

W. Lewandowski, “International Atomic Time Scales and Related Time Transfer”, special issue of MAPAN-JMSI,IFCS-EFTF5-PCD5-3

Iterative Method for Signal Path Delay Difference Estimation of
Two-way Satellite Time and Frequency Transfer
Wenke Yang1, Jianwei Zhan1, Hang Gong1, Xiangwei Zhu1, Guangfu Sun1,
1

School of Electronic Science and Engineering, National University of Defense Technology, Changsha,
Hunan 410073, China

Email: ywk@nudt.edu.cn
There are several causes of non-reciprocity in Two-way Satellite Time and Frequency Transfer(TWSTFT), including Sagnac correction, ionospheric correction, tropospheric correction, earth station
delay difference and signal path delay difference due to satellite motion in an earth-fixed frame. In
previous studies, the ranging data between the ground station and geostationary satellite should be used
to estimate signal path delay difference. In BeiDou Navigation System, TWSTFT via navigation
geostationary satellite is implemented. The broadcast ephemeris is available for Geostationary Earth
Orbit (GEO) satellite in BeiDou Navigation System, which gives a chance for a new method called
iterative method to estimate signal path delay difference.
The positions of GEO satellite when it transmits signals for two-way links are important for signal path
difference estimation. The iterative method is a way to estimate these GEO satellite positions when thereceiving epoch is known and the broadcast ephemeris is available. The proposed iterative method
works as follows. Step 1: to estimate an initial signal transfer delay from GEO satellite to the receiving
ground station. Step 2: to estimate the epoch when GEO satellite transmits signal with the receiving
epoch subtracted by the initial signal path delay. Step 3: to estimate the GEO satellite position at thetransmitting epoch with the broadcast ephemeris. Step 4: to estimate the signal transfer delay between
the estimated GEO satellite position and the position of ground station receiving signal. Step 5: to repeat
from Step 1 to Step 4 using the updated estimated signal transfer delay as the initial signal transfer delay
in Step 1, until the error between the adjacent estimated signal path delays is below the defined
threshold. Then, the GEO satellite position at the transmitting epoch for two-way links can be estimated.
Finally, signal path delay difference between two ground stations via GEO satellite can be obtained by
the difference of geometry distances of two-way links after Sagnac correction.
The TWSTFT experiment data for one day with BeiDou GEO satellite at 140°E experiment between
Beijing and Sanya has been analyzed. The signal path delay difference is estimated using ranging data
and the iterative method respectively. The experiment results show that the signal path delay differenceis about 0.115ns and the difference of the results using these two methods is less than 0.2ps. Thisimplies that there is no need to conduct ranging when the broadcast ephemeris is available for theestimation signal path delay difference.

IFCS-EFTF5-PCD5-4

Study and Application of Real-Time Frequency Deviation
Adjustment Algorithm in Establishing a Time Scale
Yiwei Wu1, Lei Chen1, Xiangwei Zhu1, Gang Ou1
1

Satellite Navigation R&D Center, School of Electronic Science and Engineering,
National University of Defense Technology, Changsha, China
Email: Yiwei_Wu_sh@126.com

Satellite navigation system is essentially a time synchronization system. It is necessary to establish astable time scale of satellite navigation system. The time scale algorithm is the key of the establishmentof a time scale. Since satellite navigation system needs real-time forecasting the state of onboard atomic
clocks, the time scale should be real-time and predictive. For high-precision positioning and timing, therequirement for the short-term stability of the time scale is relatively high.
There are a large number of papers focusing on time scale algorithms. Based on these studies andanalyses, this paper proposes a real-time frequency deviation adjustment algorithm. The main steps ofthis algorithm are follows. Firstly, use a Kalman filter to estimate the time deviation, the frequency
deviation and the frequency drift between the master clock and another clock. Secondly, adjust thefrequency deviation and predict the next time
deviation between these two clocks and thus
reconstruct the time deviation sequence.
-6

-3.38

Time Deviation

x 10

-3.39

This paper proves that the Kalman filter caneffectively filters out amounts of the white phasenoise as well as the measurement noise, the whitefrequency noise and the walk random frequency noisefrom the time deviation, the frequency deviation andthe frequency drift respectively. The simulate results
indicate that the amount of the white frequency noiseof this time deviation sequence is decreased and thestability of this time deviation sequence is improved Fig. 145: The original clock difference and theeffectively. Since the time deviation sequence is the adjusted clock difference.
adjusted clock difference between the master clock
and the other clock, conclusion can be got that thestability of the master clock’s time scale is also
improved effectively.
Time Deviation （ s）

-3.4

-3.41
-3.42
-3.43
-3.44
-3.45
-3.46

-3.47
5.554

Original Clock Difference
Adjusted Clock Difference

5.556

5.558

5.56 5.562 5.564 5.566
Time （ Julian date）

5.568

5.57

5.572
4

x 10

Allan Deviation

-12

10

-13

This paper gives the propositional implementation.
The algorithm is real-time, and its implementation iswith low cost and easy to realize and control, so thealgorithm is of high engineering and application
values.

Log（ sigma（ tao） ）

10

-14

10

-15

10

Original Clock Difference
Adjusted Clock Difference

-16

10

3

10

4

10

5

10
Log（ tao）

6

10

7

10

Fig. 2: The Allan Deviations of the original clock
difference and the adjusted clock difference.

IFCS-EFTF5-PCD5-5

An Adaptive Filtering Algorithm
With Packet Delay Variation
For IEEE 1588 Servo System
ChenLei1, ZhuTianlin2
1

2

9th Lab, BITTT, BEIJING, CHINA
Science and Technology Section, BITTT, BEIJING, CHINA
Email: chenlei0831@126.com

IEEE 1588 is a protocol for precision timing via packet networks. In the protocol, servo system in theslave will output an adjustment signal according to the calculated offset between master and slave, toachieve the goal of synchronization. Traditional IEEE 1588 servo system will be inactive after it entries
the stability state, which is caused by packet delay filtering. And unfortunately most now networks do
not support PTP(IEEE 1588, Precision Time Protocol), so the delay will be changed when routing or
waiting. For these networks in which packet delay maybe variable, traditional filtering in servo systemcannot follow packet delay variation for its inertia, and this limits the application of protocol.
To make a contribution for solving the problem that how to apply the protocol in existing networks
without mass alteration, this paper puts forward an adaptive filtering algorithm based on IEEE 1588
servo system, which can make system both filter out high-frequency noise, impulse noise andcontinuous impulse noise, and adjust the cut-off frequency and output function adaptively according topacket delay listening results to realize the fast and accurate tracking to packet delay variation. Verified
by simulations on MATLAB, just as Fig 1 shows, the adaptive algorithm mentioned in this paper ismuch better than traditional filtering in tracking character, and meanwhile has almost the same filteringcharacter.
To sum up, the adaptive filtering algorithm putted forward by this paper, can make servo systems haveboth good tracking and filtering characters. Partly this paper provides a reference idea for applying theprotocol large-scale with low cost.

Fig 1: Output comparison of filtering and tracking between adaptive and traditional filtering

IFCS-EFTF5-PCD5-6

Precise Point Positioning technique for short and long baselines time transfer
P. Lejba1), J. Nawrocki1), D. Lemanski1), A. Foks-Ryznar1) , P. Nogas1) , P. Dunst1)
1)

Space Research Centre, Polish Academy of Sciences,

Astrogeodynamic Observatory, Borowiec, plejba@cbk.poznan.pl

In this work the clock parameters determination of several timing receivers TTS-4 (AOS),
ASHTECH Z-XII3T (OP, ORB, PTB, USNO) and SEPTENTRIO POLARX4TR (ORB, since February
11, 2012) by use of the Precise Point Positioning (PPP) technique were presented. The clock parameters
were determined for several time links based on the data delivered by time and frequency laboratories
mentioned above. The computations cover the period from June 1 to May 31, 2012 and were performedin two modes with 7-day and one-month solution for all links. All RINEX data files which include phaseand code GPS data were recorded in 30-second intervals. All calculations were performed by means of
Natural Resource Canada’s GPS Precise Point Positioning (GPS-PPP) software based on high-quality
precise satellite coordinates and satellite clock delivered by IGS as the final products. The received
results were compared with the results obtained by GPS CV, TWSTFT and optical fibre withstabilization of propagation delay.
The used independent PPP technique is a very powerful and simple method which allows forbetter control of antenna positions in AOS and a verification of other time transfer techniques like GPS
CV, GLONASS CV and TWSTFT. The PPP technique is also a very good alternative for calibration ofa glass fiber link PL-AOS realized at present by AOS. Currently PPP technique is one of the main timetransfer methods used at AOS what considerably improve and strengthen the quality of the Polish timescales UTC(AOS), UTC(PL), and TA(PL).

KEY-WORDS: Precise Point Positioning, GPS CV, TWSTFT, optical fibre, time transfer, IGS
products, GNSS, time scales.

IFCS-EFTF5-PCD5-7

The study of GPS Time Transfer Based on
Extended Kalman Filter
Wu Jian-feng1,2,3, Jing Wen-fang1,2,4,Hu Yong-hui1,2,3, He Zai-min1,2,3, Zhang fan1,2,3,4, Lv Hong-chun1,2,3,4
1.National Time Service Center, CAS, Xi’an 710600,China
2.Key Laboratory of Precision Navigation and Timing Technology, National Time Service Center, CAS, Xi’an 710600,China
3.Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, CAS, Xi’an 710600,China
4.University of Chinese Academy of Sciences, Beijing 100039,China

Abstract：The Global Positioning system (GPS) is global satellite navigation system that provides three major
functions of positioning, velocity measurement, and time transfer. The key of the precise time transfer is three
types of time synchronization which are the time synchronization between Universal Time Coordinated (UTC),GPS Time (GPST), satellite clock and user clock. GPS Time Transfer is a perfect combination of the advantagesof GPS atomic clock group and the receiver crystal oscillator. GPS atomic clock group can provide the time andfrequency of high accuracy and good long-term stability, and the receiver crystal oscillator can provide goodshort-term stability. In other words, the long-term stability of GPS timing receiver depends on GPS atomic clockgroup mostly. The short-term stability of GPS timing receiver is determined by the receiver crystal oscillator. But
is now mostly just used code pseudorange observation equation solving user clock offset in GPS timing receiver,while ignoring the impact of the receiver clock drift. In order to improve the GPS receiver Timing precision, thesingle satellite timing method is discussed, and the extended Kalman filter algorithm is used to estimate andpredict the clock offset and clock drift. GPS antenna position is fixed and known , and a receiver can determine
precise time by tracking a single satellite. The receiver clock model is constructed by the clock offset and clock
drift. The clock offset and clock drift have integral relationship, and often used as Kalman filter state variables.
The white noise spectral amplitudes of clock offset noise and clock drift noise can be related to the classical Allan
variance parameters Based on relationship between Allan Variances and Power spectral density Parameters.
Process-noise covariance matrix is deduced. The pseudorange-rate equation is derived according to pseudorange
observation equation. The pseudorange-rate is represented by the carrier phase difference of the adjacent sampling
time, and this method can improve the measurement accuracy of the Clock drift. The error source is analyzed andquantified with respect to the pseudorange and the pseudorange-rate, and the measurement noise covariancematrix is presented. The EKF method is tested and verified based on IGS data, and the timing precision of the
GPS single satellite can be improved through this method.
Keywords: kalman filter；the single satellite timing；clock offset；clock drift

IFCS-EFTF5-PCD5-8

A method of High precision time transfer based on DVB-S
Xiang Yu1,2,3, Hua Yu1,2,Xu Linshen1,2,Dong Daopeng1,2,3,Huang Changjiang1,2,3
2

1National Time Service Center, Chinese Academy of Sciences, Xi’an China
Key Laboratory of Precision Navigation and Timing Technology, NTSC,CAS, Xi’an , China
3
University of Chinese Academy of Sciences, Beijing China

This paper puts forward a method of high precise time transfer based on satellite digital TV
broadcasting system (DVB-S), with technology of television broadcasting, communication and timefrequency. Through intensive analyzing the digital satellite TV signals characteristic, and solving many
key problem such as insertion and broadcasting of timing signal in DVB-S, coding method of timing
signal, predict method of broadcasting delay of timing signal and capture-tracking method of timing
signal in receiver, the timing transfer method of high precision is proved practicable.
In this paper the high precise timing is achieved through such steps as fellow:(1) Program clock reference(PCR) in the TS of DVB-S is proposed as the flag bit;(2) Each PCR is given a high precise timing stamp in transmitter and receiver;(3) The accurate position of the broadcasting satellite in the orbit is provided by NTSC’s the realtime observation, then sended with timing stamp to receiver via the satellite after coding;(4) The coding is received and decoded by user, then the PCR is also given another time stamp in
the local time system. The cute synchronization is achieved with the information both the accurate
position of satellite and the two timing stamps;(5) The local time system is synchronized accurately with the transmitter time system after the
calculation with the signal delay, satellite accurate position and user position.
The formula is shown :Tu _ pcr  t s _ pcr  (t r _ pcr  t s _ pcr ) 2   c   ion   tro   oth ………………(1)Which:
Tu _ pcr user time;t s _ pcr time of transacting PCR in transaction end;t r _ pcr time of receiving PCR in transaction end; distance of satellite to user; ion ,  tro delays of ionosphere and troposphere effects;
At the end of 2011, the result of tests in five cities in China (Nanjing, Xi 'an, Urumqi, Changchun,
Haikou) proves synchronization accuracy < 100 ns (1  ).

IFCS-EFTF5-PCD5-9

A simple computation technique for improving the short term
stability and the robustness of GPS TAIP3 Common-Views
G. D. Rovera, B. Chupin, M. Abgrall and P. Uhrich
LNE-SYRTE, CNRS, UPMC, Observatoire de Paris, 61 avenue de l’Observatoire, 75014 Paris, France

Email: Daniele.Rovera@obspm.fr
The Observatoire de Paris (LNE-SYRTE) is the institute designated by the French National Metrology
Institute (NMI) Laboratoire National de Métrologie et d’Essais (LNE) in the field of Time andFrequency Metrology. In this frame, the laboratory has a long history in developing remote clock
comparisons by using the well-known Common-View (CV) technique on signals from the Global
Positioning System (GPS)1. In order to improve the short term stability of GPS CV by using data in the
CGGTTS TAIP32 format, we propose here a new averaging technique.
From CGGTTS GPS TAIP3 CV daily files between two remote stations, we compute a linear fit, and weaverage out all 3 sigma outliers in an iterative process without any limitation. This allows to suppress
either “bad” CV due to some problems in the reception of a given satellite signal, or CV exhibiting
abnormal high noise, or any unusual outliers. A mean value between the remaining CV is then computedfor each common CGGTTS epoch, leading to the timetransfer results for the remote time scales.
We have applied this new technique on two typicallinks: a short baseline between OP and PTB(Braunschweig, Germany), and a long baseline
between OP and USNO (Washington, USA). As
expected, the short term noise over a short baseline isonly marginally improved compared to the resultsfrom the former processing1, but the average numberof remaining CV between remote stations after
filtering of the outliers is twice as large for a given
epoch, increasing that way the time transfer
robustness. Over a long baseline, as can be seen on
Fig. 1, we obtain a short term noise in terms of Allan
Time Deviation (TDEV) twice smaller for averaging
periods from about 10 000 s to 1 d, the TDEV
reaching about 300 ps at 1 d, together with an averageincrease of 20 % on the remaining CV after filteringof the outliers.

Fig. 146: TDEV comparison of CGGTTS GPS
TAIP3 CV between UTC(USNO) and UTC(OP)over 100 d when applying either the Kronide
software developed years ago1 or the new 3 sigma
filtering technique over daily files.

Hence in all cases, this new simple technique improves the short term noise of time transfer andincreases robustness simultaneously, the improvement depending on the baseline. This technique mightalso be useful for any upcoming new GNSS time transfer based on code data.
___________________________
1

J. Achkar, P. Uhrich, Ph. Merck and D. Valat, “Recent Time and Frequency Transfer Activities at the Observatoire deParis”, Proc. of the 2005 IEEE Frequency Control Symposium and Annual Precise Time and Time Interval Meeting,Vancouver, 2005.
2

P. Defraigne and G. Petit, “Time transfer to TAI using geodetic receivers”, Metrologia 40 (2003) 184-188.

IFCS-EFTF5-PCD5-10

Design and Implementation of Dual One-way Precise Ranging andTime Synchronization System
1,2,3

1,2,3,4

1,2,3,4

1,2,3

1,2,3

1,2,3,4Hong-Jiao Ma , HuaBing Wu, Meng Li, ZaiMing He , JianFeng Wu , Kang Wang
1
National Time Center, Chinese Academy of Sciences, Xi’an, Shaanxi, China
2
Key Laboratory of Precise Navigation and Timing Technology, CAS, Xi'an, Shaanxi, China
3
Key Laboratory of Time and Frequency Primary Standards, CAS, Xi'an, Shaanxi, China
4

University of Chinese Academy of Sciences, Beijing, China
Email: mahj@ntsc.ac.cn

Abstract: With the development of science technique in aeronautic and astronautic testing navigation,communication, as well as electric power, etc, time synchronization has been needed in more and moreengineers and sciences fields. Dual one-way ranging can get more veracity of measure precision than
one-way due to eliminating the common measure error between two points. This article describes theuse of dual one-way pseudo-code and carrier phase precise measurement for realizing timesynchronization technique. The results from experiment show that ranging and time synchronization
resolution of system reach 0.15cm and 5ps in 1s time interval, its precision reach 3.46ns or 9.43ps using
different or same frequency reference of the order of e-11/d respectively. Dual one-way ranging andtime synchronization can be applied in aeronautic and astronautic measurement and control system, andin achieving high precision time platform in message transfer field. It also can provide time service
between satellite and satellite, satellite and ground station, aircrafts, stations and other patterns.
Key words: Precise Ranging; Time Synchronization; Dual One-way Ranging Measurement.

IFCS-EFTF5-PCD5-11

Analysis on GNSS space clocks performances
A.Cernigliaro3, S. Valloreia1, L. Galleani1, P. Tavella2
1

Politecnico di Torino, Torino, Italy
2
INRIM, Torino, Italy
3
Aizoon, Torino, Italy
Email: a.cernigliaro@inrim.it

In Global Navigation Satellite Systems (GNSS) the role of atomic clocks is essential for thedetermination of the user position. Nowadays, several satellite navigation systems are operating anddifferent clock technologies have been employed on board satellites, taking benefit of the improvements
reached during the last decades. The analysis of GNSS clock performance is thus crucial for ensuring
the GNSS positioning and timing capabilities.
We performed an analysis on the clock estimates generated by the Information-Analytical Centre
437(IAC) of the Russian Federal Space Agency, which provides a service similar to the one of theInternational GNSS Service (IGS). Therefore, we collected and processed the RINEX for clock files
containing satellite clock estimates for GPS and GLONASS constellations, from 2010 to 2012: with our
statistical tools438 we made a comparative analysis on the performances of the different clock
technologies employed on board (RAFS, Cesium clocks), and of the different navigation systems. In
particular, we focused the attention on the clock frequency behaviour and the frequency stability,
evaluating also the stationarity of these characteristics. Besides, an assessment of experimental on board
clock data with respect to the theoretical deterministic and stochastic behaviour of the atomic clock, asobtained from clock specifications, is reported.
Our results show that some aspects are common to the different clock types and navigation systems,
while some differences can be observed in the different families.

437

438

http://www.glonass-ianc.rsa.ru/en/

A.Cernigliaro, I.Sesia, "Satellite Clocks Characterization and Monitoring for Global Navigation Satellite Systems",
in Proc of the XXX URSI General Assembly and Scientific Symposium of International Union of Radio Science, August
13th-20th 2011, Istanbul, Turkey

IFCS-EFTF5-PCD5-12

A Method of GNSS System Time Offset Monitoring
Huijun Zhang1,2, Lin Zhu1,2,3, Xue Zhang1,2,3, Xiaohui Li1,2
12

National Time Service Center, Chinese Academy of Sciences, Xi’an, China
Key Laboratory of Precision Navigation and Timing Technology, National Time Service Center,
Chinese Academy of Sciences, Xi’an, China
3
University of Chinese Academy of Sciences, Beijing, China
Email: zhj@ntsc.ac.cn

With the progress of Global Navigation Satellite System(GNSS),which mainly include
GPS,GLONASS,GALILEO as well as BeiDou, multi-system joint working mode has become research
focus and application trend. But, Each satellite navigation system has its own independent system time,such as GPST,GLONASST,GST and BDT. The System time offset between the two satellite navigation
systems is one of the most important aspects of their interoperability. It will cause combined navigation
position solution bias. Therefore, it is necessary and significant to monitor and research system timeoffset.
A method of GNSS System Time Offset monitoring which is called signal- in-space receiving method is
put forward and its principle is described. In this method, UTC(NTSC) time scale is regarded as
reference time scale on account of its status of standard time and frequency resources. Then, The timeoffset between each satellite navigation system time and UTC(NTSC) which include UTC(NTSC)GPST,UTC(NTSC)-GLONASST,UTC(NTSC)-BDT,UTC(NTSC)-GST can be acquired. Thus, systemtime offset among satellite navigation systems, such as GPST-GLONASST, can be acquired with the
5ns (1σ) precision.
On the basis of above described method, GNSS System time offset monitoring system has been set up
since 2011 and it is gradually improved and perfected. A great deal of monitoring data has beencollected. Addition to common error sources, some special error sources related to GNSS timing
receiver such as receiver delay, inter-system hard delay bias, inter-frequency biases and so on are
analyzed, as they can effectively affect monitoring results and precision. The monitoring data and IGS
precision orbit and clock bias data as well as corresponding data published by BIPM Circular T Bulletin
are combined together to determine above error values. The results of the error items and GNSS systemtime offset monitoring results are to be showed.

IFCS-EFTF5-PCD5-13

Implementation of the Real-Time Multi-Channel ADEV, TDEV, and
HDEV Computation Methods
Michal Kasznia
Poznan University of Technology, Poznan, Poland
Email: mkasznia@et.put.poznan.pl
Proper quality of timing (synchronization) signals in the telecommunication network is a necessary
condition of the effective data transmission throughout the network. In order to examine this quality
several parameters are computed using the sequences of time error samples measured at some network
interface. Allan deviation ADEV and time deviation TDEV allow the variations of time interval
provided by the synchronization signal to be assessed and the type of phase noise affecting the signal tobe recognized. Hadamard deviation HDEV is insensitive for the presence of frequency drift and can beused for recognition of higher types of phase noises. The application of real-time computation of theseparameters performed during time error measurement process allows to simplify the evaluation
procedure.
One may occur, that more than one timing signal has to be analyzed in the same time. Such situation canbe considered in the node of the telecommunication network, where the signals arrive from several
directions, or when we want to perform the three cornered hat procedure. A multi-channel time error
meter with computation algorithms applied could be suitable for this analysis.
The computation methods enabling assessment of the parameters in the real time were proposed andtested439,440. The experimental tests have proved the ability of the computation of these parameters in thereal time for a single data series as well as for multi-channel time error measurement.
In the paper the results of the implementation of the algorithms enabling real-time ADEV, TDEV, and
HDEV assessment during multi-channel time error measurement are presented. To test these methods ina real measurement process, a special measuring system SP-4000 was used441. This system, designed
and developed in the laboratories of Poznan University of Technology, enables multi-channel time error
measurement. Several conditions were considered during the implementation: number of measurement
channels, values and ranges of observation intervals considered, data structures and its organization.
Some hardware and software solutions enabling to join the time error measurement and parameters’
computation in one effective process are discussed and suggested.

439

A. Dobrogowski, M. Kasznia, “Joint real-time computation of Allan deviation, time deviation, and Hadamard deviation”,
Proc. of 24th European Frequency and Time Forum, 13-16 April 2000, Noordwijk, Netherlands.
440

M. Kasznia, “Multi-channel real-time computation of ADEV and TDEV”, Proc. of 24th European Frequency and Time
Forum, 13-16 April 2000, Noordwijk, Netherlands.
441

A. Dobrogowski, M. Kasznia, M. Jessa, K. Lange, M. Jaworski, „Hardware and software realization of time terror
measurements with real-time assessment of ADEV, TDEV, and MTIE”, Proc. of 24th European Frequency and Time Forum,
13-16 April 2000, Noordwijk, Netherlands.

IFCS-EFTF5-PCD5-14

Experimental Tests of the Real-Time MTIE Assessment Methods
for Multi-Channel Time Error Measurement
Andrzej Dobrogowski, Michal Kasznia
Poznan University of Technology, Poznan, Poland
Email: mkasznia@et.put.poznan.pl
Maximum Time Interval Error (MTIE) is one of the parameters describing the quality of thetelecommunication network timing signals. MTIE identifies maximal phase differences withinconsidered observation intervals and therefore it is well suited for dimensioning of buffers (elastic
stores) at the boundaries of the time scales. This parameter can be computed off-line, following the timeerror measurement process as well as in the real time, during the time error measurement442,443.
The maintenance of the telecommunication network often requires the analysis of several timing signals
in the telecommunication network node performed in the same time. A multi-channel time error meterwith computation algorithms applied could be suitable for this analysis.
Authors of this paper have proposed and described444 two methods enabling MTIE assessment
performed in the real time for multi-channel time error measurement. First solution is based on the timeeffective MTIE computation method with binary decomposition445. This method offers regularly anddata-independent running data reduction which can be effectively applied for the real-time multi-channel
computation. Second solution exploits the time effective extreme fix (EF) method successfully appliedearlier for single-channel real-time MTIE assessment2. According to this method, the computation forsome observation intervals may be suspended in order to reduce the number of operations carried out
within the duration of one sampling interval. The analysis of suspended intervals is performed when themeasurement is finished.
In order to compute the MTIE estimate simultaneously for several observation intervals and several data
series (obtained from the measurement channels) in the real time, all necessary operations have to bedone in the time interval between two successive time error samples, i.e. during the sampling interval 0.
The ability of real-time assessment depends on the several conditions: number and length of theobservation intervals considered, number of measurement channels, data structures and organization,
computation ability of the equipment, and time error data behavior.
In the paper the results of experimental tests of these methods are presented. The calculations were
performed for several data sequences representing different behavior of time error taken with samplinginterval 0=1/30 s, which is often used in the telecommunication applications. The results of calculation
for different conditions using both methods are presented and discussed.

442

A. Dobrogowski, M. Kasznia, “On-line computation of MTIE using binary decomposition and direct search withsequential data reducing,” Proc. of the 2007 IEEE IFCS and EFTF, pp. 877-882, 29 May – 01 June 2007, Geneva.
443

A. Dobrogowski, M. Kasznia, “Implementation of Real-Time MTIE Assessment Method”, Proc. of 2011 Joint Conferenceof the IEEE FCS and EFTF, pp. 304-309, May 2-5, 2011, San Francisco, California, USA
444

A. Dobrogowski, M. Kasznia, “Some Concepts of the Real-Time MTIE Assessment for Multi-Channel Time Error
Measurement,” Proc. of 2012 IEEE IFCS, pp. 493-498, May 22-24, 2012, Baltimore, USA,445

S. Bregni, S. Maccabruni, “Fast computation of Maximum Time Interval Error by binary decomposition,” IEEE Trans.
Instrum. Meas., vol. 49, No. 6, pp. 1240-1244, Dec. 2000.

IFCS-EFTF5-PCD5-15

Application of three-cornered-hat method
for estimation uncertainties type uA and uBof time measurement instruments
S.Bolginova, N.Koshelyaevsky, S.Pesterev, N.Pol’nikov, E.Popkova
The Main Metrology Center of the State Time and Frequency Service
FGUP “VNIIFTRI,” Mendeleevo, Moscow region, Russia
email: nkoshelyaevsky@vniiftri.ru
The accurate estimations uncertainties type uA and uB in time measurement instruments is very
important because of at next step these transform in performances of time and frequency standards.
The usual methods [1, 2, 3] based on feeding device under test by frequency/time signals fromthe same source as a matter of fact produce very rough approximation, and typically overestimated, toactual values of uncertainties type uA and uB.
On other hand quite often laboratories posses several T&F measuring instruments of the same
type with similar performances, but do not have more perfect and accurate instruments to calibrate theseones.
The three-cornered-hat method does require neither high accurate reference instrument, nor apriori knowledge of time/frequency relations of signals used in measurements.
The paper will deliver several examples of estimations uncertainties type uA and uB for different
types of phase comparators and time interval meters. For the best instruments obtained uncertainties
type uA and uB are in conformity with claimed performances.
References
4. Time interval meter I4-10, Manuals, E32.817.040, chapter 15.5.8 and 15.5.9
5. Unit of phase comparators, Manual, E32.721.701, chapter 15.5.6
6. Multichannel phase comparators, Manual, ЯКУР 411146.018, chapter 5.8.3.1

IFCS-EFTF5-PCD5-16

A Novel Timing-Delay Measuring Method Based On PN Code in
Telephone Time Service
1,2

Dong Dao-peng

1,2, Zeng Ting

1,2

, Xiang Yu

1,2, Huang Chang-Jiang(1．National Time Service Center，Chinese Academy of Sciences，xi’an 710600 China;
2．Graduate University of Chinese Academy of Sciences，Beijing 100039 China)

The key problem of telephone time service by PSTN is how to synchronize user time with standard time,in other words, measuring time delay of transmission is the important problem. Now, there are two
methods of measuring time delay, the first way is by transmitting character signal; the second way isthrough phase-detecting. The precision of measuring time delay will have a directly influence on system
synchronization time precision, also, The traditional analog modulation/demodulation will highly effectthe precision, but the phase error is inevitably because of the effect caused by the noise and channel
characteristic when using phase-detecting.
The new method, using correlation of PN code will be presented in this paper. The delay time can be got
by detecting the peak of the correlate function. The server will transmit PN code to the user, the user end
will generate the local code with some time difference, which is same as transmit code .Then compared
local code with received PN code bit by bit, the correlation value will be got. It can be seen second
signal have synchronized when the correlation value reach to the maximum, which only include one
transmit delay Δt. At this time the user will send generated PN code to the server again, operated
correlatively with PN code generated by server, the time difference between server and user can be
confirmed through measuring the position of correlative peak. Suppose the delay of transmit and receive
is consistent, the gotten time difference divided by two is transmission delay.
The correlation of PN code is depended on the type and length of code. It was analyzed that thecorrelation of PN code and local code will close to 1/p of maximum output when received PN code andnative code is a gap of one code element, and the output is maximal when time discrepancy is equal tozero. Moreover, the correlation value will change according to the time discrepancy when time
discrepancy is in a positive code or a negative code. Also in a sequence period, the correlation value
varies evidently in a code, but no change in other time.
The synchronization of PN code is divided into coarse synchronizing and accurate synchronizing, whichmeans the capture and track of PN code. It is the capture of PN code that make local pseudocode
synchronize with received code, which can attain the precision of 1/2 width in one code. However,according to the need of measuring time delay, the received signal must be farther tracked so as toimprove the precision. The track of PN code can control the synchronized precision to more small code
period range, so the precise time delay will be gotten.
Measuring time delay based on PN code in telephone time service has many advantages, high accuracyof detection; good resist noise interference capability; simple to implement. It can solve many
disadvantages on existing measure transmission delay effectively, and enhance precision of timesynchronization.

IFCS-EFTF5-PCD5-17

VLBI receiver chain monitoringVojtěch Michálek1, Jan Kodet2, Ulrich Schreiber2, Christian Plötz3, Ivan Procházka1, Petr Pánek4
1

Czech Technical University in Prague, Břehová 7, 115 19 Prague 1, Czech RepublicTechnische Universität München, Wettzell Observatory, 93444 Bad Koetzting, Germany
3
Bundesamt für Kartographie und Geodäsie, Geodätisches Observatorium Wettzell, Germany
4
Institute of Photonics and Electronics, Chaberská 57, 182 51, Prague, Czech Republic
2

Email: kodet@fs.wettzell.de
The most demanding goal of the Global Geodetic Observing System initiative is the definition of station
positions to an accuracy of 1 mm and the corresponding velocities to 0.1 mm/year. The main remaining
sources of error are caused by systematics, leading to intra- and inter- technique biases. In this work, wehave focused on Very Long Base Interferometry (VLBI) and phase calibration generator currently inoperation. This unit is injecting calibration tones into the detection chain through an input coupler
located near the input of the antenna. The tones propagate further through entire detection chain and arerecorded with the observed signal. Then they are extracted in post processing. These tones are generated
out of an atomic frequency standard. The supplied frequency is significantly influenced by temperatureand mechanical changes since usually a long cable is employed to bring the frequency to the calibration
unit. To monitor the electrical length of the cable, calibration with a picosecond precision is essential.
We have redesigned a phase calibration unit so that it enables the implementation of the Two Way Time
Transfer (TWTT) method on single coaxial cable using two event timers to monitor the electrical lengthof the critical cable. Such a system has been installed in parallel to the unit currently in operation.
Preliminary experiments suggest, that such a technique can be used for monitoring of the electrical cable
length with precision of one picosecond of rms. The comparison of the TWTT method with previous
measurement method is presented.

IFCS-EFTF5-PCD5-18

An Algorithm with Periodic Item for
Steering UTC(NTSC) to UTC
REN Ye1,2 , LI Xiao-hui1,2,XUE Yan-rong1,2,3 ,LI Yu-wei1,212National Time Service Centre, Chinese academy of Sciences, Xi’an，China

Key Laboratory of Precision Navigation and Timing , National Time Service Centre,
Chinese academy of Sciences, Xi’an,China
3
Graduate University of Chinese Academy of Sciences, Beijing， China
Email: renye@ntsc.ac.cn,

In order to steer master clock in timekeeping laboratory, it is necessary to identify a suitable algorithm
for steering UTC(NTSC) to UTC for a period of 45 days. By representing residual term as a series of
periodic item in a quadratic polynomial model, a modified model is established and it is used to predict
UTC-UTC(NTSC) time offest. In this case, two considerations, rank of periodic item and data size, areconsidered. Moreover, two kinds of spectrum analysis, peiodogram and correlogram, is discussed to
identify a proper rank of periodic item and a . The analysis illustrate that the modified model based oncorrelogram with 12 months data shows plausible results in terms of both stability and accuracy.

15

Residual (ns)10

Quadratic Polynomial
Periodogram
Correlogram

5

0

-5

-10

-15
55749

55779

55809

55839

55869

55899

55929

55959

55989

56019

56049

56079

MJD

Fig. 147: The predicted residual based on three fitting steering algorithm (quadratic
polynomial model, modified model with pariodogram, modified model with correlogram)from July 2011 to June 2012

IFCS-EFTF5-PCD5-19

Progress in the link calibration for UTC time transfer
Z Jiang1, G Petit1, L Tissearant1, P Uhrich2, G D Rovera2 and S Y Lin3
1 Time Department, Bureau International des Poids et Mesures (BIPM), Pavillon de Breteuil F-92312,
SÈVRES CEDEX, France
2 Laboratoire National de Métrologie et d’Essais-Systèmes de Référence Temps-Espace (LNE-SYRTE),
CNRS, UPMC, Observatoire de Paris, France
3 National Standard Time and Frequency Laboratory, Telcommunication Laboratories (TL), Chunghwa
Telecomzjiang@bipm.org

The dominant part of the total uncertainty budget in the [UTC-UTC(k)] is from the time transfer
calibration. In 2011, the International Bureau of Weights and Measures (BIPM) launched a pilot
experiment aiming at improving the calibrations using the link calibration method, in particular for the
Asia-Europe very long baselines. The goal is to reach the expected type B uncertainty to be less than 2
ns. In this frame, the BIPM developed a standard calibration scheme in which an integrated and precabled portable calibration station is used. It is composed of a 10 MHz distributor, a PPS distributor and
two GNSS geodetic setups each include a set of independent receiver, antenna and cables. Other
receivers are stationary at the BIPM for start and closure checks. Using this system, we performed sometests on zero and short baselines at the BIPM between the present time laboratory and the new one, andbetween the BIPM and the LNE-SYRTE in Observatoire de Paris. Another experiment using the same
scheme is carried out by TL (National Standard Time and Frequency Lab. Telecommunication
Laboratories). In this paper, we present the results of these studies. We analyze the uncertainties of thislink calibration and compare them to the traditional differential receiver calibration methods.
Key Words: UTC, Time transfer, Calibration

IFCS-EFTF5-PCD5-20

Research on precision measurement of phase difference
between different frequency signals

Miao Miao1, Wei Zhou1, Xueping Zhang1, Zhiqi Li1, Changsheng Liu1
1

Department of Measurement and Instrument, Xidian University, Xi’an, P.R. China
Email: mmiao@mail.xidian.edu.cn

Traditional phase comparison must be carried out between the two frequency sources with the samevalues. However, recent researches have found that phase comparison also can be implemented between
frequency sources with different values and obtain higher resolution.
The paper analyzes the phase difference regularity of arbitrary period signals’ comparison. Discuss indetail that fine quantized phase step phenomenon and how the step value to reflect the higher resolution.
When two signals with different frequencies are compared, their phase differences are in special orderaccording to the frequency ratio, and, because of small frequency deviation existing, corresponding
phase differences in every least common multiple period are different. As for the equivalent phase1
discrimination frequency, ABfmaxc *, has very high resolution, under the condition of proper reference
frequency, the technology in the paper can reach higher measuring resolution. As for the development ofpresent base standard sources and the research on fine quantified phase step phenomenon between
period signals, the signal comparison in RF band could reach ps resolution and even fs. Because thehardware used in detecting coincidence information will bring some trigger error and compared signals’
own noise will bring some phase uncertainty, the software in connection with algorithm can be used in
the technology. On account of instruments’ own drift, pulse average method and pulse filling method
can be used, and moreover, self-calibration.
*: When the frequency values of compared signals are respectively f1 and f2 and their greatest common
factor frequency is fmaxc, f1=Afmaxc，f2=Bfmaxc.

IFCS-EFTF5-PCD5-21

NTP Accuracy in Practice
Demetrios Matsakis1
1

United States Naval Observatory, Washington, DC, USA
Email: dnm@usno.navy.mil

Over three years of Network Timing Protocol (NTP) timing data will be presented and analyzed for
accuracy. Data are presented from UNIX, LINUX, and MAC clients, and from the USNO facilities in
Washington DC, the Alternate Master Clock (AMC) in Colorado Springs, Colorado, as well as two
private locations in the DC area. These clients are used to extract time from servers maintained by
USNO, NIST, and other timing centers in the USA, Europe, and Asia under the assumption that theservers are synchronized to the accuracy far better than observable via NTP.

IFCS-EFTF5-PCD5-22

Time and frequency distribution improving in Calern/Geoazurlaboratory for T2L2 campaign
Myrtille Laas-Bourez1, Daniele Rovera2, Michel Abgrall2, Etienne Samain1, Jean-Louis Oneto1, Philippe
Guillemot3
1

Géoazur, Université de Nice Sophia-Antipolis, Observatoire de la Côte d’Azur, Centre National de laRecherche Scientifique (UMR 7329), 250 av. Einstein 06560 Valbonne, France
2
LNE-SYRTE, Observatoire de Paris, UPMC, UMR CNRS 8630, 61 av. de l'Observatoire, 75014 Paris,
France3
CNES, French Space Agency, Toulouse, France
Email: Myrtille.Laas-Bourez@oca.eu
The Time Transfer by Laser Link (T2L2) 446 experiment aim to synchronise remote ultra stable clocks
over large-scaled distances using two laser ranging stations. T2L2 ultimate time transfer capability can
only be demonstrate with a picosecond range ground mastering. We focus this year in knowledge andequipment improvement to perform a T2L2 time transfer with accuracy and stability of a few
picoseconds.
A deep analysis of signals stability has been carried out this year in the time and frequency laboratory in
Plateau de Calern. The aim was to better understand the limits and hardware configuration and toenhance time and frequency distribution for T2L2 experiment. We showed phase noise and stability
problem on our H-maser distribution. Final measures were conducted in October in collaboration withSYRTE. Then a complete equipment reorganisation was done.
This paper focus on the time and frequency laboratory characterization before and after the
reorganisation. We introduce our new equipments and present our new H-maser time scale and discuss
the performances obtained.

446

E. Samain, “T2L2: ground to ground Time Transfer”, EFTF 2012, Goteborg, Sweden, 23-37 may 2012.

IFCS-EFTF5-PCD5-23

Synchronization of Ultrafast Lasers
Huan Zhao, Jun Ge, Nuan-rang Wang
Science and Technology on Metrology and Calibration Laboratory, Beijing Institute of Radio Metrology& Measurement, Beijing 100854, China
Email: huanzhao@sina.com
Timing synchronization between femtosecond lasers is indispensable in various scientific researches. This
Letter reports our work on highly precise active synchronization between two independent femtosecond
Ti:sapphire lasers based on a combination scheme of three phase locked loops(PLLs). The lasers are firstly
synchronized by two PLLs at relative large timing-jitter, then the sum frequency generation(SFG) signal of
the two lasers is fed back to the above PLLs, which acts as the third PLL and improves the precision of thesynchronization significantly.
TWINⅠ
PIN

BPF

DBM

OPA

PLL1 OPA227
from LF
to PA45

TWINⅡ
Udc
to PZT1

PA45 OPA227

LF

Uin
Subtracter

Uout

LF MAX400

to PZT2

Fig.2 slave PLL(PLL2)
Fig.1 masterIn the experiment,
we made two self-mode-locked Ti:sapphire lasers named as TWINⅠ and TWIN Ⅱ with
PLL(PLL1)
similar schemexxiii. There are two piezoelectric actuators(PZT) with different maximum displacement andresponse velocity, either of which is attached with a cavity mirror inside the laser separately. Since therepetition rate depends on the cavity length of the laser, the PLL can compensate the relative variation of thecavity length and then synchronize the two trains of femtosecond laser pulses precisely by controlling thedisplacement of the PZT. The master PLL(PLL1, shown in fig.1) works for primary synchronization and theslave PLL(PLL2, shown in fig.2) maintains long-term stability, the PLL2 can work together with PLL1 bycontrolling the loop gain. Once these two PLLs activate normally, TWINⅠand TWIN Ⅱ could output
synchronized laser pulses trains stably. However, the timing jitter is about hundreds of femtoseconds, which
is obviously too large compared to the 100fs laser pulse width, thus we should improve the precision ofsynchronization further for the practical application.
When TWINⅠ and TWIN Ⅱ are synchronized by theAD711 LF
Uout
two PLLs mentioned above, we focus two laser beams Udc
1
AP
Subtracter
into a nonlinear crystal to generate sum frequency laser.
Uin
The SFG Laser signal intensity is very sensitive to the SFG Laser
LF
temporal position of the laser pulses, much more sensitive
to OPA227
2
than the output of DBM in PLL1. If feeding this SFG
from DBM
PLL1
signal back to the above PLLs, which acts as an optical
PLL(PLL3, shown in fig.3), it could improve theFig.3 opticalprecision of active synchronization significantly. Once
PLL(PLL3)
PLL3 activates normally together with PLL1 and PLL2, the timing jitter of TWINⅠ and TWIN Ⅱ could
reduce to tens of femtoseconds. We have measured the precision of synchronization with correlation
methodxxiv, and the calculated rms timing jitter is about 30fs within 10s measurement time, which means theprecision of the synchronization is improved significantly up one order of magnitude.

IFCS-EFTF5-PCD5-24

Multipoint dissemination of RF frequency in delay-stabilized fiber
optic link in a side-branch configurationŚliwczyński Ł, Krehlik P, Buczek Ł, Lipiński M
Department of Electrical Engineering, AGH University of Science and Technology, Kraków, Poland
Email: krehlik@agh.edu.pl
Recently our group proposed a method of tapping an RF frequency signal447 from a fiber optic dissemination
link with the stabilization of the propagation delay448. In its basic configuration this gives an access to justthe points located along the trunk fiber that connects the Local and the Remote Modules. We tested thisapproach at our lab obtaining the residual instability of the frequency transfer at both the main and tapped
outputs around 210-17 at 105 s averaging.
The idea of tapping the frequency signal from the delay-stabilized link is flexible and may be further
expanded into a tree-like structure including so-called side-branches, allowing disseminating the frequency
signal to the points that do not lie on the route of the trunk fiber. The side-branch fiber may be tapped as welland even equipped with subsequent side-branches. The network built with such a technology may cover large
areas, giving the access to the same, high quality clock to many distributed users.
In this paper we present for the first time the experimental data concerning the stability of the frequency

Fig. 148: An example of the delay-stabilized fiber optic network for multipoint frequency
dissemination exploiting simple taps as well as side-branches. In entire network the propagation delay
from the input to each output is stabilized.

signal at the output of the branch, measured on both a field-deployed and spooled fibers. The measurements
are performed having all the Local, Remote and Branch Output Modules at the same laboratory, because thisis the only way to examine the stability of the dissemination without using any additional transfer system thatwill incur the obtained results. We are also discussing the problem of degradation of the signal at the Branch
Output depending on the length of the side-branch and location of the Branch-Side Tap.
Acknowledgment
This work was supported by Polish National Science Centre under the decision DEC-2011/03/B/ST7/01833.

447

P. Krehlik, Ł. Śliwczyński, Ł. Buczek, M. Lipiński, “Multipoint dissemination of RF frequency in fiber optic link withstabilized propagation delay”, paper submitted to IEEE Trans. UFFC, 2013448

Ł. Śliwczyński, P. Krehlik, Ł. Buczek, M. Lipiński, “Active propagation delay stabilization for fiber optic frequency
distribution using controlled electronic delay lines”, IEEE Trans. Instr. Meas., vol. 60, pp. 1480-1488, 2011

IFCS-EFTF5-PCD5-25

Evaluation of the AGH-designed Time and Frequency transfer
system on a 149 km PTB-Hannover-PTB fiber link
P. Krehlik1, G. Grosche2, S. Raupach2, D. Piester2, H. Schnatz2, Ł. Śliwczyński1
1

2

AGH University of Science and Technology, Mickiewicza 30, 30-057 Krakow, Poland
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
Email: sliwczyn@agh.edu.pl

We describe experiments with the AGH-designed fiber optic system for time and frequency
dissemination, based on active stabilization of the fiber delay449,450. The measurements were performedat the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, over a field-deployed optical fiber
loop going from PTB to the Magnesium clock laboratory in the Leibniz Universität Hannover (LUH)451
and back (149 km, 45 dB attenuation). Both the transmitting and receiving modules of the system werelocated in the same laboratory, allowing accurate measurements of the system performance.
We detected strong optical reflections (> -20 dB) within the last-mile fiber hops at LUH, at both sides ofour bi-directional optical amplifier installed at LUH. The multiple reflections in the vicinity of theamplifier caused severe degradation of the intensity-modulated optical signals, or even lasing of theamplifier, making accurate time dissemination impossible. However, inserting a wavelength selective
optical isolation module at one side of the amplifier proved to be very effective, breaking the resonant
structure and eliminating signal distortions. Thus, for the first time, we undertook measurements in thepresence of strong reflections in the optical path.
To assess the fiber link stabilization, we simultaneously used different measurement methods. We
measured the instability of a10 MHz frequency signal with a dual mixer and harmonic tracker systemdeveloped at PTB. Simultaneously, we measured 100 PPS time signals with either a standard timeinterval counter, or a high-speed digital oscilloscope controlled by dedicated software. The modified
Allan deviation (MADEV) for 10 MHz frequency signal was approaching 10-17 at one-day averaging
and the time deviation (TDEV) of 100 PPS remained below 1 ps over the measurement duration. The
outstanding results obtained for the time transfer are partly due to using 100 PPS instead of 1 PPS, thus
averaging short-term noise of both the measurement setup and the transmission system.
We also performed a check of absolute calibration of the time transfer, and found only 18 ps difference
between 100 PPS input-to-output delay measured directly, and obtained from a calibration procedure,
which uses only the data available at the transmitting side of the system1.
Acknowledgement:This work was supported by the European Metrological Research Programme EMRP under SIB-02 NEAT-FT. The EMRP is
jointly funded by the EMRP participating countries within EURAMET and the European Union. We thank Steffen Rühmannfrom LUH for his invaluable technical help.

449

P. Krehlik, Ł. Śliwczyński, Ł. Buczek and M. Lipiński, “Fiber optic joint time and frequency transfer with active
stabilization of the propagation delay”, IEEE Trans. Instrum. Meas. 61, 2844–2851, 2012.
450

Ł Śliwczyński, P. Krehlik, A. Czubla, Ł. Buczek and M. Lipiński, “Dissemination of time and RF frequency via astabilized fibre optic link over a distance of 420 km”, Metrologia 50, 133-145, 2013.
451

A. Pape, O. Terra, J. Friebe, M. Riedmann, T. Wübbena, E. M. Rasel, K. Predehl, T. Legero, B. Lipphardt, H. Schnatz,
and G. Grosche, “Long-distance remote comparison of ultrastable optical frequencies with 10−15 instability in fractions of asecond“, Optics Express 20, 21477-21483, 2010

IFCS-EFTF5-PCD5-26

Bi-directional optical amplifiers for long-distance fibre links
Sebastian M. F. Raupach1, Andreas Koczwara1, Gesine Grosche1, Fabio Stefani2, Olivier
Lopez2, Anne Amy-Klein2, Christian Chardonnet2, Paul-Eric Pottie3, and Giorgio Santarelli3,41

Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
2

LPL, Université Paris 13, Sorbonne Paris Cité, CNRS, Villetaneuse, France
3

4

LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France

LP2N, Université de Bordeaux 1, Institut d’Optique and CNRS, Talence, France
Email: sebastian.raupach@ptb.de,Within the European Metrology Research Programme (EMRP), project “NEAT-FT” aims at developing
instrumentation for ultra-stable long-distance frequency transfer via optical fibre networks, such as special
amplifiers adapted to bi-directional optical frequency transfer452,453.
Two approaches are followed, one based on Erbium-Doped Fibre Amplifiers (EDFA), the second on Fibre
Brillouin Amplifiers (FBA). Both systems are intended for deployment along a fibre link that will connect
PTB/Germany and SYRTE/France.
EDFA are widely used amplifiers for telecommunication. Due to their sensitivity to backscattering and backreflections, EDFA are commonly equipped with optical isolators making them uni-directional devices. Here
we report on fully bi-directional EDFA with a maximum gain of 20 dB and improved optical filtering to limit
ASE and conditions of self-oscillations. Additionally, remote control was implemented for these special
amplifiers, so that the maximum gain below oscillation can be used in a large-scale network
Fibre Brillouin amplifiers are of particular interest for very long distance fibre links. These distributed
amplifiers are based on Brillouin scattering, i.e. the coherent build-up of a phonon wave, that by scattering
light from an optical pump coherently amplifies an incoming optical signal. Such fibre Brillouin amplifiersfeature narrow gain bandwidths of ~10 MHz 454. This allows for an efficient distinction between the two
directions of the signal in a bi-directional fibre link, which typically are coded by frequency shifts of several
tens of Megahertz. Compared to bi-directional EDFAs, such narrow-band amplifiers can operate at a muchhigher gain. For fibre Brillouin amplifiers located in a laboratory, a small-signal gain in excess of 50 dB has
been demonstrated455. As this allows for larger distances between the amplifiers, the deployment of fibre
Brillouin amplifiers is expected to substantially decrease the complexity of long-distance fibre links. We now
report on progress in developing autonomous fibre Brillouin tracking amplifiers (FBTA). In a first field test,
a FBTA module was placed in a remote container located at a distance of around 160 km (length of fibre)
from the signal source. We achieved automated locking of the FBTA to an incoming signal of less than 100
nW, and observed an amplification of around 40 dB.
This work was supported by the European Metrology Research Programme EMRP under SIB-02 NEAT-FT. The EMRP is jointly fundedby the EMRP participating countries within EURAMET and the European Union.

452

O. Lopez et al., Appl. Phys. B, DOI 10.1007/s00340-012-5241-0, 2012, and refs. therein453

K. Predehl et al., Science, vol. 336, p. 441-444, 2012.

454

F. Rohde, E. Benkler, and H. R. Telle, Opt. Lett., vol. 38, p. 103-105, 2013, and refs. therein455

O. Terra, G. Grosche, and H. Schnatz, Opt. Expr., vol. 18, p. 16102-16111, 2010.

IFCS-EFTF5-PCD5-27

Tracking DDS for Coherent Optical Links
C. E. Calosso1, E. K. Bertacco1, D. Calonico1, C. Clivati1,2, G. A. Costanzo1,2, F. Levi1, S. Micalizio1, A.
Mura1
1

Optic Division, INRIM, Torino, Italy.
2
Politecnico di Torino, Torino, Italy
Email: c.calosso@inrim.it

Frequency transfer via optical fiber is a mature technology that allows coherent frequency dissemination
over hundreds of kilometers with a residual uncertainty in the 10-19 range456,457. The electronics involved
is well established and is based on a frequency mixer as phase comparator, joined with a frequency
divider to extend its phase input range and a tracking oscillator or a quartz filter to clean up the beat noteof the local laser with the round trip one. In addition two frequencymeters or phasemeters are needed tomeasure the correction applied to the fiber and to monitor the link performance.
Here we propose an alternative digital solution that integrates the whole electronics: compensation andmonitoring of the fiber link, comprehensive of phasemeters, into a single board based on three Direct
Digital Synthesizers (DDS) driven by one Field Programmable Gate Array (FPGA).
Two DDSs are used to track the phase of the two beat notes (the one that measures the fiber delay andthe one that monitors the link) while the third one is used to compensate for the fiber fluctuations byacting on a Acousto Optic Modulator (AOM). The FPGA drives the three DDSs, calculates thecorrection and interfaces a PC to set the working parameters and to monitor the internal signals, inparticular the correction to the fiber and the link performance.
This system is compact, flexible and cost effective and, at the same time, it allows a completecharacterization of the link.
At the conference we will present the electronics in details, comparing the present architecture with theone commonly used.
Furthermore, we will show the experimental tests performed in laboratory environment (up to 100 km
dark fiber link) and on a real coherent optical link (47 km, DWDM architecture with coexisting data
traffic).

456

K. Predehl, G. Grosche, S. M. F. Raupach, S. Droste, O. Terra, J. Alnis, Th. Legero,T. W. Hansch, Th. Udem, R.
Holzwarth, H. Schnatz, “A 920-Kilometer Optical Fiber Link for Frequency Metrology at the 19th decimal place,” Science
336, 441-444 (2012).
457

O. Lopez, A. Haboucha, F. Kefelian, H. Jiang, B. Chanteau, V. Roncin, C. Chardonnet, A. Amy-Klein, G. Santarelli,“Cascaded multiplexed optical link on a telecommunication network for frequency dissemination,” Opt. Expr.
18, 16849-16857 (2010).

IFCS-EFTF5-PCD5-28

Simultaneous Transmission of Time and Frequency
Signals over Optical Fibers
Yang Fei, Gui Youzhen, Cai Haiwen, Han Chunhao, Cai Zhiwu
Shanghai Key Laboratory of All Solid-State Laser and Applied Techniques,Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai,
China
Email: yzgui@siom.ac.cn
In this report, we realized the simultaneous transmission of time and frequency signals over opticalfibers based on wavelength division multiplexer (WDM) and two way optical compensation techniques.
Firstly the fiber link was stabilized by frequency signal propagation errors. Once the fiber link isstabilized, any signal transfer in the link would be stabilized. Then the fluctuations of the frequency andtime signal are compensated simultaneously. On the other hand, for being not affected by each other, thetime and frequency signals would be modulated independently on different wavelength lasers, thenaccess the stabilized fiber link making use of WDM.
We transfer the 1 pps time signal andthe 100 MHz frequency signal over
80 km optical fiber spool inlaboratory. And the spool iscomposed of 6 fiber spools withlength of 1 km, 2 km, 2 km, 25 km,
25km and 25 km. They are joinedwith FC/UPC connector in order tosimulate the loss and reflection of thecommercial optical fiber network.
The schematic of the system isshown in Fig.1.

Temperature controlled
fiber delay line / 10 km

WDM 1

DFB laser λ2

EOM 1

DFB laser λ1

EOM 2

Fiber spool/ 1 km

OpticalfilterSplitter
1pps squaretime reference

×Reference
generator
100MHz sine
frequency reference

Fiber spool/ 2 kmPolarization
scramberFiber spool/ 2 kmSplitter
DFB laser λ3

Low pass filter

EOM 3

×

Polarization
scramberPhase analysis

TIC

FC/UPC
connector

PID

PD 3

Splitter
Splitter
1pps
OutputPD 2
PD 1

100MHzOutput

WDM 2

Fiber spool/ 25 kmFiber spool/ 25 kmFiber spool/ 25 kmRemoteFig. 149: Schematic of the time and frequency transfer system

In the un-compensated case, thebased on WDM and two way optical compensation.
Allan deviation of the fractionalfrequency stabilities of the 100 MHz in the whole 80 km link, the root mean square (RMS) and peakpeak fluctuated values of the propagation delay of the 1 pps signal between the local and remote end are
8.3×10-14 @ 104 s, 2529 ps @ 11 hour, and 12400 ps @ 11 hour respectively. And they are 2×10-17 @ 104
s, 59 ps @ 13 hour, 398 ps @ 13 hour in the compensated case.
Meantime, we found the fluctuation of pps signal induced by the electro-optical modulation may be alittle high. But the fluctuation could be reduced by increasing frequency and averaging. We made the 1pps signal to trigger a function generator. And it generated an output pulse signal with a rate of 100 Hz.
The time interval counter (TIC) gave the propagation delay time of the pulse signal between the local
and remote end averaged over every 100 measurement samples. In the condition, the RMS and peakpeak values of the output data are 11 ps @ 12 hour and 59 ps @ 12 hour respectively.

IFCS-EFTF5-PCD5-29

Distributed Time Transfer Using Optical Fiber Links
Liang Hu, Guiling Wu, Jianguo Shen, Huang Huang, Jianping Chen
State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong
University, Shanghai 200240, China
Email: wuguiling@sjtu.edu.cn
Time transfer over optical fiber links458 has attracted extensively interests due to its advantages of broad
bandwidth, low loss and so on. In this paper, we propose a one point to multi-points distributed timetransfer scheme using optical fiber links. A 1 to 8 experimental system over 20km single-mode fiberwith stabilities less than 50ps is demonstrated.
The experimental setup of the
proposed scheme is shown in Fig.1.
The system consists of a master
node, a 1 to 8 optical splitter and 8
slave nodes. The length of the
optical fiber between the master andeach slave is 20 km. The slaves areaccessed to the master by using thetime division multiple accessmechanism. The bidirectional fiber
path between the master and eachslave is built under the control of themaster by designating time slot for
Fig. 1: the setup of the propose distributed time transfer
each slave in a certain sequence.
Time at master is transferred to eachslave over the corresponding bidirectional fiber
path by the two-way time transfer method duringassigned time slots.
Fig.2 shows the measured time differences
between the master and two slaves and their
RMS in each time slot of 1 hour within 21 hours
measurement. We can see that the system can
implement distributed time transfer successfully
and reach stabilities less than 50ps in each time
slot.

Fig. 2: the measured time difference and RMS

458

A. Imaoka and M. Kihara, “Accurate time/frequency transfer method using bidirectional WDM transmission,” IEEE trans.
On Instrumentation and Measurement, Vol.47,No.2, pp.537-542, 1998.

IFCS-EFTF5-PCD5-30

Compass Receiver Positioning Algorithm under Bad conditions
Based on Unequal Interval Clock Prediction
Jianwei Zhan1, Peng Wu1, Hang Gong1, Guozhu Zhang1, Gang Ou1
1

School of Electronic Science and Engineering, National University of Defense Technology, Changsha,
Hunan 410073, China

Email: sophy_zjw@nudt.edu.cn
It is widely known that at least four code pseudorange measurements are required before a position canbe determined. However, positioning service is untermittent in the area where the satellite visibility islimited or the satellite signal is weak due to the blockage or signal jamming, such as in the undergroundtraffic rountes, the tunnels, and park garages.
To solve this problem, a positioning method based on the unequal interval series of receiver clock bias isutilized to augment COMPASS receiver. The current researches do not refer the prediction model basedon the unequal interval data. The conventional grey model in previous studies is based on the equalinterval data. In this paper, an improved prediction grey model is proposed, which adopts a time interval
coeffident and the TDOP coeffident to generate the difference clock series. And then a predicted clock
value from the proposed model is introduced to aid positioning.
Actual test data were used to verify the methods which are under unequal and equal conditions
respectively．Experimental test results with COMPASS data demonstrate that the prediction model inthis paper is more suitable for predicting receiver clock bias，and the proposed positioning method can
implement a good estimation of three-dimensional position when only three satellites are available．

IFCS-EFTF Group 6 poster session 2
Forum Hall
Wednesday & Thursday, July 24-25, 2013, 1:00 pm - 2:00 pm and 3:30 pm - 4:30 pm
Chair:

Sébastien BizeSYRTE-Observatoire de ParisIFCS-EFTF6-PCD6-1

Development of Optical Frequency Standard based on 87Sr
Sergey Slyusarev1, Ksenia Khabarova1, Alexey Kostin1,
Sergey Strelkin1, Gleb Belotelov1, Vitaliy Pal’chikov1, Nikolay Kolachevsky2
1

FSUE “VNIIFTRI”, Mendeleevo, Russia
2
LPI RAS, Moscow, Russia
Email: vitpal@mail.ru

In the present work we discuss the experiment on creating frequency standard based on the clocktransition 1S0 – 3P0 at λ0 = 698 nm in 87Sr atoms, trapped in a 1D vertical optical lattice.
The first stage of atoms cooling and trapping was realized using the Zeeman slower and a “blue”
magneto-optical trap on 1S0 — 1P1 transition (λ = 461 nm), with 496 nm and 679 nm repumping lasers.
For the second stage, a laser system with a narrow generation line has been developed and investigated.
A 689-nm semiconductor laser has been stabilised using an external reference ultrastable cavity withvibrational and temperature compensation near the critical point. The lasing spectral width was 80 Hz(averaging time 40 ms), and the frequency drift was at a level of 0.3 Hz s-1. Comparison of two
independent laser systems yielded a minimum Allan deviation: 2 × 10-14 for 300-s averaging. It is shownthat this system satisfies all requirements necessary for secondary cooling of 87Sr atoms using thespectrally narrow 1S0 — 3P1 transition (λ = 689 nm).

(a)

(b)

Fig. 150: (a) The beating spectrum of two identical lasers, locked to ULE1 and ULE2 resonators (14 data sets weretaken each with the resolution 47 Hz in 40-μs time, and then averaged). (b) Allan deviation of the beating signal,
while subtracting linear drift (curve 1) and without subtracting it (curve 2).

IFCS-EFTF6-PCD6-2

Development of a Moving system for cavity-build-up Lattice
Chang Yong Park, Dai-Hyuk Yu, Won-Kyu Lee, Sangkyung Lee, Sang Eon Park,
Sang-Bum Lee, Jongchul Mun, Myoung-Sun Heo, and Taeg Yong Kwon
Division of Physical Metrology, Korea Research Institute of Standards and Science,
Daejeon 305-340, Korea
Email: cypark@kriss.re.kr
A moving system of cavity build-up lattice will be developed for an Yb optical lattice clock at Korea
Research Institute of Standards and Science (KRISS). As the accuracy of optical clock has been
improved, the black body radiation (BBR) shift becomes a major part of total uncertainty. The static anddynamic polarizability of Yb atoms was measured with 10 -5 accuracy recently by the research group of
NIST. To exploit the accuracy of the polarizability fully, a well-prepared black body condition is needed
for the spectroscopy chamber like a cavity wherein trapped atoms are transferred by a moving lattice.
Usually such a moving lattice can be formed by interference between counter-propagating two lasers
with frequency offset to each other. However, in this way only the half of the potential depth is obtained,
compared with the one obtained by normal way of using a reflection mirror for a counter propagating
laser. Considering the temperature (10~20 K) of cooled Yb atoms by inter-combination transition,
obtaining a laser source for lattice with enough power is problematic. Our solution is to use cavitybuild-up lattice and to move the whole build- up cavity system. We will design an optical cavity withenhancement factor of ~50 traveling vertically between magneto-optical trap region and thespectroscopy chamber. The advantage of this way is that atoms are always located in the beam waist of
the lattice laser beam as is pointed out by other group459 of PTB who already has built the lattice onmoving stage. In our system, because of the cavity resonant condition the two cavity mirrors aremounted on one body moving stage, so that the separation of two mirrors preserves constant with lesseffort. By using fast PZT mounting a cavity mirror, the residual vibration will be compensated.
Optionally depending on the performance of the feedback control on the PZT, we expect to increase theenhancement factor of the cavity, from which we can obtain the higher leverage effect in evaluation of
hyper-polarizability shift or larger volume of an each site of optical lattice to reduce the collisional shift.
In this presentation we will describe details of our moving lattice system and experimental results.

Fig.1 The proposed moving system of cavity-build-up lattice.
Two curvature mirrors will be aligned vertically on a moving
stage. Black body chamber is located 2 cm above the center ofthe magneto optical trap. A vacuum chamber with 18 viewports
will be designed compactly to reduce the mass of moving stage.

459

Thomas Middelmann, et al., “Long-range transport of ultracold atoms in a far-detuned one-dimensional optical lattice”,
New J. Phys. 14, 073020 (2012)

IFCS-EFTF6-PCD6-3

Project of photoassociation measurments for determination of thedensity shift of 1S0-3P0 clock transition in neutral strontium
Marcin Bober1, Piotr Morzyński1, Michał Zawada1, Piotr Wcisło1, Agata Cygan1, Daniel Lisak1, Roman
Ciuryło1, Jerzy Zachorowski2, and Wojciech Gawlik2
1

2

Institute of Physics, Nicolaus Copernicus University, Torun, Poland
M. Smoluchowski Institute of Physics, Jagiellonian University, Cracow, Poland
Email: bober@fizyka.umk.pl

Recent progress in optical atomic clocks with neutral strontium atoms in an optical lattice allows to
reduce uncertainty to 10-16 level460. Important contribution to accuracy budget came from cold atoms
collisions in the lattice. In this work we report apparatus for determination of scattering properties of 3P0
state in strontium.
We plan to make direct measurement with the clock transition (698 nm) or to use a three photons
photoassociation using 689, 679 and 707 nm lasers. This measurement will be performed with themagneto-optical trap setup461 designed for experiments with both 88Sr and 87Sr isotopes. At the sametime we are preparing the second setup, exclusively designed as the optical lattice atomic clock withstrontium atoms. With those two strontium systems we plan to study the density shift of 1S0-3P0 clocktransition in strontium.

460
461

R. Le Targat et al. “Experimenting an optical second with strontium lattice clocks”, arXiv:1301.6046

M. Bober et al. “Precision spectroscopy of cold strontium atoms, towards optical atomic clock”, Bull. Pol. Ac.:
Tech., 60(4), 707, 2012

IFCS-EFTF6-PCD6-4

Strontium Optical Lattice Clock Research at NIM
Yige Lin1, Qiang Wang1,2, Ye li1,2, Shaokai Wang1, Fei Meng1, Baike Lin1, Yang Zhao1,2, Shiying Cao1,
Minming Wang1, Jianping Cao1, Erjun Zang1, Tianchu Li1, Zhanjun Fang1
1
2

Division of Time and Frequency Metrology, National Institute of Metrology, Beijing, China
Department of Precision Instruments and Mechanology, Tsinghua University, Beijing, China
Email: linyige@nim.ac.cn

A strontium lattice clock is being built at NIM. Our experiments started with laser cooling and trappingof 88Sr. The atoms are cooled by two-stage laser cooling. After the first stage laser cooling on 1S0-1P1transition with a commercial 461 nm laser, about 108 88Sr atoms are cooled to 3 mK. The second stage
cooling laser system has a master-slave configuration. The master laser is an external cavity diode laser(ECDL) which is lock to a reference cavity (finesse is ~ 10000). The linewidth of the master laser isreduced to 150 Hz by locking to the reference cavity with Pound-Drever-Hall technique. The slave laser
is injection locked to the master laser. With this narrow 689 nm laser system, the 88Sr atoms could becooled to as low as 3 μK via 1S0-3P1 transition. The horizontally oriented optical lattice is formed by an
813 nm Tapered-Amplifier laser with trap depth of 32 μK.
The 698 nm clock laser is an ECDL locked to ahigh finesse cavity (finesse is ~ 200,000). The
support points of the cavity are optimized byfinite element analysis. The beat of two similarsystems show a linewidth of ~5 Hz, and the Allan
deviation is ~ 3e-15 @ 1 s.
Magnetic field induced spectroscopy is introduced
to make the single photon 1S0-3P0 transition
possible in 88Sr.462 The sideband resolved
spectrum is obtained by logging the transition
probabilities when scanning the probe laser
frequency, and is shown in fig.1(a). The trapping
sidebands are ~ 100 kHz away from the carrier.
The fit to the blue detuned sideband shows thatthe temperature of the atom in the lattice is ~ 7
μK. The Narrowest transition we got is ~ 100 Hz.
The experiment was then transferred to 87Sr. The
87
Sr atoms have been loaded into the opticallattice and the sideband resolved spectrum isobtained as shown in fig.1(b). We are now trying
to compensate the earth magnetic field to narrow
down the transition linewidth and make apreliminary lock to the atomic transition.
Fig. 151: sideband resolved spectroscopy ofStrontium

462

Y.G. Lin, Q. Wang, Y. Li et al. “Magnetic Field Induced Spectroscopy of 88Sr Atoms Probed with a 10 Hz Linewidth
Laser,” Chin. Phys. Lett., vol. 30, no. 1, p. 014206, 2013.

IFCS-EFTF6-PCD6-5

Compact Atomics Package for a Transportable Strontium
Lattice Clock
Yeshpal Singh, Lyndsie Smith, Ole Kock, Wei He, Huadong Cheng, Kai Bongs and the SOC2 team2
1

Department of Physics and Astronomy, University of Birmingham, Edgbaston Park Road, Birmingham
B15 2TT, UK
2
Heinrich- Heine-Universität Düsseldorf, Germany
Physikalisch-Technische-Bundesanstalt,Germany
Leibniz Universität Hannover, Germany
Observatoire de Paris, France; Universita’ di Firenze,
National Physical Laboratory Teddington, the United Kingdom
TOPTICA Photonics AG, Germany; EADS Astrium Friedrichshafen, Germany
Menlo Systems GmbH, Germany; Kayser-Threde GmbH, Germany; Kayser Italia S.r.l.,Italy
Centre Suisse d’Electronique et de Microtechnique SA, Switzerland ; Université deNeuchâtel, Switzerland ; Ecoles Polytechniques Fédérales Lausanne,
Switzerland
Istituto Nazionale di Ricerca Metrologica, Italy

Email: y.singh.1@bham.ac.uk
With the rapidly improving performance of optical clocks, in the future, most applications requiring thehighest accuracy will require these systems. The unprecedented accuracy in time promises new
applications like relativistic geodesy which might benefit the
exploration of oil and minerals, fundamental tests of generalrelativity and synchronization for long base line astronomicalinterferometry, deep space navigation. In the framework of
the research project SOC2:“Towards Neutral-atom Space
Optical Clocks” funded by the EU 7th framework programme(FP7/2007-2013) under grant agreement n. 263500, with themain aim of developing demonstrators of transportable latticeclocks with 5x10-17 relative frequency accuracy [1], we arereporting on the concept of a very compact, light and energy
efficient atomics package for a Sr clock prototype. At theheart of the atomics package is a 3D MOT chamber (Fig.1)
which can be loaded either with a permanent magnet Zeeman
slower or with a 2D MOT facility. The total budget of thesystem will be <10 l, <10-10 mbar, < 20 kg [2].
Fig. 152: Design of the 3D MOT
References:[1] S. Schiller et al. “Towards Neutral-atom Space Optical chamber.
Clocks (SOC2): Development of high-performancetransportable and breadboard optical clocks and advanced subsystems” on “Let’s embrace space, volume
II” 45, 452-463 (2012). ISBN 978-92-79-22207-8.
[2] www.soc2.eu

IFCS-EFTF6-PCD6-6

A ground based Yb lattice clock to participate in future
space-clock missions: commencement
J.J, McFerran1, N. Kostylev1, E. Ivanov1, J.G. Hartnett2, A.N. Luiten2 and M. Tobar1
1School of Physics, University of Western Australia, Australia
2
IPAS, University of Adelaide
Email: john.mcferran@uwa.edu.au

Recent measurements in various laboratories have shown astonishingly high accuracy for a number ofdifferent clock transition frequencies and ratios [1-7]. However, these clocks are isolated in separate laboratories
around the globe, which limits the degree of confirmation. With future space-clock missions such as the Atomic
Clock Ensemble in Space (ACES) mission and possible future missions, such as Space Optical Clock (SOC) andSTE-QUEST, a much greater opportunity will be granted for frequency comparisons between clocks distributed
around the earth.
While optical fibre links can permit ultra-stable clock comparisons over many hundreds of kilometers [8],they cannot be used for clocks as isolated as; for example, Perth Western Australia. At UWA we are developing a
Yb based 1-dimensional optical lattice clock with the aim of participating in future space-clock missions. Similar
171
Yb, (6s2) 1S0 -- (6s6p) 3P0, based clocks have been developed before [2,9,10] and the transition is included in
the CIPM’s list of secondary representations of the second. In this poster presentation we outline the details of
the clock design. To maximize the number of atoms available for probing we will use a Zeeman slower and twostages of cooling in a magneto-optical trap, before loading into a lattice trap. The main chamber is to be compact
for easier current control and to minimize thermal gradients. Having a compact chamber and multiple stages oflaser cooling presents a challenge. We will illustrate a scheme that addresses this issue and present somepreliminary results in relation to the Yb oven and laser systems.

[1] N. Huntemann, M. Okhapkin, B. Lipphardt, S. Weyers, C. Tamm, and E. Peik , Phys. Rev. Lett. 108,090801 (2012).
[2] C.W. Chou, D. B. Hume, J. C. J. Koelemeij, D. J. Wineland, and T. Rosenband, Phys. Rev. Lett.
104, 070802 (2010).
[3] N. D. Lemke, A. D.Ludlow,Z.W.Barber,T. M.Fortier, S. A. Diddams, Y. Jiang, S.R. Jefferts, T. P.
Heavner, T. E. Parker, and C.W. Oates, Phys. Rev. Lett. 103, 063001 (2009).
[4] T. Rosenband, D. Hume, P. Schmidt, et al., Science 319, 1808 (2008).
[5] A. Ludlow, T. Zelevinsky, G. Campbell, et al., Science 319, 1805 (2008).
[6] J.J. McFerran, L. Yi, S. Mejri, S. Di Manno, W Zhang, J. Guéna, Y. L. Coq, and S. Bize, Phys.
Rev. Lett. 108, 1830041 (2012).
[7] A.A. Madej, P. Dubé, Z. Zhou, J.E. Bernard, and M. Gertsvolf, Phys. Rev. Lett. 109, 203002(2012).
[8] K. Predehl, G. Grosche, S. M. F. Raupach, S. Droste, O. Terra, J. Alnis, Th. Legero, T. W. Haensch,
Th. Udem, R. Holzwarth, and H. Schnatz.. Science, 336, 441 (2012).
[9] T. Kohno, M. Yasuda, K. Hosaka, H. Inaba, Y. Nakajima, F-L Hong, Appl. Phys. Exp. 2, 072501(2009)[10] C.Y. Park, D.-H. Yu, W.-K. Lee, S.E. Park, E.B. Kim, S.K. Lee, J.W. Cho, T.H. Yoon, J. Mun, S.J.
Park, T.Y. Kwon, S.-B. Lee, Metrologia, 50, 119 (2013).

IFCS-EFTF6-PCD6-7

Ion trap heating – measurement and model
Petr Balling1, Miroslav Doležal1, Hugh Klein2, Steven King2, Patrick Gill2, Thomas Lindvall3, Anders
Wallin3, Mikko Merimaa3, Christian Tamm4, Piet O. Schmidt4, Tanja E. Mehlstäubler4, Ekkehard Peik4
1

Czech Metrology Institute, Prague, Czech Republic
National Physical Laboratory, Teddington, United Kingdom
3
Centre for Metrology and Accreditation (MIKES), Espoo, Finland
2

4

Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany

Email: pballing@cmi.cz
Blackbody radiation-induced shifts make a significant contribution to the uncertainty budget of trapped
ion optical clocks463. One of the tasks of EMRP project SIB04 Ion Clock is the development of aquantitative model of the thermal environment seen by the ion. FEM models, including skin effect andRF losses in dielectrics, were created using ANSYS/HFSS software for ion traps used by project
partners. The models are being refined and verified using the temperature measurements of “dummy”
traps; critical parts and parameters will be identified for optimization of the future trap designs.
Thermal imaging measurements of the traps involve calibration of both an infrared camera (FLIR A615)
working in the 7 to 14 μm range and the transmission of an AR coated ZnS window. The emissivity ofmaterials used (tantalum, molybdenum, titanium, macor, alumina, sapphire etc.) was estimated bycomparison with a near-perfect black emitter at several known temperatures in vacuum. The results wereused to correct the raw thermal image data. However they cannot be directly used to estimate the total
emitted radiation in the case of spectrally dependent samples like sapphire. Preliminary measurements
and simulations of an NPL end-cap trap are shown below. More details and other examples will bepresented at the joint symposium.
25.0
24.5

Bottomelectrode24.0

temperature [°C]

23.5
23.0

22.5
22.0

Chamber & ref.
black emitter at thesame temperature

21.5

21.0

RF off

RF on

20.5
20.0
0:00

0:15

0:30

0:45

1:00 1:15
time [h:mm]

1:30

1:45

2:00

2:15

2:30

Radiometric measurement of various locations on the NPL
end-cap dummy trap parts corrected for reflected radiation,
window transmission and emissivity.

FEM results - steady state surface temperature

Discussion with consortium members is gratefully acknowledged. The EMRP is jointly funded by the
EMRP participating countries within EURAMET and the European Union.

463

Mitroy, J, et al. "Theory and applications of atomic and ionic polarizabilities." J. Phys. B: At. Mol. Opt. Phys. 43 (2010)
202001.

IFCS-EFTF6-PCD6-8

Design and construction of helical resonators for ion traps
Ke Deng, Yunlong Sun, Jie Zhang, Zehuang Lu, and Jun Luo
MOE Key Laboratory of Fundamental Quantities Measurement, School of Physics,
Huazhong University of Science and Technology, Wuhan, P.R. China
Email: zehuanglu@mail.hust.edu.cn
Single trapped ions are recognized as important candidates for realizing optical frequency standards. To
drive the ion trap, a high-Q resonator is needed, and a predictable high driving frequency is generally
preferred. Usually the high-Q resonator is realized through a helical resonator. The resonant frequency
of a helical resonator without load can achieve rather large resonant frequency (50~60 MHz), which canbe calculated by empirical formula. However, when the resonator is connected to the ion trap, theresonant frequency will be reduced substantially464 due to the parallel capacitive impedance of the trap
and feed-through. Less effort has been made on how to predict the resonant frequency when theresonator is attached to the trap electrodes.
In this paper we will model the resonator with a lumped element electrical equivalent model and predictthe resonant frequency under the realistic condition when the helical resonator is connected to an ion
trap. Based on our model, we construct a resonator and Fig. 1 shows a picture of the constructed helicalresonator. Inside diameter of the shield of the resonator is 100 mm. The turn and direction of the antennacoil is adjusted to make it match 50 Ohm impedance. In order to maintain the winding pitch and thediameter of the main coil to be constant, we use a lathe and a tube to wind the coil instead of by hand.
The unloaded Q-factor of the resonator is about 300. We measure the resonant frequencies under
different loads. The experimental results concur with our prediction.
To test the practical performance of the resonator, we use it to drive a linear Paul trap. After
optimization, the Q-factor of the resonator is still about 300 after the trap is connected. The trap
electrodes are driven at 25 MHz. We trap 24Mg+ by this resonator. Pictures of 24Mg+ are recorded by an
EMCCD camera. The result is shown in Fig. 2.

Fig. 1: Picture of the helical coil resonator464

Fig. 2: Pictures of crystallized 24Mg+

J. D. Siverns, L. R. Simkins, S. Weidt, and W. K. Hensinger, “On the application of radio frequency voltages to ion traps
via helical resonators”, Appl. Phys. B, vol. 106, p. 327-338, 2012.

IFCS-EFTF6-PCD6-9

Incoherent Repumper and Clearout Light Sources for Sr + Ion
Traps
Thomas Fordell, Thomas Lindvall, Tuomas Hieta, Mikko MerimaaCentre for Metrology and Accreditation (MIKES), Espoo, Finland
Email: thomas.fordell@mikes.fi

In addition to the extremely stable clock laser, an optical clock requires several other light sources thatmust resonate with electronic transitions in the reference ion or atoms. If lasers are used, wavelengthstabilization is required, which is usually a delicate process that calls for continuous operation of thelasers. If the requirement of frequency stabilization can be relaxed, a simplification of the light source
ensemble results, which is a highly desirable feature particularly in transportable clocks and spaceclocks.
In a recent paper465, the use of incoherent, unpolarized repumper and clearout light sources based on
amplified spontaneous emission (ASE) was proposed. An unpolarized ASE source is broadband and assuch requires no frequency stabilization. Moreover, in the case of the repumper, such a source requires
no external polarization modulation to prevent dark states even in a zero magnetic field. It can also drive
multiple hyperfine transitions simultaneously. In a Sr+ single-ion clock, efficient cooling and detection
requires a power spectral density (PSD) on the order of 1 mW/nm for an ASE repumper. Rapid
emptying of the metastable clock state requires a PSD about an order of magnitude less for the clearout
light source.
In this contribution we present prototype fibre
optic light sources that meet these requirements.
Both repumper and clearout sources are based on
Yb-doped fibre, a 980 nm semiconductor pumplaser and standard fibre optic components, suchas fibre Bragg gratings, fused splitters,
wavelength division multiplexers and isolators.
The all fibre approach ensures adjustment free
operation. Moreover, since no frequency
stabilization is needed, the sources can beswitched on and off electronically during theclock cycle simply by modulating the pump laser
current. For the repumper the turn-on time is a
few milliseconds, the turn-off time somewhat
longer: about 10 ms to reach the 10-7 level that isneeded for the light shift of the clock transition
to be less than 10-17 at the start of the clockinterrogation cycle.

465

Fig. 153: PSD of the prototype ASE repumper. The
spectrum has been engineered to be very low at 1033
nm in order for the repumper not to prevent thedetection of clock transitions.

Lindvall et al., ”Unpolarized, incoherent repumping light for prevention of dark states in a trapped and laser-cooled singleion”, Phys. Rev. A, vol. 87, 013439, 2013

IFCS-EFTF6-PCD6-10

Dark-State Suppression in a Trapped and Laser-Cooled
Alkaline-Earth-Metal Single Ion
Thomas Lindvall1, Thomas Fordell1, Alan A. Madej2, Ilkka Tittonen3, Mikko Merimaa1
1

2

Centre for Metrology and Accreditation (MIKES), Espoo, Finland
Frequency and Time Group, National Research Council of Canada, Ottawa, Canada
3
Department of Micro- and Nanosciences, Aalto University, Espoo, Finland
Email: thomas.lindvall@mikes.fi

We study dark states in a single laser-cooled alkaline-earth-metal ion in a radiofrequency trap. Both
Doppler cooling and fluorescence detection of the ion rely on obtaining a high scattering rate on the2
S1/2-2P1/2 transition. However, many commonly used ion species have a low-lying metastable 2D3/2 statethat can become populated due to spontaneous emission from the 2P1/2 excited state. This requires a
repumper laser to maintain the ion in the cooling cycle. The 2D3/2-2P1/2 repumper transition has darkstates for any laser polarization. These can be destabilized by an external magnetic field or bymodulating the polarization, for example, using an electro-optic modulator466. Using 88Sr+ as an
example, we study the different types of dark states that can occur and how to prevent them in order to
optimize the laser cooling and the scattering rate. The calculations are compared to experimental results
obtained at the National Research Council of Canada and are found to be in good agreement (see Fig. 1).
Recently we proposed using unpolarized, incoherent amplified spontaneous emission (ASE) to drive therepumping transition467. The ASE repumper offers several advantages compared to a laser repumper. It
prevents dark states without polarization modulation using a single beam even in the near-zero magnetic
field required for an ion clock. Due to its broad bandwidth, it requires no frequency stabilization. In
addition, the source can be switched on and off electronically simply by modulating the pump laser
current. These features, and the fact that the ASE source is fiber based, make it very compact and robust,which is essential for thedevelopment of practical,
transportable
opticalclocks.
This work was funded by
the Academy of Finland(project 138894). TF
acknowledges financial
supportfromtheEuropeanCommission(Marie Curie Integration
Grant PCIG10-GA-2011Fig. 154: (a) Measured and (b) calculated single-ion fluorescence spectra as a304084).
function of cooling laser detuning for increasing Rabi frequencies (bottom totop). The repumper was red-detuned to make the coherence dips visible.

466

T. Lindvall, M. Merimaa, I. Tittonen, and A. A. Madej, “Dark-state suppression and optimization of laser cooling andfluorescence in a trapped alkaline-earth-metal single ion”, Phys. Rev. A 86, 033403 (2012).
467

T. Lindvall, T. Fordell, I. Tittonen, and M. Merimaa, “Unpolarized, incoherent repumping light for prevention of darkstates in a trapped and laser-cooled single ion”, Phys. Rev. A 87, 013439 (2013).

IFCS-EFTF6-PCD6-11

On the Interpolation Between
Optical Frequency Standards and Primary Clocks
by Use of Ultrastable Resonators
Fritz Riehle, Uwe Sterr, Christian Hagemann, Christian Grebing
Physikalisch-Technische Bundesanstalt (PTB), 38116 Braunschweig, Germany
Email: Uwe.Sterr@ptb.de
The frequency instability of state-of-the art primary caesium fountain clocks is ultimately limited to thequantum projection noise determined by the line quality factor of the caesium transition and the numberof the atoms in the fountain to 4 × 10-14 (τ/s)-1/2 at best468. For typical operation of the best clocks theinstability is higher by up to almost an order of magnitude as a result of limitations due to a reduced
number of atoms usually employed to reduce systematic shifts or the Dick effect469 of the interrogating
oscillator.
On the other hand, optical frequency standards have already shown fractional instabilities as low as 5 ×
10-16 (τ/s)-1/2 with the prospects to come down to the 10-17 regime470. So even with the very best caesium
clocks the measurement of an optical frequency with a fractional uncertainty of 10-16 will range fromseveral days to more than a month. Not many optical clocks have proven such a long operation time.
To bridge this gap of instability and allow for regular comparisons of cesium clocks to optical clocks attheir best performance we propose the use of an ultrastable optical resonator like a silicon resonator at
cryogenic temperature471 to interpolate between relatively short averaging intervals with respect tooptical clocks and the long intervals required to reach the accuracy of the primary standards. A laser
stabilized to such a resonator has shown a fractional instability near or below 1× 10-16 for interrogation
times near 1 s with very small drifts on longer time scales. However, even these small varying drifts
might limit the practical interpolation time.
We have investigated strategies to mitigate these limitations by measuring the resonator drift against the
optical frequency standards to determine suitable intervals and to correct the frequency comparison
between both clocks accordingly. We present a mathematical treatment of the interpolation method andcompare it to available data from the systems at PTB. Applications of this concept as well as
extrapolations to future standards and resonators will be discussed.
This work was supported by Deutsche Forschungsgemeinschaft DFG in the Centre of Quantum
Engineering and Space-Time Research (QUEST) of the Leibniz Universität Hannover and the EMRP
IND14. The EMRP is jointly funded by the EMRP participating countries within EURAMET and theEuropean Union.

468

G. Santarelli, P. Laurent, P. Lemonde, A. Clairon, A. G. Mann, S. Chang, A. N. Luiten, and C. Salomon, Phys. Rev. Lett.
82, 4619 (1999).
469

C. A. Greenhall and G. J. Dick, IEEE Trans. Ultrason. Ferroelec. Freq. Contr. 47, 1593 (2000).

470

Y. Y. Jiang, A. D. Ludlow, N. D. Lemke, R. W. Fox, J. A. Sherman, L.-S. Ma, and C. W. Oates, Nature Photonics 5, 158(2011).
471

T. Kessler, C. Hagemann, C. Grebing, T. Legero, U. Sterr, F. Riehle, M. J. Martin, L. Chen, and J. Ye, Nature Photonics
6, 687 (2012).

IFCS-EFTF6-PCD6-12

Nd:YAG lasers with a most probable linewidth of 0.6 Hz
H. Q. Chen1, Y. Y. Jiang1, S. Fang1, Z. Y. Bi1, L. S. Ma1
1State Key Laboratory of Precision Spectroscopy, East China Normal University,
3663 N. Zhongshan Road, Shanghai 200062, China
Email: zybi@phy.ecnu.edu.cn

Lasers with ultra-low phase noise and high frequency stability are pursued in many applications, such as
optical atomic clocks, tests of fundamental physics, low-phase-noise microwave generation andgravitational wave detection. Lasers with sub-Hz linewidth can be realized by using the Pound-DreverHall (PDH) technique to stabilize the laser frequency to an external ultra-stable Fabry-Perot reference
cavity1-4. In this work, two independent similar cavity-stabilized Nd:YAG lasers at 1064 nm areconstructed, which can run continuously over three weeks. In each laser system, the reference cavity is
7.75-cm long and is vertically mounted5-8. The cavity has a finesse measured to be ~200,000,
corresponding to a cavity linewidth of <10 kHz. Each cavity is located in a gold-coated copper cylinder
thermal shield, which is enclosed in a vacuum chamber. Both of the vacuum assembles for the reference
cavity and the optic components for the PDH technique are on a passive vibration isolation platform (VIP)for vibration reduction. The VIP resides in a home-made box for acoustic isolation with an attenuation of
more than 20 dB. The temperature inside the box is stabilized. Both of the cavity spacer and mirror
substrates are made of ultra-low-expansion (ULE) glass. Zero-expansion temperatures of the composite
cavities are measured to be ~22.87 oC and ~10.58 oC, respectively. Since the vacuum chambers for thecavities are temperature-controlled by heating, one is maintained at near 22.87 oC with sub-mK instability
and the other is stabilized at ~22.9 oC with mK instability. Light is transferred to the VIP by a single-mode
fiber with fiber noise cancellation. Frequency stabilization is accomplished by controlling a piezoelectrictransducer (PZT) bonded on the monolithic Nd:YAG crystal of the laser to keep the laser frequency on
resonance with the reference cavity. 700 measurements of the beat note between two laser systems taken
in four different days over 79 days show that each laser has achieved a most probable linewidth of 0.6 Hz
and a fractional frequency instability of 1.3×10-15 at an averaging time of 1 to 40s. Systematic evaluationshows the performance of each laser system is close to the cavity thermal noise limit.

1

R. W. P. Drever et al., “Laser phase and frequency stabilization using an optical resonator”, Appl. Phys. B, vol. 31, p. 97105, 1983.

2

B. C. Young et al., “Visible lasers with subhertz linewidths”, Phys. Rev. Lett., vol. 82, p. 3799-3802, 1999.

3

Y. Y. Jiang et al., “Making optical atomic clocks more stable with 10 -16-level laser stabilization”, Nature Photonics, vol. 5,
p. 158-161, 2011.

4

T. L. Nicholson et al., “Comparison of two independent Sr optical clocks with 1×10-17 stability at 103 s”, Phys. Rev. Lett.,
vol. 109, p. 230801, 2012.

5

M. Notcutt et al., “Simple and compact 1-Hz laser system via an improved mounting configuration of a reference cavity”,
Opt. Lett., vol. 30, p. 1815-1817, 2005.

6

A. D. Ludlow et al., “Compact, thermal-noise-limited optical cavity for diode laser stabilization at 1×10 -15”, Opt. Lett., vol.
32, p. 641-643, 2007.

7

J. Alnis et al., “Subhertz linewidth diode lasers by stabilization to vibrationally and thermally compensated ultralowexpansion glass Fabry-Pérot cavities”, Phys. Rev. A, vol. 77, p. 053809, 2008.

8

T. Kessler et al., “A sub-40 mHz-linewidth laser based on a silicon single-crystal optical cavity”, Nature Photonics, vol. 6,
p. 687-692, 2012.

IFCS-EFTF6-PCD6-13

Clock Laser Systems for Yb Optical Lattice Clock at KRISS
Won-Kyu Lee, Chang Yong Park, Dai-Hyuk Yu, Sang Eon Park, Sangkyung Lee,
Sang-Bum Lee, Jongchul Mun, Myoung-Sun Heo, and Taeg Yong Kwon
Division of Physical Metrology, Korea Research Institute of Standards and Science,
Daejeon 305-340, Korea
Email: oneqlee@kriss.re.kr
Two types of yellow lasers at 578 nm were developed for a probe laser of an Yb optical lattice clock at
Korea Research Institute of Standards and Science (KRISS) 472 by using sum-frequency generation(SFG) or second harmonic generation (SHG). In the SFG scheme, the output of an Nd:YAG laser at1319 nm and that of an Yb-doped fiber laser at 1030 nm were passed through a periodically-poledlithium niobate (PPLN) waveguide for SFG at 578 nm with an output power of more than 20 mW. In the
SHG scheme, the output of a high-power external-cavity diode laser at 1156 nm was sent throughanother PPLN waveguide for SHG with an output power of more than 10 mW.
The linewidth of the produced yellow light was narrowed by stabilizing the frequency to a super-cavity
made of ULE glass. The cavity was horizontally mounted at the optimal support points to reduce
vibration sensitivity. Also the cavity was installed in a vacuum chamber, and the temperature of thecavity was stabilized at the value for the zero thermal expansion within 10-mK-level accuracy. Thisvacuum chamber was placed on an active vibration-isolation table. This system was installed in an
acoustic enclosure with a 20-dB isolation to block the acoustic noise.

472

1.0

Beatnote Signal (a.u.)

Fig. 1 shows typical FFT spectrum of the beatnote between the two independent clock laser
systems. Since the full width at half maximum(FWHM) of the beat note was about 5 Hz
(resolution bandwidth; 2 Hz), the linewidth of
one clock laser was estimated to be about 3.5
Hz, assuming similar performance of bothlasers. This FWHM linewidth varied between
2 ~ 10 Hz due to frequency jitters. The
frequency jitter was measured to be about 25
Hz in 10 s. Although currently there is muchroom for improvement of the stability of ourclock laser compared with the state-of-the-art
technology, we expect it is stable enough forthe frequency lock to the clock transition of
the Yb lattice clock.

0.8
0.6

~ 5 Hz
0.4
0.2
0.0
-400

-200

0

200

400

Relative Frequency (Hz)Fig. 1: Typical FFT spectrum of the beat note between
two independent clock laser systems with theresolution bandwidth of 2 Hz, and the acquisition timeof 1 s. The FWHM linewidth was estimated to beabout 3.5 Hz assuming similar performance of bothlasers.

C. Y. Park, et al., “Absolute frequency measurement of 1S0(F = 1/2)–3P0(F = 1/2) transition of 171Yb atoms in a onedimensional optical lattice at KRISS”, Metrologia, vol. 50, p. 119-128, 2013.

IFCS-EFTF6-PCD6-14

Determination of Mode Number Using Two Laser Combs with
Large Difference in Repetition Rate
Jin-Long Peng, Tze-An Liu, and Ren-Huei Shu
Center for Measurement Standards, Industrial Technology Research Institute, Hsinchu, Taiwan
Email: jlpeng@itri.org.tw
To measure the frequency of a laser under measurement (LUM) using a mode-locked laser comb, themode number of the beating comb line must be determined. Peng et al. developed methods based on two
combs with repetition rate difference of kHz to measure the mode number, which can be independent of
the frequency fluctuations of the LUM473, 2. Inaba et al. demonstrated the comb mode determination
using two combs with large difference in repetition rate 3. However, they need long measurement time(1000 s) to average down the uncertainty of the beat frequency difference. In this paper, we report
method based on two-comb technique that can determine the mode number in short average time (1 s)for any different repetition rate.
This method relies on measuring the beat frequencies at two different repetition rates of comb1 while
keeping the repetition rate of comb2 unchanged. Furthermore, a monochromator is used to measure thewavelength of the LUM to offer an approximate frequency to help determining the mode number shift ofcomb1 when its repetition reate is changed. For simplicity, assume that the offset frequencies are zeroand the signs of the beat frequencies are determined to be positive. Thus, the frequency of the LUM canbe expressed as:
fL=nfr11+fb11= kfr21+fb21(1)
fL=(n+m)fr12+fb12= kfr21+fb22(2)
where fb1x and fb2x, x=1 and 2, are the beat frequencies measured at two different repetition rates fr1x of
comb1 and single repetition rate fr21 of comb2; n and k are the mode number of comb1 and comb2,
respectively; m is the mode number shift of comb1 when the repetition rate is changed from fr11 to fr12.
From Eqs. (1) and (2), the mode number n can be derived asnm  f r12  (f b21  f b11)  ( f b 22  f b12 )f r11  f r12(3)

The mode number shift m can be first determined from Eq. (3) by using an approximate n calculated
from the approximate frequency of the LUM similar to that published by Liu et al.2. After m isdetermined, its value is substituted back to Eq. (3) to calculate the exact mode number n. Experimental
results are presented in the conference.

473

J.-L. Peng, T.-A Liu, and R.-H. Shu, “Optical frequency counter based on two mode-locked fiber laser combs,” Appl.
Phys. B, vol. 92, p. 513-518, 2008.
2

T.-A. Liu, R.-H. Shu, and J.-L. Peng, “ Semi-automatic octave-spanning optical frequency counter,” Opt. Express, vol. 16,
p. 10728-10735, 2008.
3

H. Inaba, Y. Nakajima, F.-L. Hong, K. Minoshima, J. Ishikawa, A. Onae, H. Matsumoto, M. Wouters, B. Warrington, and
N. Brown, “Frequency measurement capability of a fiber-based frequency comb at 633 nm,” IEEE Trans. Instru. Meas. vol.
58, p.1234-1240, 2009.

IFCS-EFTF6-PCD6-15

Long-term Miniaturized Stabilization of Ultrafast Laser basedon Rubidium Coherent Population Trapping Atomic
Resonator
Jiutao Wu, Dong Hou, Zhong Wang and Jianye Zhao*
Department of Electronics, Peking University, Beijing, China*Email: zhaojianye@pku.edu.cn
Many locking approaches have been exploited to stabilize the mode-locked laser (MLL), helping to
generate high-stable microwave sources. In conventional locking approaches, the MLLs are usuallyphase-locked to very high-stable external frequency references, including atomic microwave, opticalclocks, and narrow optical-linewidth continuous wave (CW) lasers. These approaches can improve thestability and phase noise of the MLL significantly. However, the large physical size and systemcomplexity of these approaches is a problem in practical application. In this paper, we demonstrate anovel miniaturized MLL stabilization system (length of 5 cm, width of 5 cm and height of 2.2 cm) for
directly frequency-locking the repetition rate of MLL to a 85Rb coherent population trapping (CPT)atomic resonator, generating a stable microwave with a long-term stability of ~3×10-12.
The setup of this MLL stabilization system based on CPT in 85Rb is illustrated in Fig. 1. It contains a
85
Rb CPT resonator with the length of 33 mm, width of 13 mm and height of 18 mm, a passive Er-doped
MLL
withfundamental
repetition rate of 144.5 MHz,and a servo-loop circuit. The
objective of the stabilization
system is to directly frequencylock
the
21stharmonic
repetition rate of the MLL to the85
Rb CPT resonance at a
hyperfine frequency of 3.035
GHz.
By directly transferring thefrequency stability of the atomic
hyperfine frequency to the
MLL, this approach can
improve the frequency stability
85of the MLL significantly, and it Fig. 155: Direct frequency stabilization scheme of MLL with a Rb
can also simplify the system CPT atomic resonator. The stabilization system directly stabilizes therepetition rate of the MLL to the Rb CPT resonance.
complexity and dramaticallyreduce the physical size because of the removal of the PLL servo circuit. Although some PLL
stabilization schemes using high-stable Rb or Cs atomic clocks with big physical size have a better
instability performance, the miniaturized stabilization scheme with a decent long-term stability is justthe advantage of our approach. We believe that the proposed approach have a superior stability to otherstabilization technique with the same small physical size.

IFCS-EFTF6-PCD6-16

Assessing the accuracy of the NPL femtosecond combs for afrequency ratio measurement with 171Yb+
Luke Johnson, Helen Margolis, Steven King, Peter Nisbet-Jones, Rachel Godun, Patrick Gill
National Physical Laboratory, Teddington, Middlesex, UK
Email: luke.johnson@npl.co.uk
Optical clocks are of great interest for the study of fundamental physics. For example, the dimensionlessoptical frequency ratio R = fE3/fE2 between the 171Yb+ octupole and quadrupole optical clock transition
frequencies has a high sensitivity to variations in the fine structure constant α, scaling approximately as
ΔR/R = -6.83 Δα/α 1. Also, without the need to measure relative to the SI second, a ratio measurement
can benefit from the superior stability of the optical standards themselves, significantly reducing
averaging times. Frequency ratio measurements separated by several years will allow a sensitive studyof ∂α/∂t.
To support such measurements at NPL, we present details and results from a recent accuracy evaluationof two independent femtosecond frequency comb systems, based on Ti:Sapphire and Er-fibre modelocked lasers. The optical frequency
ratio between
cavity-stabilised
lasers at 934 nm and 871 nm has
been measured synchronously using
the two comb systems. The two
combs act as transfer oscillatorswith the repetition and carrier
envelope offset frequencies only
loosely locked on both systems2.
Our results show no detectablesystematic offset between the twosystems at the 2 x 10-19 level, which
is limited by the averaging time of
the comparison (see Fig. 1). The
level of agreement is comparable toprevious
comb
comparisons
between Ti:Sapphire systems3. This
performance demonstrates that Fig. 156: Two-comb-comparison stability results between NPL-FC1
171
Yb+
frequency
ratio and NPL-FC3 from a continuous data set of 4600 s. The green
squares and red crosses overlap and show the stability of themeasurements at NPL will befrequency ratio measured using each comb, displaying thelimited by the ion standards rather associated cavity drift of the two lasers. The blue diamonds show
than the femtosecond combs.
the residual stability of the frequency ratio difference between the_____________________________ two systems, which averages down as 1/τ, reaching 2 x 10-19 after_____________________________ 2300 s.
____
1

S. N. Lea, Rep. Prog. Phys. 70 1473 (2007)

3

Long-Sheng Ma et al, Science 303, 1843 (2004)

2

H. R. Telle et al, Appl. Phys. B 74, 1 (2002)

IFCS-EFTF6-PCD6-17

International Timescales with Optical Clocks
H. S. Margolis1, D. Calonico2, P. Delva3, H. Denker4, S. Falke5, R. M. Godun1, D. Piester5,
S. Bize3, J. Gersl6, P. Gill1, T. Lindvall7, C. Lisdat5, L. Lorini2, M. Merimaa7, M. Pizzocaro2,
S. L. Shemar1, U. Sterr5, L. Timmen4, S. Weyers5, P. B. Whibberley1
1

National Physical Laboratory (NPL), Teddington, UK
Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
3
LNE-SYRTE, Observatoire de Paris / UPMC, Paris, France
4
Institut für Erdmessung (IfE), Gottfried Wilhelm Leibniz Universität, Hannover, Germany
5
Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany
6
Cesky Metrologicky Institut (CMI), Brno, Czech Republic
7
Mittatekniikan Keskus (MIKES), Espoo, Finland
2

Email: helen.margolis@npl.co.uk
The most advanced optical atomic clocks have now reached levels of stability and accuracy thatsignificantly surpass the performance of the best caesium primary frequency standards. As a result, thepossibility of a future redefinition of the second in terms of an optical transition frequency is being
actively considered by the international metrology community474.
A new project funded within the European Metrology Research Programme (EMRP) aims to tackle thekey challenges that must be addressed before an optical redefinition of the second can be implemented.
A coordinated programme of European clock comparisons will be carried out at a level limited only by
the accuracies of the clocks themselves, using transportable optical clocks, broad bandwidth satellite
links and optical fibre links. Such a comparison programme is required to validate the performancelevels of the optical clocks, to anchor their frequencies to the present definition of the second with thelowest possible uncertainty, and to establish the leading contenders for a new definition of the second.
To support the comparison programme, a complete evaluation will be made of all relativistic effects
influencing time and frequency comparisons at the 1018 level of accuracy, including the gravitational
redshifts of the clock transition frequencies. Significant effort will be devoted to the design of setups todetermine the static gravity potential at each clock location and the development of a refined geoid
model incorporating gravity observations around each clock site.
The overall objective of the project is to develop a framework and procedures whereby the newgeneration of optical clocks can be integrated into international timescales, providing input to theConsultative Committee for Time and Frequency (CCTF) to prepare for a future redefinition of thesecond. The potential impact that high accuracy optical clocks could have on the field of geodesy will
also be demonstrated, by carrying out a proof-of-principle experiment using optical clocks to measurewith high temporal resolution the gravity potential difference between two well-defined locations
separated by a long baseline (90 km) and a height difference of 1000 m.
The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European
Union.

474

P. Gill, “When should we change the definition of the second?” Phil. Trans. Roy. Soc. A 369, 4109–4130 (2011).

IFCS-EFTF6-PCD6-18

JRP-EXL01: A Joint Research Project of the European Metrology
Research Program to investigate Quantum Engineered States for
Optical Clocks and Atomic Sensors
S. Bize1, J. Lodewyck1, R. Le Targat1,2, G. Wilpers3, U. Sterr4, Chr. Lisdat4, S. Falke4, F. Levi5, D.
Calonico5, A. Bertoldi6, M. Chwalla7, C. Klempt8 and the JRP-EXL01 collaboration
1

LNE-SYRTE, Observatoire de Paris, LNE, CNRS, UPMC, Paris, France
2
Laboratoire National de Métrologie et d’Essais (LNE), Paris, France
3
National Physical Laboratory (NPL), Teddington, United Kingdom
4
Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany
5
Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
6
LP2N, Institut d’Optique Graduate School, Bordeaux, France
7
Institute for Quantum Optics and Quantum Information (IQOQI), Innsbruck, Austria
8
Leibniz Universität Hannover, Hannover, Germany
Email: sebastien.bize@obspm.fr
The best optical clocks today have accuracies around 1 part in 1017. Accuracies of 10-18 will be possible
in the near future. However, investigating the physical phenomena, understanding the associated shiftsof the clock frequency and using clocks at the 10-18 level is currently hindered by the prohibitively long
averaging time needed to measure at this level. In current state-of-the-art systems, the stability is limitedby two main causes, depending on the type of system. One limitation arises from the limited number ofparticles used for the clock, via the standard quantum projection noise, which is inversely proportional
to the square root of the number of particles. The second limitation (called Dick effect) is due to thelarge amount of dead time of the sequence used to probe the clock transition combined with the probe
laser frequency noise. This dead time is associated with the need to gather, to cool and to prepare atoms
before the probe period and to detect the atomic state after probe period.
The use of quantum-entangled states can provide a mean to overcome these limitations. In this poster,we will give an overview of the recently started JRP-EXL01 project of the European Metrology
Research Program (EMRP) aimed at exploring these possibilities. Limitations faced by optical clocks
are reminiscent of limitations in other atom-based sensors, such as accelerometers, gravimeters,
gyrometers or magnetometers. The research undertaken within JRP-EXL01 will benefit all thesesensors. JRP-EXL01 is designed to account for the need of these sensors and more generally, tomaximize exchanges and cross-fertilization between optical clocks and several other fields: atominterferometry, quantum gases, quantum information processing.
The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European
Union.

IFCS-EFTF6-PCD6-19

A Space-Based Optical Kennedy-Thorndike Experiment
Testing Special Relativity
Thilo Schuldt1,2, Sven Herrmann2, Deborah Aguilera1,2, Klaus Döringshoff3, Ruven Spannagel1,2, Claus
Lämmerzahl2, Achim Peters3, Bernd Biering1, Hansjörg Dittus1, Claus Braxmaier1,2
1

2

DLR Institute for Space Systems, Bremen, Germany
Center for Applied Space Technology and Microgravity (ZARM), University Bremen, Germany
3Institute for Physics, Humboldt-University Berlin, Germany
Email: claus.braxmaier@dlr.de

We propose a small satellite mission that aims for testing the foundations of special relativity by
performing a Kennedy-Thorndike (KT) experiment. A potential boost anisotropy of the velocity of lightis measured by comparing a length reference (i.e. a highly stable optical resonator) with a molecularfrequency reference. By employing clocks with 1*10-16 frequency stabilities at orbit time (~90 min) andby integration over 5000 orbits (corresponding to a 2 year mission lifetime with 50% duty cycle) a 1000fold improvement in measuring the Kennedy-Thorndike coefficient is targeted, compared to the current
best terrestrial test.
The experiment uses state-of-the-art laser technology. For realizing a small satellite compatible payload,
the use of diode-laser technology is favorable and currently already under investigation with respect toother space experiments. A laser wavelength of 1016nm is foreseen as its second harmonics accesses
narrow linewidth transitions in molecular iodine. For the KT experiment, one laser is stabilized to a highfinesse cavity and a second laser is frequency doubled to a wavelength of 508nm and stabilized to a
hyperfine transition in molecular iodine. Both lasers are directly compared in a beat measurement andanalyzed with respect to a possible boost dependency of the speed of light.
In the last years, we realized an iodine-based frequency reference at a wavelength of 532nm on elegant
breadboard (EBB) level where a frequency stability of 3*10 -15 at 1000s integration time wasdemonstrated in a beat measurement with a laboratory-type cavity setup. In a current activity the iodine
frequency reference is further developed with respect to compactness and thermal and mechanicalstability. A compact iodine setup on engineering model (EM) level is currently developed using a fusedsilica baseplate with dimensions of 18cm x 35cm x 4cm, where the optical components are directly
glued to, and a 10cm x 10cm iodine cell in nine-path configuration. The EM setup will be subjected toenvironmental tests such as vibration and thermal cycling. Using a corresponding laser system, the EM
design can easily be adjusted to a wavelength near 508nm, where molecular iodine offers hyperfine
transitions with more narrow linewidths than at 532nm, leading to a further increase in frequency
stability by up to one order of magnitude.
In a parallel activity, the development of a space compatible optical resonator setup with a resonatorfinesse of 105 and a controlled temperature stabilization at the ~1µK level is planned.
Techniques for laser frequency stabilization are key technologies not only for the proposed KT
experiment mission but also for a variety of other future space missions such as LISA/NGO, GRACEFO, and missions using aperture-synthesis such as Darwin/TPF.

IFCS-EFTF6-PCD6-20

AOM-RN: an acousto-optic modulator extending the tools
employed in laser spectroscopy as optical phase modulators
V.N. Baryshev
FGUP “VNIIFTRI”, Mendeleevo, Moscow Region, Russian Federation
Email: baryshev@vniiftri.ru
This report completes the series of studies [1 and references therein] devoted to the experimental
demonstration and justification for applying AOM-RN as a phase modulator in frequency modulation(FM) heterodyne spectroscopy of optical resonances. Fabricated at VNIIFTRI AOM-RN design issignificantly simplified and its dimensions are minimized due to a decrease (by almost an order ofmagnitude in comparisons with existing AOMs) in the acousto-optic interaction length and the absenceof impedance matching circuit (fig. 1).
The AOM-RN has the following advantages over electro-optic phase modulators (EOM): compactness,
low energy consumption, wide range of modulation frequencies, and the absence of necessity to control
the input and output polarizations.
The report is mainly devoted to the experimental confirmation of the last statement. Since the existing
EOMs do not produce a pure FM spectrum due to the residual amplitude modulation (RAM) arisingfrom étalon effects and birefringence properties of the electro-optic crystals [2], one has to control thepolarization of the input and output beams and to angling the laser beam incidence onto the EOM inorder to remove the residual amplitude noise. An investigation of the RAM, étalon and birefringenceeffects in particular case of AOM-RN based on the TeO2 monocrystal with shortened to 2 mm acoustooptic interaction length will be presented.
AOM-RN

Monocrystals

Fig. 1. The photographs of commercial AOM of “ISOMET” model
1205С-2 and AOM-RN without impedance matching circuit.
___________________________________
1

V. Baryshev, V. Epikhin, S. Sliusarev, “Use of AOM-RN as a Phase Modulator in FM Sideband Heterodyne Technique in
the Atomic Frequency Standards”, In Proc. of 2011 Joint Conference of the IEEE IFCS & EFTF, San-Fransisco, California,
USA, pp. 709-712, 2011.
2
E. Whittaker, M. Gehrtz, and G. Bjorklund, “Residual amplitude modulation in laser electro-optic phase modulation”, J.
Opt. Soc. Am. B, vol. 2, No. 8, 1320-1326, 1985.

IFCS-EFTF6-PCD6-21

High performance laser stabilization
using a Ramsey-Borde spectrometer
A. D. Ludlow1, R. W. Fox1, J. A. Sherman1, J. B. Olson1,2,
E. de Carlos-Lopez1,3, W. Douglas1, C. W. Oates1
1Time & Frequency Division, National Institute of Standards and Technology,
Boulder, Colorado USA
2
Department of Physics, University of Colorado, Boulder, Colorado USA
3
Centro Nacional de Metrologia, Queretaro, Mexico
Email: ludlow@boulder.nist.gov

Optical atomic clocks, coherent optical transfer and communication, and low-phase noise optical signal
generation and division require highly-phase-stable optical sources. Commonly, these sources arederived from lasers that are phase or frequency stabilized to high finesse optical cavities. Suchstabilized lasers have achieved fractional frequency instability approaching the 1x10 -16 level. Thesestate-of-the-art stabilized-lasers are sensitive to a fundamental limitation caused by Brownian thermalmechanical noise of the optical cavity components, which complicates the continued improvement in theperformance of these systems.
Here, we explore an alternative approach to highperformance laser stabilization by implementing ahigh resolution atomic-beam spectrometer.
The
spectrometer
employs
4-zoneRamsey-Borde
spectroscopy of the 1S0-3P1 transition in a thermal
beam of calcium.
We observe Doppler-freelineshapes with < 5 kHz resolution, comparable to themode linewidth of high finesse optical cavities.
Furthermore, the system is designed to achieve very
high signal to noise ratio (S/N). By collecting
fluorescence decay from the 3P1 state at 657 nm after
the Ramsey-Borde interrogation, we have observed a
S/N approaching 1000 at 1 s. Under such conditions,the atom-stabilized laser exhibits an instability as
good as 5x10-15 at 1 second. Such a system could
serve as a simple, one-laser high stability frequency Fig. 157: Ramsey-Borde fringes from the calcium
reference for a variety of precision timing spectrometer used for laser stabilization. The fringe
applications. Furthermore, we have constructed a laser resolution of 4.5 kHz gives clear visibility of thesystem at 431 nm as part of an improved detection recoil doublet.
scheme using the 3P1-3P0 cycling transition, capable ofenhancing the S/N by more than an order of magnitude. Together with additional efforts to enhancedetection efficiency and reduce the observed Ramsey linewidth to less than 2 kHz, this system has thepotential for stability competitive with the best cavity-stabilized lasers.

Space missions and clocks II
CLUB HThursday, July 25 2013, 08:30 am - 10:00 am
Chair:

Kurt Gibble
Penn StateIFCS-EFTF3-K1-1

Status of the flight model of the cold atoms spaceclock PHARAO
1

1

1

1

1

Igor MORIC , Philippe LAURENT , Michel ABGRALL , Pierre LEMONDE , Giorgio SANTARELLI , André
1
1
1
1
2
3
CLAIRON , Sébastien BIZE , Daniele ROVERA , Jocelyne GUÉNA , Christophe SALOMON , Frédéric PICARD ,
3
3
3
3
3
Olivier GROSJEAN , Christophe DELAROCHE , Jean-François VÉGA , Benoît LÉGER , Muriel SACCOCCIO ,
3
3
3
3
3
3
Isabelle ZENONE , Benoît FAURE , Christian SIRMAIN , Didier MASSONNET , Sylvie LÉON , Serge BÉRAUD ,
3
3
3
3
3
Fabrice BUFFE , Philippe LARIVIÈRE , Claude ESCANDES , Nadine LADIETTE , Bernard VIVIAN , Didier
3
3
3
4
4
BLONDE , Michel CHAUBET , Clément LUITOT , Philippe CHATARD ,Charles Marie DE GRAEVE , Christian
5
5
5
6
6
7
MACÉ , Stéphane THOMIN , Jean Pierre LELAY , Thierry POTIER , Yoann COSSART , Thierry NAULEAU ,8
Arnaud GRANGET .
1
2

LNE-SYRTE, 61 av. de l’Observatoire, 75014 PARIS, France.

Laboratoire Kastler-Brossel, CNRS, 24 rue Lhomond, 75231 PARIS, France.
3

CNES, 18 avenue Edouard Belin, 31401 TOULOUSE Cedex, France
4

5

Sodern, 20 Avenue Descartes,B.P. 23, 94451 LIMEIL-BREVANNES Cedex, France.
6

7

Sogeti, 24, rue du Gouverneur Général Eboué
92136 Issy-les-Moulineaux Cedex, France

THALES, 2 avenue Gay-Lussac, 78851 ELANCOURT Cedex, France

CS SI, ZAC de la Plaine – Rue Brindejonc des Moulinais, – BP 5872, 31506 TOULOUSE Cedex 5, France
8

EREMS, Chemin de la Madeleine, ZI, 31130 FLOURENS, France.

PHARAO (Projet d'Horloge Atomique par Refroidissement d'Atomes en Orbite), which is
being developed by the French space agency CNES, is the first Primary Frequency
Standard (PFS) specially designed for operation in space. PHARAO is a main
instrument of the ACES (Atomic Clock Ensemble in Space) mission. ACES is being
developed by ESA and the payload will be installed on-board the International Space
Station. The mission is based on comparisons with ground based clocks to performfundamental physics experiments: gravitational redshift measurements, analysis of
the stability of the fundamental constants and anisotropy of light. Planned
duration of the mission is 18 months with a possible extension to 36 months. The
frequency accuracy requirement for PHARAO is less than 3 x 10-16 and the expected
frequency stability is 10-1312.
An engineering model of PHARAO has been constructed and fully tested to validate
the clock architecture. Two sub-systems for the flight model(FM) have beendelivered: the cesium tube where the atoms are manipulated and the microwave source
which generates the 9.2 GHz signals. The other sub-systems, the laser source andthe computer, will be delivered this year. In this talk we will present the
preliminary tests performed on the FM cesium tube and on the FM microwave source.
To operate the cesium tube with cold atoms, it has been connected to theengineering model of the laser source. The goal is to measure the magnetic andthermal properties of the cesium tube in the orbit-like magnetic and thermal
environments and deduce the blackbody radiation and the second order Zeeman
correction uncertainties. Other effects will be evaluated when the whole FM clock
is assembled.

IFCS-EFTF3-K1-2

Lifetime of Space Passive Hydrogen Maser
Qinghua Wang, Pierre Mosset, Fabien Droz, Pascal Rochat
Orolia Switzerland Inc, Neuchatel, Switzerland
Email: qinghua@spectratime.com
Accurate and ultra-stable space qualified atomic clocks represent critical equipment for the precision
global navigation satellite systems. The Passive Hydrogen Maser (PHM), with its excellent frequency
stability performance, is the master clock for European Galileo navigation payload, and is the first oneof its type ever to fly. The PHM technology has flight heritage of several years through Galileo satellites(GIOVE-B and four IOV satellites) since Apr. 2008. More than thirty PHM flight physics packages havebeen manufactured and characterized by SpectraTime (under the industrial consortium led by Selex ES
S.p.A).
Besides radiation effects on electronic components, lifetime in PHM depends on the lifetime of thephysics package. In the frame of the “Lifetime Qualification of the PHM”, two Qualification Model(QM) units had been subjected to test under vacuum since 2008. After the first 1.5-year test period asreported in previously published papers475,476, one QM has been extended for another 2-year lifetime
test. This paper provides test results of the overall period, and gives further comparison and analysis of
key parameters of the physics package for 3.5 years of operation or 4 years including stay-alive period.
The extended test provides additional statistical element, and obtains valuable results and better
confidence to PHM lifetime evaluation, showing the compliance with Galileo requirements.

475 F. Droz, P. Mosset, Q. Wang, P. Rochat, M. Belloni, M. Gioia, A. Resti, and P. Waller, “Space Passive Hydrogen Maser– Performances and lifetime data”, Proceedings of the Joint 2009 European Frequency and Time Forum & 2009 IEEE
Frequency Control Symposium, 20-24 April, 2009, Besançon (France), pp 393-398.
476 M. Belloni, M. Gioia, S. Beretta, F. Droz, P. Mosset, Q. Wang, P. Rochat, A. Resti, P. Waller, and A. Ostillio, “Space
Passive Hydrogen Maser - Performances, Lifetime Data and Giove-B Related Telemetries”, 41st Precise Time and TimeInterval (PTTI) Systems and Applications Meeting, 16-19 Nov. 2009, Santa Ana Pueblo (USA).

IFCS-EFTF3-K1-3

STE-QUEST: Atomic sensors in space forfundamental physics, time and frequency metrology
and other applications
P. Tuckey1 for the STE-QUEST collaboration477
1

LNE-SYRTE, Observatoire de Paris, CNRS, LNE, UPMC, Paris, France
Email: philip.tuckey@obspm.fr

STE-QUEST – Space-Time Explorer and Quantum Equivalence Principle Space Test – is a candidate
mission for the M3 flight opportunity of the European Space Agency’s Cosmic Vision 2012-2025
programme (see http://sci.esa.int/ste-quest). STE-QUEST is currently undergoing a phase A study, inview of a possible launch in 2022-2024. This mission is designed to test different aspects of the Einstein
Equivalence Principle: the gravitational time dilation effect and the universality of free fall in the case ofmatter waves, and to carry out studies on a variety of other subjects: atomic time scales, high-precision
long-distance ground clock comparisons, long-distance relative geopotential measurements, microwave
and optical ranging, cold-atom physics, etc. To achieve these objectives, the payload includes an atomic
frequency standard, microwave and optical time and frequency links and an atom interferometer. This
paper proposed here will discuss the mission objectives and present the results obtained thus far in theongoing study.
The STE-QUEST clock is a modified version of the PHARAO clock, presently being developed in theframe of the ACES mission. In order to maximize the benefit of the PHARAO heritage, it has been
decided to also use a Caesium clock for STE-QUEST, meaning that the physics and laser packages will
be very similar to those of PHARAO. The local oscillator will however be significantly improved, using
a femtosecond comb to down-convert the optical frequency from a laser stabilized on a high finesse
cavity. The on-board clock aims to achieve an instability of 8x10-14 t-1/2 at long times, where t is theintegration time, and an inaccuracy of the order of 1-2x10-16. High performance links, both in the
microwave and optical domains, will compare the space clock with clocks on the ground. A highly
elliptical orbit has been chosen in order to provide access to a strong gravitational time dilation effect at
the apogee, as well as a significant modulation of this effect at the perigee, with the aim of measuring
the effect due the field of the Earth to an inaccuracy of 2x10-7. A consequence of this strategy is a quite
harsh radiation environment for the payload instruments. STE-QUEST will also perform common-view
comparisons of terrestrial clocks located on different continents and it will measure the periodic effect of
the gravitational frequency shifts induced by the Sun and the Moon.
Concurrently to the clock measurements, a two-isotope matter-wave interferometer will measure thedifferential acceleration between two Bose-Einstein condensates composed respectively of 85Rb and87
Rb atoms. The atom interferometry measurement will be particularly important around perigee, where
the signal-to-noise ratio of a possible violation of the Weak Equivalence Principle can be maximized.
This instrument will test the universality of the free propagation of matter waves to an uncertainty in the
Eötvös parameter of the order of 2x10-15.

477

The STE-QUEST collaboration is rather large compared with the format of the abstract; a full author list will be provided
with the paper.

IFCS-EFTF3-K1-4

ACES data simulation and data analysis: an update
P. Wolf1, P. Delva1, C. Le Poncin Lafitte1, F. Meynadier1
1

LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France
Email: peter.wolf@obspm.fr

The Atomic Clocks Ensemble in Space (ACES/PHARAO mission), which will be installed on board theInternational Space Station (ISS), uses a dedicated two-way MicroWave Link (MWL) in order tocompare the timescale generated on board with those provided by many ground stations disseminated on
the Earth. The phase stability of this long range link is specified to reach 0.3 ps after 300 s integration
time, with long term stability better than 7 ps over 10 days. This link will play a key role in the successof the ACES/PHARAO experiment.
The SYRTE laboratory is heavily involved in the design and development of the data processing
software : from theoretical modeling and numerical simulations at the required precision to thedevelopment of the SYRTE data analysis software. Our team is working on a wide range of problems
that need to be solved in order to achieve the required stability in (almost) real time.
We present some key aspects of the measurement, as well as current status of the software's
development, including the results of tests with simulated data. We put particular emphasis on thescientific products that will be provided to the users and discuss how those products can be used for the
purposes of time/frequency metrology.

IFCS-EFTF3-K1-5

Next Generation JPL Ultra-Stable Trapped Ion Atomic Clocks
Eric Burt, Blake Tucker, Kameron Larsen, Robert Hamell, John Prestage, and Robert Tjoelker
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
Email: eric.a.burt@jpl.nasa.gov
Over the past decade, trapped ion atomic clock development at the Jet Propulsion Laboratory (JPL) has
proceeded in two parallel directions: 1) new atomic clock technology for space flight applications that
require strict adherence to size, weight, and power requirements, and 2) ultra-stable atomic clocks,
usually for terrestrial applications focusing on ultimate performance. In this paper we will present first
results from two new ultra-stable trapped ion clocks in the second category currently underdevelopment.
The new identical clocks, designated L10 and L11, build on the successful demonstration of
exceptionally low drift at the 3x10-17/day level478 by their predecessor, LITS-9, with changes in design
intended to improve ultimate long-term performance. The first will be delivered to the Naval ResearchLab, while the second, and eventually a third and fourth designated L12 and L13, will be retained as inhouse standards at JPL.
The excellent long-term stability of LITS-9, and the anticipatedequivalent or better performance of L10 and L11, has bothengineering and scientific applications. It will be invaluable forcharacterizing the performance of flight clocks both at JPL and
NRL, as well as that of clocks being delivered to, and operated
NASA’s Deep Space Network. In addition, L11 will also be
as a reference for an ACES ground station479 at JPL when the
ACES laser-cooled atomic clock becomes operational on theInternational Space Station in the 2016 time frame.

at
in
used

As with LITS-9, L10 and L11 use a quadrupole trap for loading ions and a separate 12-pole480 trap forsensitive microwave clock interrogation that greatly reduces one of the largest systematic effects in thistype of clock, the second order Doppler (SOD) shift. A key additional enhancement to LITS-9 was theuse of magnetic compensation to reduce the SOD by a further order of magnitude 1. The newer clocks
use an improved version of magnetic compensation fully integrated into the design. Other
enhancements include a sealed vacuum system bakeable to 450 C for improved stability of backgroundgases, improved magnetic field uniformity, enhanced microwave coupling, improved optical efficiency,
and a dedicated FPGA-based controller for better reliability.
The new standards are being assembled and tested in parallel. At present, we have observed a narrow
clock transition in the L11 multi-pole trap and have observed trapped ions in the quadrupole trap of L10.
In this paper we will describe the improvements to L10 and L11 that focus on better long-term
performance and show the first results obtained from operating the new standards.

478

E.A. Burt, W.A. Diener, and R. L. Tjoelker, IEEE Trans. UFFC 55, 2586 (2008)

479

E. Daganzo, et al., Proceedings of the 2009 joint IFCS-EFTF, 1146 (2009)

480

J.D. Prestage, R.L. Tjoelker, and L. Maleki, Proceedings of the 1999 joint IFCS-EFTF, 121 (1999)

Optical fiber T+F Transfer III
CLUB E
Thursday, July 25 2013, 08:30 am - 10:00 am
Chair:

Anne Amy-Klein
LPL

IFCS-EFTF5-K2-1

A 30-km-long optical fiber link for frequency comparison
between distant strontium optical lattice clocks
Tomoya Akatsuka1,2, Hitomi Ono1,3, Keitaro Hayashida1,3, Kuniya Araki1,3,
Masao Takamoto1,2, Tetsushi Takano1,3, and Hidetoshi Katori1,2,3
1Innovative Space-Time Project, ERATO, JST,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
2
Quantum Metrology Laboratory, Advanced Science Institute, RIKEN,
2-1 Hirosawa, Wako, Saitama 351-0198, Japan3
Department of Applied Physics, Graduate School of Engineering, The University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
Email: akatsuka@riken.jp
Recently, frequency comparison between two Sr optical lattice clocks demonstrated the quantum
projection noise (QPN) limited stability of a few times 10-16-1/2 by synchronously operating the twoclocks481. Further improvement by more than one order of magnitude is promising in the near future.
Such a clock stability enables to probe the relativistically-curved space-time in real time. Because of its
sensitivity to the gravitational potential, frequency comparison between two clocks operating at distantsites allows monitoring temporal fluctuation of the gravitational potential difference, which can lead to
new applications in relativistic geodesy482. Coherent optical frequency transfer via optical fiber networks
serves as an essential technique for frequency link between distant sites, though the link stability
deteriorates as the fiber length increases because of the uncompensated fiber noise due to time delay483.
In order to demonstrate frequency comparison between distant clocks at the stability of 10-17-1/2, wehave developed a 30-km-long optical fiber link between Riken and the University of Tokyo located 15
km apart from each other.
Since we focus on frequency comparison between two Sr optical lattice clocks operating with 698 nm
clock lasers, we implemented a novel scheme utilizing a 1397 nm transfer light which directly links tothe clock frequency by the second harmonic generation (SHG). This scheme avoids the need ofoperating optical frequency combs where associated phase noises have to be analyzed carefully.
Although conventional single-mode fibers have water-peak attenuation due to OH radical around 1383
nm, it is not a serious problem for the 30-km-long fiber, which causes additional transmission loss of 7dB compared with 1550 nm light. In the future, OH-free fiber will be more popular for coarse
wavelength division multiplexing (CWDM) application, which allows the frequency transfer in longer
distance at this wavelength. Our scheme provides a simple platform for networking Sr optical latticeclock which has already become the most widespread optical clock.
We demonstrate an optical beat measurement between two clock lasers operating at the distant sites via
the fiber link. The link stability was evaluated to be a few times of 10 -17 for an averaging time of 1 s,
which encourages the frequency comparison between distant clocks.
481

M. Takamoto, T. Takano, and Hidetoshi Katori, “Frequency comparison of optical lattice clocks beyond the Dick limit”,
Nat. Photon., vol. 5, p. 288-292, 2011.

482
483

H. Katori, “Optical lattice clocks and quantum metrology”, Nat. Photon., vol. 5, p. 203-210, 2011.

N. R. Newbury, P. A. Williams, and W. C. Swann, “Coherent transfer of an optical carrier over 251 km”, Opt. Lett., vol.
32, p. 3056-3058, 2007.

IFCS-EFTF5-K2-2

Optical Frequency Transfer over a single-span
1840 km Fiber Link
1

S. Droste, F. Ozimek,2,3 S. M. F. Raupach,2 H. Schnatz,2 G. Grosche,2T. W. Hänsch,1 Th. Udem,1 and R. Holzwarth1
1

Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
3
University of Warsaw, Faculty of Physics, ul. Hoza 69, 00-681 Warszawa, Poland

2

Email: stefan.droste@mpq.mpg.de
The development of optical frequency standards484 raises a demand for transferring highly stable opticalsignals over continental distances. Such transfer would enable new experiments485, and will be mandatory fora future redefinition of the SI-second based on optical frequency standards. We investigate optical frequency
transfer via a 1840 km fiber link connecting Physikalisch-Technische Bundesanstalt (PTB) and Max-PlanckInstitute of Quantum Optics (MPQ). The link consists of a pair of dark fibers486, and is set up in a loop
configuration with sender and receiver located at MPQ. It thus involves a single-span 1840 km stabilization.
We use 20 Erbium-doped fiber amplifiers, and a fiber Brillouin amplifier at each institute, compensating for
420 dB loss.
Fig. 1 shows the instability of the transferredfrequency after 1840 km of fiber for the stabilized
fiber link, expressed as the Allan deviation (ADEV)
and the modified ADEV. The servo bandwidth forthe suppression of fiber-induced noise is limited toabout 27 Hz due to the propagation delay of the lightof around 18 ms. However, the low intrinsic noise of
the fiber link together with active noise cancellation
allow us to reach instabilities (modified ADEV) of
2.7 x 10-15 at 1 s, and about 4 x 10-19 after 100 s ofintegration time. The noise of the link peaks around
15 Hz and is lower at smaller frequencies whichleads to a τ-2 dependency in the modified ADEV as
shown in Fig. 1.

Fig. 158: Fractional frequency instability of the
To assess potential systematic frequency shifts, we 1840 km stabilized link (squares) expressed as
analyzed the mean deviation of the transferred the ADEV. To distinguish between white phase,frequency from the input frequency, and found flicker phase and other noise types the modified
agreement within the statistical uncertainty of 2.6 x ADEV (solid circles) is also shown.
10-19. The results illustrate that for a remotecomparison of state-of-the-art optical clocks, the short-term instability contribution of the stabilized ~2000
km link is negligible within one minute of integration time.
This work was supported by the European Metrological Research Programme EMRP under SIB-02 NEAT-FT. The EMRP is
jointly funded by the EMRP participating countries within EURAMET and the European Union.

484

N. Huntemann, et al., Phys. Rev. Lett. 108, 090801 (2012).

485

C. W. Chou, et al., Science 329, 1630 (2010).

486

K. Predehl, et al., Science 336, 441 (2012).

IFCS-EFTF5-K2-3

Distributed Raman Amplification for long-haul opticalfrequency dissemination
C. Clivati1,2, G. Bolognini3, D. Calonico1, G. A. Costanzo1,2,
Faralli4, F. Levi1, A. Mura1, N. Poli5

S.

1

Istituto Nazionale di Ricerca Metrologica, Torino, Italy
2
Politecnico di Torino, Torino, Italy3
Consiglio Nazionale delle Ricerche, IMM Institute, Bologna, Italy;
4
Scuola Superiore S. Anna, Istituto TeCIP, Pisa, Italy;
5
Dip. di Fisica e Astronomia and LENS, Università di Firenze, INFN, sezione di Firenze, Italy
Email: c.clivati@inrim.it
Phase-compensated optical links are the most performing technique to disseminate optical frequencies
on a continental scale1,2. Most National Metrology Institutes are thus cooperating to realize a panEuropean fiber network, that will enable optical clocks comparisons at unprecedented levels of accuracy
and stability. Dedicated amplification systems are thus needed, that have to be fully bidirectional toallow the compensation of the fiber phase noise. Bidirectional Erbium Doped Fiber Amplifiers are used,
but their gain is limited by the back-reflections along the path, that may lead the amplifier to oscillate.
Distributed Brillouin Amplifiers are much promisingfrom this point of view3. We demonstrate that
10
Distributed Raman Amplification (DRA) is areliable technique as well, not degrading the transferof the optical carrier at the 10-19 level of stability
10(see Fig. 1), and allowing to bridge hauls of 60 dB
losses (i.e. more than 250 km) without intermediate
amplification stations4.
10
Fractional frequency instability 

-16

-17

-18

We implemented DRAs on a 200 km optical link in
the laboratory, evaluating gain, signal-to-noise ratio
10
1
10
100
1000
and phase noise added to the carrier. Nonlinear
Averaging time /seffects have been observed with a not optimized
amplifier placement, resulting in degraded amplifier Fig. 159: Fractional frequency stability of theperformance. At the conference, we will present the
200 km optical link using DRA.
set-up, the results and the perspectives forapplication on the Italian Optical Fiber Link for Frequency and Time (LIFT).
-19

1. K. Predehl, G. Grosche, S. M. F. Raupach, S. Droste, O. Terra, J. Alnis, Th. Legero,T. W. Hansch, Th. Udem, R.
Holzwarth, H. Schnatz, “A 920-Kilometer Optical Fiber Link for Frequency Metrology at the 19th decimal place,” Science
336, 441-444 (2012).
2. O. Lopez, A. Haboucha, F. Kefelian, H. Jiang, B. Chanteau, V. Roncin, C. Chardonnet, A. Amy-Klein, G.
Santarelli,“Cascaded multiplexed optical link on a telecommunication network for frequency dissemination,” Opt. Expr. 18,16849-16857 (2010).
3 O. Terra, G. Grosche, and H. Schnatz, “Brillouin amplification in phase coherent transfer of optical frequencies over 480
km fiber,” Opt. Expr. 18, 16102-16110 (2010).
4. C. Clivati, G. Bolognini, D. Calonico, S. Faralli, F. Levi, A. Mura, N. Poli, arXiv:1211.3910.

IFCS-EFTF5-K2-4

Two Color One-Way Frequency Transfer in an Urban Optical Fiber
NetworkSven-Christian Ebenhag* and Per Olof Hedekvist*
SP Technical Research Institute of Sweden, Boras, Sweden*also with Department of Microelectronics, Photonics Lab
Chalmers University of Technology
Göteborg, Sweden
Email: sven-christian.ebenhag@sp.se

SP Technical Research Institute of Sweden has previously presented results with a two color one- way
method. This method is an alternative method to two-way time and frequency transfer that is useful if
there are unknown asymmetries in the connection. The method is possible to use in existing
infrastructure and is able to coexist with data channels for example in WDM systems, which make itpossible to broadcast to multiple users and enables the user to be anonymous to the time or frequency
transfer.
This paper will present the results from implementing the technique in an urban commercial optical fiber
data communication WDM network between two clock labs in Sweden connecting two cesium clocks toeach other for frequency transfer. The evaluation is performed with two wavelengths 8nm apart on 6 kmof installed fiber in an urban city network. The transmitter and the receiver are installed in anelectromagnetically shielded room several meters below ground, and the fiber runs to a building at a
distance of 3 km, and then back again. The comparison will be within the laboratory, eliminating any
errors from a reference system. Results and conclusion from this evaluation reveals the propagation
delay variations in the propagation distance and will display the need of compensation for thesevariations.

IFCS-EFTF5-K2-5

Optical Frequency Transfer on Branching Fibre Networks
Sascha W. Schediwy1, David Gozzard1, Guido Aben2, Kenneth G. H. Baldwin3,Brian J. Orr4,
R. Bruce Warrington5, Andre Luiten1,6
1School of Physics, University of Western Australia, Perth, Australia
Australia’s Academic and Research Network (AARNet), Perth, Australia
3
Research School of Physics and Engineering, The Australian National University, Canberra, Australia
4
Department of Physics and Astronomy, Macquarie University, Sydney, Australia
5
National Measurement Institute, Sydney, Australia
6
School of Chemistry & Physics, The University of Adelaide, Adelaide, Australia
2

Email: sascha.schediwy@uwa.edu.au
Ultra-precise time and frequency transfer via optical-fibre has developed rapidly over the last decade.
Most progress has focused on the stabilisation of links between two fixed nodes. Recently a techniquethat provides stabilised signals at intermediate nodes along a fibre link was proposed for opticalfrequency transfer487 and demonstrated for microwave frequency transfer488. Nonetheless, this technique
is mainly aimed at fibre networks with a linear topology.
We present a technique that can be used to distribute optical-frequency signals to multiple nodes on abranching optical-fibre network. Optical-fibre fluctuations are corrected at the output of the link rather
than at the input. As the transmitted optical signal remains unaltered until it reaches the remote location
it can be transmitted to multiple nodes simultaneously. Other techniques can only recreate such a
branching network by ‘daisy-chaining’ stabilised
1 km
5 km
Local
Remote A
links, thereby requiring that every stabilised link inν0 = 193 THz
νA = 40 MHz
the chain must be working correctly at all times.
We investigated this technique experimentally using
1 km
Remote B
the simplest configuration that demonstrates all theνB = 70 MHz
essential features of a branching network (seeFigure 1). For Remote A, the out-of-loop fractionalfrequency stability of the free-running transfer was
Remote Ωmeasured to be (3.1±0.4)×10−14 at 1 s of integration.
νΩWith the Remote A stabilisation control engaged, thetransfer stability was (1.1±0.1)×10−17 at 1 s while Fig. 160: Experimental implementation of theRemote B was disconnected from the network, and multibranch optical-fibre stabilisation technique(1.2±0.1)×10−17 at 1 s when Remote B was included implemented on a two node network (solid green
in the network. The equivalent measurement for lines); Remote A and Remote B. The dashed lightgreen lines show an example of further branching.
Remote B produced corresponding results. We
concluded that the inclusion of the extra node has negligible impact on the transfer stability, and thus thetechnique lends itself to applications such as the Square Kilometre Array, research campuses, or
metropolitan areas where branching fibre networks are the most efficient configuration to transfer
signals from a master site to many subsidiary remote nodes.
487

G. Grosche, "Verfahren zum Bereitstellen einer Referenz-Frequenz," DPMA Patent application DE 10 2008 062,139(2010).
488

C. Gao, et al., "Fiber-based multiple-access ultrastable frequency dissemination," Opt. Lett. 37, 4690-4692 (2012).

IFCS-EFTF5-K2-6

Fiber-based multiple-access ultrastable optical and radio
frequency dissemination
Y. Bai1,3, B. Wang1,2, C. Gao1,3, W. L. Chen4, J. Miao1,3, X. Zhu1,3, and L. J. Wang1,2,3,4
1

2

Joint Institute for Measurement Science, Tsinghua University, Beijing 100084, China
The State Key Laboratory of Precision Measurement Technology and Instrument, Department ofPrecision Instruments, Tsinghua University, Beijing 100084, China
3
Department of Physics, Tsinghua University, Beijing 100084, China
4
National Institute of Metrology, Beijing 100013, China

Email: bo.wang@tsinghua.edu.cn
The multiple-access frequency dissemination is one of key technologies for a time and frequency
network. We propose fiber-based multiple-access ultrastable frequency dissemination schemes for radio
frequency (RF) and optical frequency, separately.
For the RF dissemination, we build up a time andfrequency dissemination system via the 80 km
urban telecommunication fiber link between
Tsinghua University (THU) and the National
Institute of Metrology (NIM) of China1. Using the
proposed multiple-access RF dissemination scheme,
the 9.1GHz disseminated RF signal with relative
frequency stability of 7×10-14/s and 5×10-18/day canbe reproduced at arbitrary nodes along the entire
fiber pathway (as shown in Fig.1). For the opticalfrequency dissemination, G. Grosche proposed atechnique for multiple access optical frequency Fig. 161: Measured relative frequency stability ofdissemination in 20103. However, in the scheme, a the reproduced 9.1GHz signal at an arbitrary
accessing node of the fiber link. (a) signal directly
highly stable laser source whose wavelength isdetected, (b) signal obtained using the multiplesame with the disseminated optical signal is needed access RF dissemination method.
at an arbitrary accessing node to reproduce thehighly-stable disseminated signal. It makes the system costly and technically complex. In this paper, we
propose a more convenient and efficient scheme to solve this problem and the results will be presented
in detail during the conference. Optical frequency transfer can provide better stability while the RF
dissemination is relatively simple for practical applications. Using this method, we can regenerate thehighly synchronized RF signal or the optical signal along the entire fiber link, which is crucial for a timeand frequency network.
References:
1. B. Wang, C. Gao, W. L. Chen, J. Miao, X. Zhu, Y. Bai, J. W. Zhang, Y. Y. Feng, T. C. Li, and L. J.
Wang, Sci. Rep. 2, 556 (2012).
2. C. Gao, B. Wang, W. L. Chen, Y. Bai, J. Miao, X. Zhu, T. C. Li, and L. J. Wang, Opt. Lett. 37,
4690-4692 (2012).
3. G. Grosche, “Verfahren zum Bereitstellen einer Referenz-Frequenz”, DPMA Patent application DE
10 2008 062,139 (June 24, 2010).

Novel Frequency Sources
CLUB D
Thursday, July 25 2013, 08:30 am - 10:00 am
Chair:

Michael Tobar
The University of Western Australia

IFCS-EFTF2-K3-1

Spintronics rf nano-oscillators based on spin transfer induced
dynamics of vortex magnetization
E. Grimaldi1, V. Cros1, P. Bortolotti1, A. Dussaux1, J. Grollier1, A. Fukushima2, H. Kubota2, K.
Yakushji2, S. Yuasa2, A. Fert1
1

Unité Mixte de Physique CNRS/Thales, Palaiseau, and Université Paris-Sud, Orsay/France
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba/Japan

2

Email: vincent.cros@thalesgroup.com

Noise spectrums (dBc/Hz)

A decade after the first observation of spin transfer (STT) induced magnetization dynamics, tremendous
improvements have been achieved for the rf characteristics of spin transfer nano-oscillators (STNOs).
Depending on the magnetic configuration and device shape, the emitted frequency goes from 100 MHz
up to 50GHz, thus making them promising for integrated telecommunication devices489. The key
advantages of these spintronics devices are their
Phase noise
500 nmlarge frequency tunability, their nanoscale size and50
Amplitude noise
their CMOS compatibility, and finally their
NiFe (5nm)
insensitivity to radiations. STNOs are by nature0highly nonlinear oscillators. The understanding of
MgO
10log(1+²)
the large coupling between phase and amplitude isSAF-50
thus crucial490 either to increase the role of491
10log(f0/2fp)
nonlinearities to improve the tunability
or tocancel the coupling when a stable reference signal-100
fpwith large spectral purity is targeted492.
2
3
4
5
6
Here we focus on STNOs based on vortex
10
10
10
10
10
107 108
Frequency from carrier (Hz)magnetization motion in a magnetic tunnel junction
made of NiFe (5nm) / MgO (1nm) / Ferromagnetic
polarizer (SAF) to investigate this coupling from Fig. 1 Phase (grey dots) and amplitude
phase and amplitude noise PDS measurements (black dots) noise PDS in dBc/Hz for an(Fig.1). In parallel, we derive nonlinear equations external magnetic field of 4.8 kOe and aofthe vortex dynamics493 in the general framework current of 3.3 mA. Inset: schema of thefortunneljunction
nonlinear oscillators494. We find that the phase noise ismagnetic
due to both
intrinsic
phase noise and conversionof amplitude noise into phase noise proportional to the coupling. By the extraction of the parameters andof their dependencies with current and magnetic field, we show that the intrinsic linewidth of the vortex
based oscillator is of tenth of kHz which is promising for future applications.
We acknowledge CANON ANELVA for preparing the MTJ ﬁlms. This work was supported by the
ANR through SPINNOVA P2N and EU grant MOSAIC FP7- N°317950. E.G. acknowledges financial
support from CNES and DGA.

489

J.A. Katine, E.E. Fullerton, J. Magn Magn. Mat. 320, 1217 (2010)
M. Quinsat et al., Appl. Phys. Lett. 97, 182507 (2010), L. Bianchini et al., Appl. Phys. Lett. 97, 032502 (2010)
491
A. Dussaux et al., Nat. Comm. 1, 8 (2010)
492
N. Locatelli et al., Appl. Phys. Lett. 98, 062501 (2011)493
A. Dussaux et al., Phys. Rev. B 86, 014402 (2012)
494
A.N. Slavin and V. Tiberkevich , IEEE Trans. Magn. 45, 1875 (2009)
490

IFCS-EFTF2-K3-2

Recent Progress and Perspectives of Extremely Low Loss
Acoustic Cavities: From Frequency Sources to Artificial Atoms
Maxim Goryachev1, Michael Tobar1, Serge Galliou2
1

ARC Center of Excellence for Engineered Quantum Systems, School of Physics, The University ofWestern Australia, 35 Stirling Highway, Crawley 6009, Australia
2
FEMTO-ST (UMR CNRS 6174), Département Temps Fréquence
ENSMM 26, Chemin de l’Epitaphe, 25000 Besançon, France
Email: maxim.goryachev@uwa.edu.au

In record low loss regimes at low temperatures495, Bulk Acoustic Wave quartz resonators could be
regarded as acoustic version of famous optical Fabry-Pérot cavities. Indeed, confining phonons in a plateof piezoelectric material is analogous to confining photons between two mirrors. In acoustic resonators,
the small volume conﬁnement, high phonon density, and long phonon storage time induce a very strongwave-matter and wave-wave interactions. The current state of affairs suggests that high-quality
cryogenic BAW resonators could be a new platform for many physical experiments and systemsimultaneously being a mechanical resonator and a phonon cavity.
The latest results demonstrate the ability of such devices to have quality factors of above one billion forfrequencies up to 400 MHz, and a hundred of million up to 720 MHz. Such results are achieved forvery-high overtones (up to 227th) of the longitudinal mode never observed previously.
We briefly discuss basic requirements to achieve extremely high quality factor regimes in acoustic
devices discussing main sources of losses. This includes material (two-level system, thermoelastic,
Landau-Ruomer losses), surface, design (effective phonon) requirements. Several types of BAW quartz
resonators are compared.
Finally, we discuss a range of application of extremely low loss acoustic cavities varying from designingof cryogenic ultra-stable frequency sources to creation of artificial atoms. On one hand, very narrow
bandwidths of the cavities (of orders of tens of miliHz) can be exploited to build frequency
discriminators for ultra-stable clocks at frequencies close to the laboratory standard (10 MHz). On
another hand, high overtones with frequencies above 300 MHz can be cooled down to the ground statewith conventional methods (down to 10mK with dilution refrigerators). So, BAW devices have aconsiderable advantage over traditional mechanical resonators like micro-toroids and membranes which
require additional cooling techniques (parametric, sideband cooling). By coupling acoustic cavities tononlinear elements like Josephson Junctions, quantum bits with extremely high coherence times could
be designed. In addition, piezoelectric nature of a cavity can be exploited to create strong photonphonon coupling regimes of a hybrid systems.

495

M. Goryachev et al, “Extremely low-loss acoustic phonons in a quartz bulk acoustic wave resonator at millikelvintemperature”, Appl. Phys. Lett. vol. 100, 243504, 2012.

IFCS-EFTF2-K3-3

A Novel Evanescent-Mode Mobius-Coupled Resonator Oscillators*Ajay K. Poddar, Ulrich L. Rohde,
University of Cottbus, BTU Cottbus 03046, Germany*Synergy Microwave Corp., Paterson, NJ 07504, USA
Email: akpoddar@synergymwave.com
A novel Mobius-coupled printed resonator oscillators reported in thispaper for the application of synthesized signal sources in RADAR andmodern microwave communication systems. The concept of the Mobius
strips is based on the fact that a signal coupled to a strip shall not
encounter any obstruction when travelling around the loop, enables
compact high Q-factor resonators. A necessary and sufficient condition
for a Mobius surface to be developable is that its Gaussian curvature
should everywhere vanish. Given a curve with non-vanishing curvature
there exists a unique flat ruled surface (the so-called rectifying
developable) on which this curve is a geodesic curve (Figure 1) is
described by [1](1)(2)

Fig. 1 A typical block diagram of 10.24 GHz MCEM VCO

Where is a parameterization of a strip with r as centerline and oflength L and width 2w, where is the unit tangent vector, the unit
binormal, k the curvature and τ the torsion of the centerline, theparameterized lines s = const. are the generators, which make an angle β= arc[Tan(1/η)] with the positive tangent direction. The unique propertiesof Mobius strips, the shape minimizes the deformation energy, which isentirely due to bending, can be described by(3)
where D =2h3E/[3(1-v2)], with 2h the thickness of the strip, and E andν Young’s modulus and Poisson’s ratio of the material. In this paper, aplanar Mobius-coupled resonator oscillator is described, and the method
for miniaturization can be applied to tunable filters, antenna andmatching networks.
Mobius-Coupled Evanescent-Mode (MCEM) resonators are attractive
due to several reasons: the Mobius effect makes them very compact and Fig.2 Measured quality factor (Q) of the Mobius coupled resonator
can support evanescent mode coupling for obtaining Q-multiplier effectat resonant condition, thus low phase noise signal source solutions.
Figure1 shows the block diagram and layout of the VCO using MCEM
resonators resonator fabricated on low loss RF dielectric substratematerial with a dielectric constant of 3.38 and thickness of 22 mils
printed structure. Figure (2) shows the measured plot of unloaded Qfactor of MCEM, acts like a Q-multiplier, peaking at 10GHz due toevanescent- mode-coupling. Figure (3) shows the measured phase noiseplot: –110dBc/Hz @ 10 kHz offset) from the carrier frequency of 10.24
GHz, which is best phase noise performance reported to date for a given
size (0.3x0.3 inches) in planar form.
References:[1] Starostin E.L., van der Heijden G.H.M. (2007). "The shape of a
Möbius strip". Nature Materials 6 (8): 563–7. doi:
10.1038/nmat1929.PMID 17632519.
[2] J. M. Pond, “Mobius Dual Mode Resonators and Bandpass Filter”,
IEEE. Trans. of MTT Vol. 48, Dec 2000, pp 2465-2471.
[3] J.M.Pond, S.Liu, and N.Newman, "Bandpass Filters Using DualMode and Quad-Mode Mobius Resonators," IEEE Trans. on Microwave Theory and Tech. vol.49, pp.2363-2368, Dec.2001.
Fig.3 Measured phase noise plot of 10.24 GHz MCEM VCO

IFCS-EFTF2-K3-4

Design of Ultra-Low-Power (2.5µW) 1GHz Low Phase Noise Pierce
Oscillator with Nanowire NEMS Resonator
Hamidreza Zamani1, Philip X.-L. Feng1
1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44016, USA
Email: hamidreza.zamani@case.edu.edu, philip.feng@case.edu

Laterally-vibrating nanowire (NW) resonators with high resonance frequencies fres and electrostatictransduction method are interesting for CMOS timing circuits. However, their motional resistance Rm isoften very high, much larger than their rivals FBARs with Rm of several ohms. Since Rm is also
proportional to the resonance frequency fres, design of high frequency oscillators are even more difficult.
In Pierce oscillators, the minimum MOS transconductance which makes oscillation feasible is496(parameters are identified in Fig. 1a). In this work, we propose and develop a
modified architecture using two small (bondwire) inductors (also connecting the nodes to DC bias
voltages) which reduce the effective motional resistance seen by the CMOS circuit. The analysis
includes novel analytical formulas for design of these modified Pierce-family oscillators working withresonators of initially high-motional resistance. As a proof of concept, we have provided Spectre
simulation results for a 1GHz oscillator with very low power consumption while having high voltage
amplitude at the output (drain of transistor M in Fig. 1a). The mechanical resonator assumed for thissimulation is a doubly-clamped Si NW with length, width, thickness and quality factor of respectively
419nm, 20nm, 80nm and 2000. Phase noise and spectral purity performance results are also provided.
The specifications in this work are compared to several recent related works. The specifications
reported in the Table for other works are measurement results.

Rm

Lm

Cg
C3

C′ 3

RBIAS
M

700mV

Lwirebond=1nH
C1C2
IBIAS=
100nA

067.319 dB

VDD=1.5 V

1.5
1.0

Phase Noise (dBc/Hz)

VDD=1.5VCm(c) -502.0

0.229 dBVpeak

Voltage Amplitude (V)Lwirebond=1nH

2V

0.5
0.0

-50

3.000

3.002
Time (s)-100-84 dBc/Hz-104 dBc/Hz

-100

-150

Phase Noise (dBc/Hz)

(b)

900mV

Peak Amplitude (dBV)

(a)

-100

-157 dBc/Hz
-150

-200

0

1

2

3
4
5
6
Frequency (GHz)78-200 2
10

1.020

1.025
Frequency (GHz)

1.030

3

4

5

6

10
10
10
10
Offset Frequency (z)7

10

Fig. 162: (a) Schematic of a 1GHz modified Pierce oscillator. (b) Spectral response of the oscillator harmonics compared to
the fundamental one. Inset: Oscillator output voltage in time domain (not connected to 50Ω load). (c) Phase noise simulation
results for offset frequencies around the major oscillation frequency (fosc=1.0256 GHz). Inset: Phase noise in a linear(absolute) frequency scale. The frequency resolution of sampling in the inset is lower, which causes difference in the phasenoise for frequencies very close to fosc.
This work[Zuo-CICC]497[Zuo-TUFFC]498[LavasaniISSCC]499

496

Rm
13.1MΩ
22Ω
25Ω
750Ω

fosc [GHz)
1.026
1.5
1.05
1.006

Pcon
2.5µW
6.9mW
3.5mW
1.9mW

Phase Noise [dBc/Hz]-84 (@1kHz), -104 (@10kHz), -157 (@1MHz)-85 (10kHz), -151 (@1MHz)-81 (@1kHz)-94 (@1kHz)

E. Vittoz, Low-Power Crystal and MEMS Oscillators: The Experience of Watch Developments, Springer 2010.
C. Zuo, J. Van der Spiegel, G. Piazza, “1.5-GHz CMOS…”, CICC2010, San Jose, CA, 2010.
498
C. Zuo, J. Van der Spiegel, G. Piazza, “1.05-GHz CMOS…”, IEEE Trans. UFFC, vol. 57, no. 1, p. 82-87, 2010.
499
H. H. M. Lavasani, W. Pan, B. Harrington, R. Abdolvand, and F. Ayazi, “A 76dBOhm, 1.7 GHz, 0.18um CMOS tunabletransimpedance amplifier…”, ISSCC 2010, San Francisco, CA, Jan. 2010, p. 318-320.
497

Lattice Clocks II
CLUB HThursday, July 25 2013, 10:30 am - 12:00 pm
Chair:

Patrick Gill
National Physical Laboratory

IFCS-EFTF6-L1-1

Optical lattice clocks near the QPN limit: A tenfold improvementin optical clock stability
Travis L Nicholson1, Michael J Martin1, Jason R Williams1, Benjamin J Bloom1, Michael Bishof1,
Matthew D Swallows2, Sara L Campbell1, and Jun Ye1
1

JILA, University of Colorado, Boulder, CO USA
2
AOSense, Sunnyvale, CA USA
Email: nicholtl@jilau1.colorado.edu

-16

10

-17

Exc. Frac.

Up to now lattice clocks with ~1000 atoms have notshown improvement over the stability of single-ion
clocks. Lattice clock stability has been limited bylaser noise (via the optical Dick effect). To address
this problem, we constructed a new clock laser with athermal noise floor of 1×10-16—an order of magnitudeimprovement over our previous clock laser. With thislaser, we compare two lattice clocks, reaching
instability of 1×10-17 in 2000 s for a single clock. Thisinstability is within a factor of 2 of the theoretical
QPN limit for ~1000 atoms, representing the lowest
reported instability for an independent clock502.

Allan Deviation

Two classes of optical atomic clocks have surpassed microwave frequency standards: single-ion clocks
and optical lattice clocks. Single-ion clocks hold the record for the lowest systematic uncertainty500;
however, many-atom lattice clocks501 have the potential to outperform single-ion clocks because thestandard quantum limit to atomic clock instability (known as quantum projection noise or QPN) scalesas (1/Natoms)1/2. For realistic atom numbers andcoherence times, QPN-limited lattice clocks could
Comparison Data
average down to a given stability hundreds of times
Dick Effect + QPN
QPN
10faster than the best ion clocks.
0.8
0.6
0.4
0.2
0

10

0

-10

0

10

Detuning (Hz)

10

1

10

2

10

3

Averaging Time (s)Fig. 163: A comparison between two independent
Sr optical lattice clocks. The stability is 4.4×1016 1/2/τ . The inset depicts typical scans of the clocktransition (open circles), and the red line is a fit to
the data using the Rabi model.

The high stability of many-particle clocks can come at the price of larger systematic uncertainty due to afrequency shift from atomic interactions. To minimize this shift, we use a cavity-enhanced lattice503 forour second clock. The high circulating power inside the cavity allows for a large trap volume, yielding adensity at 2000 atoms that is 27 times smaller (than in our first clock) and permitting us to trap as manyas 5×104 atoms. For 2000 atoms in our lattice, we measure a value for this shift (which is linear indensity) of -3.11×10-17 with an uncertainty of 8.2×10-19.

500

Chou, et al., PRL 104, 070802 (2010)

501

Ludlow, et al., Science 319 1805 (2008)

502

Nicholson, et al., PRL 109, 230801 (2012)503

Westergaard, et al., PRL 106, 210801 (2011)

IFCS-EFTF6-L1-2

Comparison of Sr optical lattice clocks at the 10-16 level
Jérôme Lodewyck, Chunayn Shi, Ulrich Eismann, M. Gurov, Rodolphe Le Targat
Y. Le Coq, J. Guéna, M. Abgrall, P. Rosenbusch, D. G. Rovera, S. Bize, P. Laurent.
LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France
Email: jerome.lodewyck@obspm.fr

In this paper, we present a comprehensive set of high resolution comparisons between opticallattice clocks using strontium atoms and three microwave cesium fountains. Two strontium opticallattice clocks are in agreement with a relative frequency difference of 1.1×10-16 between the two
apparatuses, compatible with the combined accuracy budget of 1.6×10-16, and a statistical resolution of
2×10-17, reached after a few hours of measurement.

This is the first comparison between two optical lattice clocks at a level beyond what can be achieved bycomparing optical clocks through microwave standards. It is a necessary step to confirm the establishedaccuracy budget of these clocks.
The comparison of these clocks with three state-of the art microwave fountains gives a reproducible
measurement of the absolute frequency of the Sr clock transition with respect to the SI second. Itfeatures record stability (limited by the Quantum Projection Noise of the microwave standards) andaccuracy (3.1×10-16).
The consistent set of optical-to-optical and microwave-to-optical clock comparisons presented here is a
step towards a possible redefinition of the second with optical references.
Finally, we will discuss prospects for improving the accuracy and stability of strontium optical latticeclocks.

1

R. Le Targat et al., “Experimenting an optical second with strontium lattice clocks”, arXiv:1301.6046 (2013)

IFCS-EFTF6-L1-3

s-Wave Collisional Frequency Shift of a Fermion Clock
Eric L. Hazlett1, Yi Zhang1, Ronald W. Stites1, Kurt Gibble1 and Kenneth M. O’Hara1
1

Department of Physics, The Pennsylvania State University, University Park, PA, USA
Email: kgibble@psu.edu

We have observed the s-wave collisional frequency shift of an atomic clock based on fermions504. As
T0, only s-wave collisions are allowed. While s-wave collisions are allowed for bosons and are themost important limitation for the operation of Cs fountain clocks505,506, they are forbidden for identicalfermions. Even when dephasing made fermions distinguishable, collision shifts were absent507. Thus,
fermions were thought to be immune to s-wave collisional frequency shifts (sCFS's), making them ideal
for metrology. However, recent theoretical work predicted that fermions have sCFS’s because excitation
field inhomogeneities make particles distinguishable508.
Here we experimentally observe s-wave collisional frequency shifts in a thermal gas of ultracold 6Li
fermions. Working near a Feshbach resonance, we tune the s-wave scattering length through 0 around
528G. Ramsey spectroscopy clearly distinguishes the novel behaviors of the sCFS, via uniquedependences on the first and second Ramsey pulse areas, q1 and q2. We demonstrate that the shift isinsensitive to q1 and thereby the difference of the spin populations508, in stark contrast with the shifts forbosons and the often-used mean-field expression. Instead, the fermion sCFS depends strongly on q2,
which reads out the interaction-induced phase shifts of each atom. The shift is canceled if the atoms'
phases are detected, on average, with equal sensitivity at q2=/2.508 Interestingly, we show that
correlations in the sample perturb the null of the sCFS to q2 slightly greater than /2. We explicitly seethat the sCFS increases as expected with the independently characterized inhomogeneity of the clock
field. The fermion sCFS we observe in the resolved sideband regime is analogous to those for opticallattice clocks. Recently, the fermion sCFS was simulated with an 87Rb Bose gas509. They observed thepredicted dependence on q2, but an unexpected dependence on q1. They elegantly showed a direct link
between spin-waves and the fermion sCFS, which we observe in the resolved sideband regime.

504

E. L. Hazlett, Y. Zhang, R. W. Stites, K. Gibble and K. M. O’Hara, “s-Wave Collisional Frequency Shift of a Fermion
Clock,” submitted to Phys. Rev. Lett. (arXiv:1212.4385).

505

K. Gibble and S. Chu, "Laser-Cooled Cs Frequency Standard and a Measurement of the Frequency Shift due to Ultracold
Collisions," Phys. Rev. Lett. vol. 70, p. 1771-1774, 1993.

506

R. Li, K. Gibble and K. Szymaniec, “Improved accuracy of the NPL-CsF2 primary frequency standard: evaluation of
distributed cavity phase and microwave lensing frequency shifts,” Metrologia vol. 48, p. 283-289, 2011.

507

M. W. Zwierlein, Z. Hadzibabic, S. Gupta, and W. Ketterle, “Spectroscopic insensitivity to cold collisions in a two-state
mixture of fermions,” Phys. Rev. Lett. vol. 91, p. 250404, 2003.

508

K. Gibble, “Decoherence and Collisional Frequency Shifts of Trapped Bosons and Fermions,” Phys. Rev. Lett. vol. 103,
p. 113202, 2009.

509

W. Maineult, C. Deutsch, K. Gibble, J. Reichel, and P. Rosenbusch, “Spin waves and Collisional Frequency Shifts of aTrapped-Atom Clock,” Phys. Rev. Lett. vol. 109, p. 020407, 2012.

IFCS-EFTF6-L1-4

An Yb optical lattice clock: Current status at KRISS
Dai-Hyuk Yu, Chang Yong Park, Won-Kyu Lee, Sangkyung Lee, Sang Eon Park, Sang-Bum Lee,
Jongchul Mun, Myoung-Sun Heo, and Taeg Yong Kwon
Korea Research Institute of Standards and Science, Daejeon, Rep. of Korea
Email: dhyu@kriss.re.kr
Current status of an Yb optical lattice clock at KRISS will be reported. The systematic uncertainty of the
Yb clock in the first accuracy evaluation510 was 510-14. The uncertainty was dominated by the large
uncertainties in the lattice ac Stark shift and collisional shift, which were mainly limited by the large
linewidth and jitter of the clock laser. Recently, highly stable clock laser at 578 nm was developed witha short-term linewidth of 3.5 Hz and frequency jitter of about 25 Hz at 1 s, and 10 s measurement time,
respectively. Long-term frequency drift showed only linear dependence on time confirming that thetemperature of the super-cavity is maintained at the zero in the coefficient of thermal expansion of thecavity. The frequency of the lattice laser at 759 nm was phase locked to the optical frequency comb andit could be stabilized at the “magic wavelength” within 1 MHz uncertainty. With these and otherimprovements, new accuracy evaluation is underway and the results will be presented.

Fig. 164: Experimental setup for the frequency stabilization of the 759 nm laser by using the opticalfrequency comb and measured beat frequency after stabilization.

510

C. Y. Park, et al., “Absolute frequency measurement of 1S0(F = 1/2)–3P0(F = 1/2) transition of 171Yb atoms in a onedimensional optical lattice at KRISS”, Metrologia, vol. 50, p. 119-128, 2013.

IFCS-EFTF6-L1-5

Nonlinear and Anharmonic contributions to Uncertainties of
Optical Clocks on Ultracold Alkaline-Earth-Like Atoms
Vitaly Ovsiannikov1 and Vitaly Palchikov2
1

2

Voronezh State University,394006 Voronezh, Russia
FGUP “VNIIFTRI”, 141570 Mendeleevo, Moscow Region,Russia

Email: vitpal@mail.ru
The progress in designing optical frequency standards with unprecedented fractional frequency
uncertainty at a level 10-17 – 10-18 requires unprecedented accuracy in estimating the role of different
uncertainties of optical clocks511.
In this paper, we systematically evaluate various sources of
uncertainty for the alkaline-earth-like-based optical lattice clocks either on odd isotopes or on evenisotopes.
The method of determining “magic wavelength”1, based on measuring the shift of the clock frequency ina weak field of a travelling wave2 accounts for the Stark shift of energy levels, but only linear in thelaser intensity, with inclusion of all multipole-interaction terms. However, the spatial distributions ofmultipole components in a lattice-atom interaction is not uniform, therefore higher multipole ac Stark
shifts are a quarter wavelength out of phase with the electric dipole shift . In a 1D red-shifted MWL
lattice, the first-order in the laser-wave intensity I (second order in the electric-field amplitude2
E0  1.68862 107 I , where E0 is measured in atomic units and I is in kW/cm ) clock frequency shift
has a spatial distribution, as follows: cl   E0 cos (km X )   E0 sin (km X ) ,
( 2)

E1

2

2

qm

2

2

(1)

where km  2 / m is the wave number and    ( )   ( ) , X is the coordinate along the latticeaxis, with the origin in the minimum of the lattice well.
High intensity of the lattice wave makes considerable the contribution of quadratic in I terms,
determined by the atomic hyperpolarizabilities  e ( g ) (m ) :
(2)
Ee(4)
 1/ 4   e ( g ) (m )E04 cos 4 (km X ) .
(g)
This term gives quadratic in I contribution to the atomic position-independent shift of the standard
frequency. After averaging over the atomic oscillatory motion, the position-dependent part of thestandard-frequency shift transforms into a term proportional to I 3/ 2 , while anharmonic-interaction termtransforms into linear in I shift. A significant advance of a lattice with a blue-shifted “magic
wavelength” consists in elimination of a position-independent quadratic shift and transformation of
hyperpolarizability effects into linear in I , which may be compensated by a slight redefinition of thelattice-laser frequency.
e

1
2

m

g

m

M. Takamoto, et al.,, “An optical lattice clocks,” Nature, vol. 435, p. 321-328, 2005.
G.Takamoto et al., “Prospects for optical clocks with a blue-detuned lattice,” Phys.Rev.Lett., vol. 102, p. 063002, 2009.

Geodesy and Radio Astronomy
CLUB E
Thursday, July 25 2013, 10:30 am - 12:00 pm
Chair:

Demetrios Matsakis
US Naval Observatory

IFCS-EFTF5-L2-1

On the Importance of Time and Frequency in Geodesy
Ulrich Schreiber1
1

Forschungseinrichtung Satellitengeodaesie,
Technische Universitaet Muenchen,
Muenchen, Germany
Email: schreiber@fs.wettzell.de

According to Friedrich Robert Helmert geodesy is the science of the measurement and mapping of the
figure of the Earth. With the advent of the space age it was possible to establish a global reference
frame, which can relate different locations across the entire Earth with an accuracy of currently about 1
cm with respect to each other. A rapid development of highly precise and stable frequency standards
took place at the same time and is an important prerequisite for the actual quality of this global terrestrialreference frame. Therefore all measurement techniques in modern space geodesy are based on precise
time and frequency. Growing demands for the monitoring of global change as one of several examplesof the importance of a highly resolved reference frame require more than one order of magnitudeimprovement over the existing level of quality. Optical clocks, optical frequency combs and near
lossless time and frequency transfer have the potential to provide significant improvements of theindividual techniques of space geodesy. This talk reviews how time and frequency impacts space
geodesy and how the observation techniques may benefit from the recent progress in this field.

IFCS-EFTF5-L2-2

A Fiber Optic Gyroscope on multiplexed telecommunication
network with a large enclosed area
C. Clivati1,2, D. Calonico1, G. A. Costanzo1,2, A. Mura1, M. Pizzocaro1,2, F. Levi1
1

Istituto Nazionale di Ricerca Metrologica, Torino, Italy
2
Politecnico di Torino, Torino, Italy
Email: c.clivati@inrim.it

Optical gyroscopes exploiting the Sagnac effect are currently used as optical rotation sensors. Two kindsof devices exist: Fiber Optic Gyroscopes (FOGs) are used in several commercial applications, being
very reliable and robust. They are limited by shot noise and typically achieve resolutions of ~10-6 rad/s1.
On the converse, Ring Laser Gyroscopes achieve higher resolution, being able to detect rotation signals
well below 10-9 (rad/s)/√Hz. They are thus attractive for a detailed study of rotational ground motion
induced by teleseismic waves2,3. However, they are complex experiments using sophisticated optics.
To combine a simple and robust setup with highInternet Data Traffic
Phase modulation
OADM1
resolution, we realized a FOG enclosing a
20
AOM1
CCW
20 km
CW
km2 area4 on a 47 km fiber. The fiber is used for thePS
LASER
CW+CCW
C1
C2+Internet
Data
Traffic
internet data traffic and has a Dense Wavelength
Not usedCW
CW+CCW
CCW
AOM2
OADM2
Division Multiplexed architecture. The setup is thePD
Frequency
Internet Data TrafficRFsame as for passive FOGs (see Fig. 1). A laser beam
Modulation
990 kHz LO
Feedback Loopis split into two beams that travel over the loop in
opposite directions, acquiring a phase shift that
Fig. 165: Setup of the FOG. PS polarization
depends on the Earth rotation. After a round trip, the scrambler, C couplers, AOM acousto optic
two beams are recombined to detect the Sagnac modulators, OADM Optical Add&Dropphase. A well-known technique of non-reciprocal Multiplexers, CW(CCW) clockwise (counterphase modulation is used to this purpose. We clockwise) propagating beams.
developed a closed loop system in which thenonreciprocal phase is compensated inserting a small frequency offset between the two beams.
Thanks to its large area, this system could be suitable to detect variations in the Earth rotation rate with asensitivity of 10-8 (rad/s)/√Hz, limited by the non-reciprocal mechanical noise of the fiber.
2

At the conference we will present a description of our system, the results we obtained, and an analysis of
the present limitations and of possible perspectives of this technique, also in consideration of the present
widespread of phase-coherent optical links across large geographical areas.
1. A. Velikoseltsev, K. U. Schreiber, A. Yankovsky, J.-P. R. Wells, A. Boronachin, A. Tkachenko, “On the application ofﬁber optic gyroscopes for detection of seismic rotations“ J. Seismol. 16 , 623 (2012).
2. H. Igel, K. U. Schreiber, A. Flaws, B. Schuberth, A. Velikoseltsev, A. Cochard, “Rotational motions induced by the M 8.1
Tokachi-oki earthquake, September 25, 2003”, Geophis. Res. Lett. 32 , L08309 (2005).
3. J. Belﬁ, N. Beverini, G. Carelli, A. Di Virgilio, E. Maccioni, G. Saccorotti, F. Stefani, A. Velikoseltsev, “Horizontal
rotation signals detected by “G-Pisa” ring laser for the M=9.0, March 2011, Japan earthquake”, J. Seismol. 16, 767 (2012).
4 C. Clivati, D. Calonico, G. A. Costanzo, A. Mura, M. Pizzocaro, F. Levi “A Large Area Fiber Optic Gyroscope on
multiplexed fiber network”, accepted for pubblication in Opt. Lett.

IFCS-EFTF5-L2-3

Optical fiber-based radio frequency signal transfer
and radio-astronomy applications
Yabai He,1,2 Magnus T.L. Hsu,1 Malcolm B. Gray,1 R. Bruce Warrington,1 Michael J. Wouters,1 Brian J.
Orr,2 Andre N. Luiten,3,4 Sascha Schediwy,4 Kenneth G.H. Baldwin,5 Tasso Tzioumis,6 Chris Phillips,6Guido Aben7 and Tim Rayner81National Measurement Institute, Sydney, Australia
2
MQ Photonics Research Centre, Macquarie University, Sydney, Australia
3
Institute of Photonics and Advanced Sensors, University of Adelaide, Australia
4
University of Western Australia, Perth, Australia
5
Research School of Physics and Engineering, The Australian National University, Australia
6
CSIRO Astronomy and Space Science, Sydney, Australia
7
AARNet, Perth, Australia
8
AARNet, Canberra, Australia
Email: Magnus.Hsu@measurement.gov.au
A collaboration between the National Measurement Institute (NMI) and a number of Australian
universities and research institutions has been working for several years to promote the construction of acontinental-scale optical-fiber network in Australia for the distribution of optical and microwave
reference frequencies. This network would connect a number of radio-astronomy sites and researchlaboratories with the NMI, allowing long-range comparison of frequency standards and dissemination ofhigh precision reference signals for a wide range of applications.
We have developed two systems for the distribution of microwave reference frequencies via opticalfiber; these systems have particular application to radio astronomy:(i)

One system implements algebraic cancellation of phase-noise in the link using analog radiofrequency (RF) electronics512. Recent results show transfer stabilities of 3 ×10–13 at 1 s and 6 ×10–
17
at 104 s over 175 km of optical fiber including two bidirectional optical amplifiers.

(ii)

The other system uses an all-digital architecture based on Field-Programmable Gate Arrayhardware513. Our published results reported radio frequency signal transfer with stabilities of 4
×10–13 at 1 s and 6 ×10–17 at one day over 70 km of optical fiber, with more than two orders ofmagnitude in fiber phase noise suppression.

We are now applying these methods to real-world optical fiber links. We report on the latest results on
our frequency transfer systems at CSIRO’s Australian Telescope Compact Array (ATCA) radiotelescope facility located at Narrabri, NSW. The ATCA consists of an array of six 22 m radio-antennas,
and can be operated as one site within a much larger Very Long Baseline Interferometry (VLBI) array.
Typically, each site in the VLBI array has a local hydrogen maser; our aim, therefore, is to replicate thislevel of stability by transferring RF signals over fiber.
Our latest results involving fiber-based distribution of a common RF signal through a practical fiber link
between two radio-antennae sites will be reported at the conference.
512

Y. He et al., “Long-distance analog and digital dissemination of reference radio frequencies over optical fibers”, 20th AIPCongress, Sydney, Australia (2012)
513

M.T.L. Hsu et al., “All-digital radio-frequency signal distribution via optical fibers”, IEEE Photonics Technology Letters24, 1015 (2012).

IFCS-EFTF5-L2-4

Ultra-Stable Oscillator Reference Spacecraft-to-Spacecraft
Links For Planetary Exploration
Sami Asmar1, Kamal Oudrhiri1, Gregory Weaver2
1

Radio Science Systems Group, Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, CA, USA
2Space Department, Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
Email: asmar@jpl.nasa.gov

Thermally controlled quartz crystal Ultra-Stable Oscillators (USO) have been utilized on deep space
missions for Radio Science experiments. Starting with the Voyager mission to the outer planets,
atmospheric science has benefited tremendously from the radio occultation technique enabled by USOs.
Recently, the GRAIL mission to the Moon, which applied the GRACE mission concept, utilized USOs
as part of the science payload to investigate the lunar interior structure. Identical USOs on twin
spacecraft flying in precision formation around the moon generated signals at X,- S-, and Ka-bands withthe latter two exchanged between the spacecraft and the former broadcast to Earth. With 2 parts in EE13 stability in the range of 10 to 100 second integration times, the USOs were precise enough tomeasure change in the range between the spacecraft (varied between 65 and 225 km) to the size of ablood cell. The velocity variations were measured to a few microns. This precision enabled the mission
to reach its scientific objectives with large margins reveling the lunar composition from the crust to thecore. Due to the low altitude of the mission and its duration, a gravitational field of the Moon in excessof 880 degree and order (spherical harmonic coefficients) was produced with a surface resolution of afew kilometers.
This paper will describe the roles of USOs in scientific discoveries in deep space with a brief historical
overview, recent technological advances and future trends. The scientific applications will be describedranging from atmospheric and ionospheric occultations, surface scattering, and precision Doppler forgravitational field measurements.

Fig. 166: Multiple radio links from the twin GRAIL
spacecraft, Ebb and Flow, referenced to on-board
Ultra-Stable Oscillators, utilized for precision
gravity measurements.

IFCS-EFTF5-L2-5

GRACE Kinematic Orbit Determination: the Role of Clocks
Etienne Orliac1, Adrian Jäggi1, Heike Bock1, and Rolf Dach1
1

Astronomical Institute, University of Bern, Bern, Switzerland

Email: etienne.orliac@aiub.unibe.ch

The processing of a global network of ground Global Positioning System (GPS) tracking stations allows
for the computation of orbits and clock corrections for the GPS satellites. This information provides thebasis for precise kinematic orbit determination for Low Earth Orbiting (LEO) satellites based on the datacollected with their onboard GPS receiver. One example are the twin satellites from the GRACE mission(Gravity Recovery And Climate Experiment), which carry highly stable onboard clocks.
The quality and consistency of the GPS satellite orbits and clock corrections is essential for the qualityof the obtained kinematic LEO positions. The high-rate satellite clock corrections are typicallycomputed using data from the International GNSS Service (IGS, GNSS standing for Global Navigation
Satellite System) in the three-step scheme: first, based on code and phase data, a global solution
containing all relevant parameters with a 5 minutes sampling is computed. For practical reasons the 5
minutes satellite clock corrections are interpolated down to 30 seconds using time differences of thecarrier phase observations. A further densification to 5 seconds is done again with a phase measurement
based interpolation but using a different set of stations (not all stations provide data with a samplinghigher than 30 seconds). For GRACE kinematic orbit determination, 10 seconds clock corrections areneeded.
We propose here to investigate the impact of the interpolation of the GPS satellite clock corrections on
the determination of GRACE kinematic orbits and clock parameters, and to eventually assess the impact
on subsequent gravity field recovery from the kinematic positions. We will vary the above described
scheme for clock corrections computation and assess the impact on the obtained GRACE kinematic
trajectories. Conventionally the receiver clock corrections are set up as epoch-wise independent
parameters. However, the GRACE onboard clocks are highly-stable, which may allow it to model theclock over a few epochs with a sufficient accuracy. To assess the benefit on the derived kinematic
positions, gravity fields are computed and compared with conventional solutions based on kinematic
positions with receiver clock corrections estimated epoch-wise.

MEMS Resonators
CLUB D
Thursday, July 25 2013, 10:30 am - 12:00 pm
Chair:

Bernard Dulmet
FEMTO-ST

IFCS-EFTF1-L3-1

CMOS-MEMS Resonators and Their Applications
Sheng-Shian Li
Inst. of NanoEngineering and MicroSystems, National Tsing Hua University, Hsinchu, Taiwan
Email: ssli@mx.nthu.edu.tw
In the past few years, the CMOS-MEMS technology has been thoroughly explored and implemented invibrating MEMS applications. This paper reports the recent progress on CMOS-MEMS resonators andtheir implementations in our group, as shown in Fig. 1. These resonators (Fig. 1a) were fabricated using
standard CMOS processes offered by foundry services, such as TSMC and UMC, to facilitate fast
prototyping, quick turnaround time, batch production, low cost, and monolithic integration. Specifically,
we take advantage of IC and semiconductor strength in Taiwan to develop several unique CMOSMEMS resonator fabrication platforms514515 targeted for inherent integration of MEMS and circuitry, asa result towards single-chip implementation for timing reference and filter applications.
In this paper, resonator performance enhancement in terms of motional impedance, power handlingcapability (Fig. 1b), linearity, quality factor, frequency tunability (Fig. 1c), temperature compensation(Fig. 1d), and feedthrough reduction (Fig. 1e) addressed by the use of our proposed active gap reduction
mechanism, mechanically-coupled array approach, bias-dependent electrical stiffness, oxide-type
structural material, and fully differential scheme, respectively, would be presented. In addition,
oscillator (Fig. 1f) and filter (Fig. 1g) implementations via these fabricated CMOS-MEMS resonators
will also be illustrated, showing their device characterization and measured performance.
In sum, the main contribution of our group is on the development of CMOS-MEMS-based highperformance resonator circuits. This technology is expected to pave a way to realize fully-integrated
CMOS-MEMS oscillators and filters which might benefit single-chip transceivers.

0Free-Free Beam∆f/fo [ppm]-10,000

Amplifiers-20,000
fo= 11.56MHz-30,000
fo= 3.96MHz-40,000

Comb
Drive

Transmission [dB](d)In Vacuum

-50

-70

(c)

(b)

(a)

-60

-∆- TCf ,composite =-65ppm/°C-O- TCf, mere metal =-358ppm/°C-50,000

Pull-in Frame

Coupler

-40

-20

0
20
40
Temperature [°C]6080

Meander Spring

Single-ended in & out
Feedthrough(30-dB)

Differential in/ Single-ended
out

vi

VO

VP

Diff. AMP
VR

VtSingle-ended in/Differential out

-80
-90

VD
VP=30 VPo= -10 dBm
Q= 950Rm = 349 kΩ
f0 = 9.4 MHz

Fully Differential

-100
-110

(e) 9.1

9.3

9.5

Frequency [MHz]

9.7

(f)

Diff. MEMS Res.

(g)

Driving
ElectrodeBeam-Array
Resonator

Sensing
ElectrodeFig. 167: (a) CMOS-MEMS integration. (b) Mechanically-coupled resonator array. (c) Frequency tuning.
(d) Temperature compensation. (e) Feedthrough reduction. (f) Oscillator and (g) filter implementation.
514

W.-C. Chen, W. Fang, and S.-S. Li, “A generalized CMOS-MEMS platform for micromechanical resonatorsmonolithically integrated with circuits,” J. Micromech. Microeng., vol. 21, no. 6, pp. 065012, May 2011.
515

W.-C. Chen, W. Fang, and S.-S. Li, “High-Q integrated CMOS-MEMS resonators with deep-submicron gaps and quasilinear frequency tuning,” IEEE/ASME J. Microelectromech. Syst., vol. 21, no. 3, pp. 688-701, June 2012.

IFCS-EFTF1-L3-2

2DEG Electrodes for Piezoelectric Transduction of AlGaN/GaN MEMS
Resonators
Laura Popa1, 2, Dana Weinstein2
Department of Physics, MIT, Cambridge, MA, USA
2
Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA, USA
Email: lpopa@mit.edu
1This work presents the use of two-dimensional electron gas (2DEG) interdigitated transducers (IDT) for
actuation of piezoelectric AlGaN/GaN MEMS resonators. Most piezoelectric resonators require
patterned metal electrodes which can limit the performance through mass loading, increased damping
and distortion of the mechanical mode. AlGaN/GaN heterostructures, increasingly used in millimeterwave ICs, enable metal-free, high-Q resonators. Fig. 1 (a) illustrates the sharp conduction band potential
well at the AlGaN/GaN interface which induces a high density, high mobility sheet of charge. This
2DEG can be patterned into IDTs by removing the AlGaN selectively (Fig. 1 b, c). 2DEG IDTs havebeen previously demonstrated in a SAW AlGaN/GaN filter516 but this work is the first implementationin MEMS resonators.
Metal-free resonators can be used to directly interrogate GaN material properties in the absence of loss
associated with metal electrodes. In Fig. 2, measured frequency response of 2DEG IDT bulk acoustic
wave resonator shows a 1.225 GHz shear vertical mode, coupled with thickness shear. Measured Qload is1180 and f.Qload product 1.44×1012, comparable to the highest in GaN2. Generally, Q factors are limited
by dissipation mechanisms such as inelastic phonon scattering, thermoelastic damping, air damping,electrical and anchor losses. Here, testing is performed in vacuum, to minimize air damping, whilequarter-wavelength matched suspension beams reduce anchor loss. By accounting for the parasitic series
resistance of the 2DEG electrodes, the intrinsic mechanical Qmech of the resonator is extracted to be
1290, giving an f.Qmech product of 1.58×1012.

Fig. 1. (a) Conduction band potential well at AlGaN Fig. 2: Measured frequency response of metal/GaN interface gives rise to conductive 2DEG. (b) free IDT resonator with 2DEG electrodes after
2DEG is removed in the regions where AlGaN is deembeding with an open structure. Inset
etched. (c) SEM shows resonator with 2DEG IDT. shows out of plane displacement of 1.225 GHz
Ohmic metal makes contact to 2DEG off the resonator. resonant plate.
516
2

K.-Y. Wong, K. Chen, et. al., Applied Physics Letters, vol 90, 213506 (2007).

A. Ansari, M. Rais-Zadeh, et. al., IEDM, 485-88 (2011).

IFCS-EFTF1-L3-3

REDUCTION OF ANCHOR LOSSES BY ETCHED SLOTS IN ALUMINUM NITRIDECONTOUR MODE RESONATORS
Cristian Cassella1, Massimiliano Cremonesi2, Jeronimo Segovia1,Attilio Frangi2,Gianluca Piazza1
1

Carnegie Mellon University, Pittsburgh, PA, USA
2
Politecnico of Milan, ITALY
The replacement of Quartz crystals and surface-acoustic wave devices by CMOS-integrable MEMS
resonators requires simultaneously achieving high quality factors, Q, and high electromechanicalcoupling coefficients, kt2.AlN MEMS contour-mode resonators (CMR) have emerged as promising
candidates, and exhibited kt2 in excess of 1% and Qs of ~ 2000 from 100 MHz to 1 GHz. It has beenshown experimentally that the main dissipation mechanisms in AlN MEMS piezoelectric resonators are
related to anchor and interfacial losses [1,2]. The former depends on acoustic energy escaping theresonator and being dissipated into the substrate; the latter arises from stress discontinuity at theinterface between different materials and becomes dominant at frequencies in excess of 500 MHz [3].
In this paper, a new technique for reducing the anchor losses and correspondingly increasing the Q in
220 MHz AlN CMR devices is presented. The technique is based on the introduction of etched slots
inside the body of the AlN resonant structure, in close proximity of the anchor location. The air slot
acts as an acoustic reflector and reduces the energy lost into the substrate. Different dimensions of theetching slot have been investigated (see Fig. 1) and two sidewall angles for the AlN film were analyzed(30 and 60 degrees as defined in Fig. 1). A Q enhancement up to 50% was attained for an etching slot
having a width equal to 0.35 times the acoustic wavelength. An analytical model that describes the
expected improvement in Q varying the slot width was also developed. As shown in Fig. 2 the predicted
trend follows the experimental results and is in line with the Finite Element Analysis code that wasdeveloped to predict anchor and surface dissipation in AlN MEMS resonators [3].

Figure 168: Geometry of 220 MHz resonators (λ≈40Figureum) 2: Red points ( ): measured Q for
A,B,C,D (θ=30 degrees).
in 4 configurations (A, B, C, D) where the slot widthconfigurationsWe
has been varied (0,3,7,14 um). Two different sidewall
Yellow
points( ):measuredQ
forangles have been investigated (30 degrees and 60 degrees).
configurations A,B,C,D (θ=60 degrees).
SEM pictures of the etching slot for configuration B , C, D continuous line: analytical model for Q
Green
are also shown.
varying We (θ=30 degrees). Purple dotted

line: analytical model for Q varying We(θ=60 degrees). Orange points( ): FEM
simulation of Q for A,B,C (θ=30 degrees).

IFCS-EFTF1-L3-4

A 2.8 GHz Combined Mode of Vibration Aluminum Nitride MEMS
Resonator with High Figure of Merit Exceeding 45
Yu Hui, Zhenyun Qian and Matteo Rinaldi
Department of Electrical and Computer Engineering, Northeastern University, Boston, MA/USA
Email: hui.y@husky.neu.edu, rinaldi@ece.neu.edu
This paper presents the first demonstration of a high frequency (2.8 GHz), lateral field excited (simple twomasks fabrication process), combined lateral-thickness extensional mode of vibration aluminum nitride(AlN) micro-electro-mechanical (MEMS) resonator with unprecedentedly high figure of merit (kt2Q > 45).
For the first time, a single interdigital electrode was employed to excite a high frequency mode of vibrationin an AlN plate (1.5 µm thick) by making use of both the d33 and d31 AlN piezoelectric coefficients517. The
resulting MEMS resonator showed high quality factor, Q~2000, (thanks to the high quality AlN film directly
deposit on top of the Silicon substrate) and the highest electromechanical coupling coefficient ever reported
for AlN MEMS resonators employing a single electrode, kt2~2.5% (thanks to the coherent combination of d33
and d31 coefficients to transduce one single mechanical mode of vibration).
The use of a single interdigital electrode to excite (lateral field excitation, LFE) a high frequency contourextensional mode of vibration in AlN microstructures has been previously demonstrated518. However, due tothe relatively low d31 coefficient of AlN, the maximum predicted electromechanical coupling coefficient519
for such class of devices is only 1.5%. In this work, by properly optimizing the ratio between the thickness of
the AlN film (t) and the pitch of the interdigital top electrode (Wp) the d33 and d31 coefficients have beencoherently combined and harnessed to transduce one single mechanical vibration mode. The combinedlateral-thickness mode of vibration was simulated using COMSOL showing a maximum value ofelectromechanical coupling coefficient, kt2 = 2.82%, for t/Wp0.94. A device with such optimum t/Wp was
fabricated (Fig. 1), showing high quality factor (Q = 1855) and a value of electromechanical coupling
coefficient (kt2 = 2.48%) ~2 times higher than what is typically achieved with conventional LFE AlN
contour-extensional mode resonators2 (Fig. 2).

Fig. 1: SEM image of the fabricated AlN
combined mode of vibration MEMS resonator.
t/Wp was set to be ~0.94, resulting in aresonance frequency of the 2.8 GHz. It is worth
noting that the fabricated device is fully
anchored to the substrate maximizing power
handling and minimizing electric loss due to517
C. J. Zuo, et al. IEEE IFCS 2012, pp. 1-4.
518 routing.
519

C. J. Zuo, et al. IEEE IFCS 2009, pp. 381-384.
J. H. Kuypers, et al. IEEE IFCS 2008, pp. 240-249.

Fig. 2: Measured admittance curve and BVD model
fitting of the fabricated AlN resonator. High device
figure of merit (FOM = kt2·Q = 46) and low
motional resistance (Rm = 15 Ω) were achieved at
2.8 GHz. The inset shows the 2D FEM simulationof the mode of vibration, indicating a combinedlateral-thickness extensional mode of vibration.

IFCS-EFTF1-L3-5

Highly coupled resonator based on ridge-shaped periodicallypoled materials for radio-frequency applications
Fabien Henrot1, Florent Bassignot1, Clément Guyot1, Jean-Yves Rauch1, Blandine Guichardaz1, Sylvain
Ballandras2
1

FEMTO-ST Institute, 32 avenue de l’Observatoire, 25000 Besançon, France
2
FreC'N'Sys, 18 rue Alain Savary, 25000 Besançon, France
Email: fabien.henrot@femto-st.fr

Most resonator and filters are based on Surface Acoustic Wave (SAW) technology using inter-digitatedtransducer (IDT). This mature technology is particularly addressing radio-frequency filter demand, but it
is limited by various factors. Recently, the interest of periodically poled transducer built on single
crystal LiNbO3 Z-cut plates was investigated as an interesting alternative to classical inter-digitaltransducers520. Performances of such a device were theoretically demonstrated showing many
advantages such as electromechanical coupling and equivalent phase velocity. This paper shows thepractical existence of high electromechanical coupling (k²=15%) and high phase velocity (10000m.s-1)
for this kind of transducer.
This new device has been modeled with our finite and boundary elements simulation tool for both
LiTaO3 and LiNbO3 to determine the most interesting design. LiNbO3 is known as highly coupledmaterial; LiTaO3 is used for its similar properties and shows a better coefficient temperature of
frequency. A high aspect ratio ridge-shaped transducer was made of LiNbO3 to show the resonatorcapabilities. The manufacturing process is achieved by dicing a ridge in a poled plate with a diamondtipped saw and plating the ridge walls to define the electrodes.
The dispersion properties analysis have shown one longitudinal mode (k²max=12%) and one shear mode
(k²max=22%) for a “ridge width/poling period” ratio of 0.4 and 0.2 respectively. A 500µm-deep andabout 120µm-wide ridge has been successfully fabricated on a periodically poled LiNbO3 exhibiting apoling period of 600µm. The device characterization shows an electromechanical coupling about 15%
and a difference between theoretical and experimental resonance frequencies under 1%. Parasitic effects
shown on fig. 1 (b) are caused by a parallelism defect of the ridge sides, which is the main problem tofix for future improvement.

a)b)Fig. 169: SEM view of ridge shaped transducer (a) and a comparison of theoretical (k²=22%) and experimental (k²=15%)
results (b)520

E. Courjon et al., “Lamb wave transducers built on periodically poled Z-cut LiNbO3 wafers”, vol. 102, 114107, 2007.

Optical Techniques
CLUB E
Thursday, July 25 2013, 02:00 pm - 03:30 pm
Chair:

Steve Lecomte
CSEM

IFCS-EFTF6-M1-1

Optical absolute frequency reference for space applications
Klaus Döringshoff1, Thilo Schuldt2,3,4, Johannes Stühler2,3, Evgeny V. Kovalchuk1,
Matthias Franz2, Ulrich Johann5, Claus Braxmaier3,4, Achim Peters1
1

2

Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
Institute for Optical Systems, University of Applied Sciences Konstanz, Konstanz, Germany 3Center
for Applied Space Technology and Microgravity (ZARM), University Bremen, Germany
4
DLR Institute for Space Systems, Bremen, Germany
5
Astrium GmbH – Satellites, Friedrichshafen, Germany
Email: Klaus.Doeringshoff@physik.hu-berlin.de

Future space missions related to fundamental science, Earth observation or navigation and ranging
require ultra-stable optical frequency references for the employed lasers. Setups based on saturation
spectroscopy of molecular iodine are well known frequency reference for Nd:YAG lasers, of whichspace qualified versions are available.
With the goal of a space qualified iodine frequency reference with 10−15 stability at 6000 s, we havedeveloped a compact ruggedized setup based on a 550 mm × 250 mm baseplate made of Clearceram-HS
glass ceramic with ultra-low coefficient of thermal expansion (Fig. 1). The optical elements are joint tothe baseplate using adhesive bonding technology with a space-qualified two-component epoxy. The
spectroscopy setup features a 30 cm iodine cell used in triple pass configuration of the counter
propagating pump- and probe beam, which are stabilized to 8 mW and 1 mW, respectively. Balanced
detection provides an excellent signal to noise ratio of the modulation transfer spectroscopy signal. As
laser source we employ a frequency doubled Nd:YAG laser. Frequency modulation of the pump beam isrealized via an acousto-optic modulator, where residual amplitude modulation is detected and cancelledin quadrature detection to avoid lock point errors. The laser is stabilized to the a10 component of thetransition R(56)32-0, and its frequency stability is determined from beat note measurements with acavity stabilized laser. The frequency measurements show a short term stability of 8 × 10−15 at 1 s
integration time averaging down to below 3 × 10−15 at 20 s (cf. Fig. 2).
In a current activity, an engineering model (EM) will be realized on a 380 mm × 180 mm baseplate anda special manufactured multipass cell of dimension 100 mm × 100 mm × 30 mm, which will undergo
thermal cycling and vibrational tests.

Fig. 170: Photograph of the elegant breadboard
model of the iodine spectroscopy setup. Laser lightis fibre-coupled to the setup with a triple-passconfiguration of a 30 cm iodine absorption cell.

Fig. 2: Allan Deviation of the beat note between
the elegant breadboard iodine reference and acavity stabilized reference laser. A linear drift of
50 Hz/s, attributed to the reference cavity, wassubtracted from the frequency time record.

IFCS-EFTF6-M1-2

A laser frequency stabilization unit for next-generation spaceatomic clocks
A. Nevsky1, S. Alighanbari1, Q.F. Chen1, I. Ernsting1, S. Vasilyev1, S. Schiller1,
G. Barwood2, P. Gill2, N. Poli3, M. Schioppo3, G.M. Tino3, U. Sterr4
1

Institut für Experimentalphysik, Heinrich-Heine-Universität, Düsseldorf, Germany
2

3

National Physical Laboratory, Teddington, Middlesex, UK

Dipartimento di Fisica e Astronomia e LENS, Universita’ di Firenze, Sesto Fiorentino, Italy
4

Physikalisch-Technische Bundesanstalt, Braunschweig, Germany
E-mail: alexander.nevsky@uni-duesseldorf.de

A range of new applications in fundamental physics, in time and frequency metrology, and in geophysics
will be enabled by ultra-precise atomic clocks in space, in part in conjunction with terrestrial clocks. The“Space Optical Clocks” project aims for operating an optical clock on the ISS toward the end of this decade.
An EU-FP7 funded-consortium [1] is currently developing two transportable lattice clock demonstrators,
based on strontium and ytterbium.
One unit of the modular strontium clock apparatus is a compact and reliable frequency stabilization system(FSS) for absolute frequency stabilization of several laser sources at distinctly different wavelengths, needed
for cooling and manipulation of Sr atoms: 689 nm, 922 nm, 813 nm. The FSS setup is based on three low-tomedium-finesse optical cavities, embedded in the same ULE block housed in a small vacuum chamber.
Waves from the lasers are led to the respective cavities using single-mode fibers and fiber combiners. The
lasers are locked to the cavities using the Pound-Drever-Hall technique. For each laser, a waveguide electrooptic modulator (EOM) performs a double phase modulation generating two sideband triplets. The central
line of one triplet is locked to the cavity. It can be frequency-tuned (here, over 600 MHz) relative to thecarrier, allowing bridging the frequency gap between an ULE
cavity mode and the atomic transition frequency. The whole
optical setup (see picture) is assembled into a compact
aluminum vacuum chamber with size of approx. 40 x 30 x 15
cm3 plus a box containing the waveguide modulators (on top)
and the compact, DDS-based control electronics subunit. Threeexternal cavity diode lasers were simultaneously stabilized to
the FSS, using independent EOMs. A fourth laser, theindependently stabilized 698 nm clock laser, can also be
coupled to the FSS. Its purpose is to measure and correct thedrift of the FSS cavity with respect to the ultra-stable reference
cavity. The linewidth and the absolute frequency stability ofthe stabilized lasers were characterized by means of a femtosecond frequency comb stabilized to a H-maser
and a virtual beat with an ultra-stable Yb clock laser. The most critical laser, the 689 nm laser for cooling on
the 1S0  3P1 intercombination Sr transition, exhibits a linewidth of approximately 100 Hz at 1 s integration
time (0.9 kHz at 70 s) and a drift smaller than 0.5 Hz/s. These values are mostly determined by the propertiesof the reference cavity and the environment, since for simplicity, compactness and weight reduction nomeans have been implemented for reducing the vibration sensitivity of the cavity.
The system has been successfully integrated into the Sr compact lattice optical clock at LENS (Firenze,
Italy), achieving robust and stable operation, with 1.1×104 88Sr atoms in the lattice and clock transition
spectroscopy with 23 Hz linewidth.
1

www.soc2.eu; S. Schiller, et al.,“Towards Neutral-atom Space Optical Clocks (SOC2): Development of high-performancetransportable and breadboard optical clocks and advanced subsystems”, in: Let’s embrace space, Vol. II, Ch. 45, ISBN 97892-79-22207-8, doi:10.2769/31208

IFCS-EFTF6-M1-3

Laser dynamics effects on the systematics
of large size laser gyroscopes
J. Belfi1, A. Beghi2,3, N. Beverini1,4 , B. Bouhadef4,
D. Cuccato2,3, A. Di Virgilio4 and A. Ortolan3
12Dept. of Physics, University of Pisa, Largo Bruno Pontecorvo 3, Pisa, Italy
Dept. of Information Engineering, University of Padova, Via Gradenigo 6/B, Padova, Italy
3
INFN National Laboratories of Legnaro, Viale dell'Università 2, Legnaro, Padova, Italy
4
INFN Section of Pisa, Largo Bruno Pontecorvo 3, Pisa, Italy
Email: belfi@df.unipi.it

Large frame ring laser gyroscopes provide precise measurements of local frame rotations induced byearthquakes, tides, local tilts of the terrestrial crust and even by the wobbling of the axis of the planet521.
A ground based experiment aimed at measuring the Lense-Thirring effect with an array of laser
gyroscopes has been recently proposed522. The project foresees the construction of a tri-axial gyroscope
for the measurement of the Earth's rotation vector with a precision better than 10 -9. This goal requires astrict control of all the systematics connected to the geometrical scale factor and to the nonlinear
dynamics of the laser. The complete identification of the laser parameters is then required for theabsolute calibration of such detectors.
We present the results of comprehensive experimental tests of the Lamb's semiclassical theory of ringlasers obtained by operating the “G-Pisa” gyroscope with the laser plane oriented almost perpendicularly
to the local North direction. In this configuration, the Earth's rotation contribution to the Sagnac
frequency is less sensitive to the orientation error, and a more precise estimate of the systematics comingfrom the laser dynamics can be achieved. Cavity losses and the corresponding dissipative Lambparameters are monitored by observing the single beams intensity modulation at the Sagnac frequency
while the gain parameters are identified by a dedicated spectroscopic analysis of the plasma dispersion
function. The adopted methods and the improvements of the ultimate performances of the G-Pisa
apparatus, obtained with the application of a Kalman filter algorithm, will be detailed.

521

K. U. Schreiber et al., “How to Detect the Chandler and the Annual Wobble of the Earth with a Large Ring Laser
Gyroscope”, Phys. Rev. Lett. 107, 173904 (2011).
522(2011).

F. Bosi , et al., “Measuring Gravito-magnetic Effects by Multi Ring-Laser Gyroscope”, Phys. Rev. D 84, 122002,

IFCS-EFTF6-M1-4

Gar-Wing Truong1, James Anstie1,2, Thomas Stace3, Andre Luiten1,2
1
School of Physics, The University of Western Australia, Perth, Western Australia, Australia, 2School of Chemistry andPhysics, and IPAS, The University of Adelaide, Adelaide, South Australia, Australia, 3School of Physics, The University of
Queensland, Brisbane, Queensland, Australia

Determination of the Boltzmann Constant using Laser Absorption
Spectroscopy
G.-W. Truong1, J.D. Anstie1,2, T.M. Stace3, and A.N. Luiten1,2.
School of Physics, University of WA, Nedlands, WA Australia
2
School of Chemistry and Physics and Institute of Photonics & Advanced Sensing (IPAS), University of
Adelaide, Adelaide SA, Australia.
3
School of Physics, University of Queensland, St Lucia, QLD, Australia
1

Email: andre.luiten@adelaide.edu.au
The current CODATA value and its associated uncertainty for the Boltzmann constant, kB, isprimarily derived from a single acoustic measurement performed in 1988[1,2]. Since a call in 2005,
there have been renewed efforts towards a redetermination of kB in preparation for the redefinition of thekelvin[3]. Here, the unit of temperature is no longer tied to a particular state of matter, but instead, to an
ensemble of fixed fundamental constants.
In this talk, we will present recent progress towards a redetermination of kB using high-precision andhigh-accuracy Doppler-broadened spectroscopy of cesium atoms in a thermal vapour cell. By extracting
the width of the Gaussian component of an isolated hyperfine absorption feature one can determine thetranslational thermal energy, kBT, of the atomic vapour. By combining this with an independentmeasurement of temperature T, it is possible to determine the Boltzmann constant[4]. We will present a
Boltzmann constant determination with an 8 ppm statistical uncertainty and discuss sources ofsystematic error.
Spectrometer: The probe laser at 894nm was offset-frequency locked to a stable master laser,
providing a tunable, but stabilized optical frequency to probe the D1 transition. The spectrometer utilises
a single-pass dual-beam topology, with one path detected immediately while the other is directed
through a well-shielded, temperature-controlled cesium cell. We have shown that our spectrometer iscapable of shot-noise limited precision[5].
Systematic Errors: Currently, the performance of our thermal enclosure is the principal limitation toachieving ppm-level accuracy. We will discuss the use of an advanced thermostat which can reduce
temperature gradients to below 15μK – sufficient for a ppm-level retrieval of kB. Whilst the compact,
single-pass topology possible with the highly absorbing alkali metals is a distinct advantage, one mustalso be wary that the atomic population can easily be significantly perturbed away from thermal
equilibrium by the probe source. We have observed and quantified an anomalous power broadening anda spatial beam profile distortion that can be attributed to optical pumping in the 3-level Λ system. Bothof these can disturb the accuracy of the measurements.
[1] Moldover, M. R., et al. "Measurement of the universal gas constant R using a spherical acoustic
resonator." Physical review letters 60.4 (1988): 249-252.
[2] Mohr, Peter J., Barry N. Taylor, and David B. Newell. "CODATA recommended values of thefundamental physical constants: 2006." Reviews of Modern Physics 80.2 (2008): 633.
[3] Fellmuth, Bernd, Ch Gaiser, and Joachim Fischer. "Determination of the Boltzmann constant—status
and prospects." Measurement Science and Technology 17.10 (2006): R145.
[4] Bordé, Christian J. "Base units of the SI, fundamental constants and modern quantum physics."

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences363.1834 (2005): 2177-2201.
[5] Truong, Gar-Wing, et al. "Absolute absorption line-shape measurements at the shot-noise limit."
Physical Review A 86.3 (2012): 030501.

IFCS-EFTF6-M1-5

Hollow-Core Fibre Frequency Standards
1

C. Perrella1,2, J. Anstie1,2, P. Light1,2, A. Lurie1, T. Stace3, F. Benabid4 and A.N. Luiten1,2.
School of Chemistry and Physics and Institute of Photonics & Advanced Sensing (IPAS), University of
Adelaide, Adelaide SA, Australia.
2
School of Physics, University of WA, Nedlands, WA Australia
3
School of Physics, University of Queensland, St Lucia, QLD, Australia
4
GPPMM Group, Xlim Research Institute, CNRS, Universite de Limoges, France
Email: andre.luiten@adelaide.edu.au

A continuing challenge for the broader applicability of high precision frequency standards is thelarge size and fragility of the best examples. This talk presents our research aimed at developing new
platforms for precision measurement based on compact and robust gas-filled hollow-core photonic
crystal fibre (HC-PCF). We will address two particular examples: (i) iodine-filled fibre for delivering aflexible visible light standard suitable for length metrology; (ii) rubidium-filled fibre for a compact
frequency standard based on a narrow two-photon transition.
(i) Iodine523: We have loaded a 50cm long hollow-core (~25µm core diameter) photonic-crystal
fibre with ~5Pa of iodine vapour. By probing with counter-propagating and frequency-shifted 532nm
beams, we see strong and clean Doppler-free resonances with a low-power linewidth of around 6MHz.
This linewidth is dominantly set by transit-time effects across the fibre core. We use FM spectroscopy tolock the laser to one of these spectral lines and have achieved a fractional frequency stability of 2.3 x 1012/√τ where τ is the integration time of the measurement. This stability is consistent with photon shotnoise on the detected signal. We predict that with some improvements to the modulation scheme,
together with lowering of the iodine pressure, it should be possible to improve this stability by a factorof 10.
(ii) Rubidium524: We have loaded a high density of Rb into 15cm of hollow-core optical fibre with a
35µm core diameter. We excite the two-photon resonance (5S to 5D) in Rubidium using two counterpropagating lasers at 780nm and 776nm. This dual colour excitation gives a much stronger transition
than would be the case from a pure 778nm excitation. The high intensity conditions, together with thelong length of the fibre, can result in substantial absorption of IR light (>80%). The observed twophoton linewidth is around 10MHz arising from three effects: transit time (5.6MHz), residual magnetic
fields in the unshielded fibre (2.6MHz) and a residual Doppler effect (3.1MHz) arising from excitationby two different wavelengths. Frequency stabilization of the sum frequency of the two lasers is possibleusing modulation-transfer spectroscopy variant : we observe amplitude modulation on one colour
transferred from frequency modulation on the other. The measured fractional frequency stability of thesum frequency was 9.8 x 10-12 at 1.3s integration time. This performance is limited by varying lightshifts driven by alignment fluctuations. Were these to be suppressed the shot-noise floor corresponds toa level of 10-13 at 1s.

523

Lurie et al, OPTICS LETTERS 36, 4776, (2011).; Lurie et al, OPTICS EXPRESS 20, 11906 (2012).

524

C. Perrella et al. PHYSICAL REVIEW A 87, 013818 (2013); C. Perrella et al, Optics Letters, (2013), submitted

IFCS-EFTF6-M1-6

Towards a new clock laser system using a ceramic cavity andlaser linewidth transfer technique
Kazumoto Hosaka1, Hajime Inaba1, Daisuke Akamatsu1, Masami Yasuda1,
Jun Sugawara2, Atsushi Onae1, and Feng-Lei Hong1
1
National Metrology Institute of Japan (NMIJ), AIST, Tsukuba, 305-8563, Japan
2
Ceramics Division, Krosaki Harima Corporation, Kitakyushu City, 806-8586, Japan
Email: kazu.hosaka@aist.go.jp
Theoretical study shows that the frequency stabilities of ultra-stable lasers at a short averaging time areclose to being limited by mechanical thermal fluctuations of the optical cavities525. A long spacer for thecavity should help to reduce the thermal noise relatively. However, a long cavity could be sensitive tothe vibration. To surmount the problems, there is a need for a new material with high specific rigidity
and very low thermal expansion at room temperature. We have applied an ultra low thermal expansion
ceramic based on poly-crystalline cordierite ceramics (‘NEXCERA’ Krosaki Harima2), which has aYoung's modulus of ~ 130 GPa and a Poisson's ratio of ~ 0.30, to an optical cavity spacer. To evaluate
the thermal expansion coefficient of the ceramic, we produced an optical cavity consisting of two ULE
mirrors in optical contact with a ceramic spacer. The length and diameter of the ceramic spacer were 75
and 25.4 mm, respectively. A Nd:YAG laser operated at 1064 nm was stabilised to the ceramic cavity
and the resonant frequency of the cavity was measured by a fibre-based frequency comb system 3,4. We
found that the ceramic cavity had a zero cross temperature at 16.4 (1) °C where the thermal expansion
coefficient crosses zero5. A finite element based
analysis has been employed to calculate the ceramic
cavity deformation when loaded. The response to thevertical acceleration is estimated from computations of
the axial displacements at the centre of the mirror
surface. A reduction in the response of the ceramic
cavity to the vertical acceleration by a factor of 2
comparing with an ULE cavity has been shown (Fig.
1.). By combining the ceramic cavity with laser
linewidth transfer technique using our high-speed
controllable fibre-based frequency comb3,4, clock lasers
for Yb and Sr optical lattice clocks will be linewidthnarrowed and stabilised.
This research is supported by the MEXT/JSPS through its
FIRST Program and Grants-in-Aid for Scientific Research
Program (KAKENHI Grant Number: 22540415).

Fig. 171: A design of a long cavity and acalculated result of cavity length change
under vertical acceleration as a function of
the support position.

1

K. Numata, et. al., Phys. Rev. Lett., 93, (2004) 250602.

2

J. Sugawara, et. al., Proceedings of ASPE 2010 Annual Meeting, 50, (2010) 405.

3

Y. Nakajima, et. al., Opt. Express, 18(2), (2010) 1667.

4

K. Iwakuni, et. al., Opt. Express, 20, (2012) 13769.

5

K Hosaka, et. al., Jpn. J. Appl. Phys., 52, (2013) 032402.

Modeling and Frequency Synthesis
CLUB HThursday, July 25 2013, 02:00 pm - 03:30 pm
Chair:David HoweNISTIFCS-EFTF2-M2-1

Physical model of phase noise in feedback oscillator
Xianhe Huang
School of Automation Engineering, University of Electronic Science & Technology of China, Chengdu,
Chinaxianhehuang@uestc.edu.cn
Background: The phase noise of feedback oscillator is a key factor which limits the performance of electronicsystem.

Classical Leeson Model Analysis: When applying this model to design a feedback oscillator, one
should know what key points should be paid more attention to? What drawbacks of this model also
should be noted1-4. In this paper, determinants between loaded quality factor QL and equivalentparameters of a resonator and that of a oscillation circuit are tried to be revealed, influencing factors ofnoise factor F and corner frequency f c are analyzed, and improvement measures are discussed as well.
Design examples and analysis:
Low phase noise quartz crystal BAW oscillator with AT-cut and SC-cut resonator5.
Low phase noise oscillator with SAW resonator6.
Low phase noise bulk wave oscillator with LiTaO3 resonator7.
LC / RC feedback oscillator.
Conclusion:
The loaded quality factor QL is a dynamic parameter.
The noise factor F is also a dynamic parameter.
Discussion:
Further studies about methods for improving the phase noise performance of the feedback oscillator.
References:
1. John R. Vig “ Quartz Crystal Resonators and Oscillators for Frequency Control and Timing Applications - A Tutorial ” http://www.ieee-uffc.org [Online]
2. Jeremy Everard “Low Phase Noise Signal Generation, Models and Theory, Oscillators and Their Key Elements, Fractional Regenerative Frequency
Division, Teaching”,2012 IEEE International Frequency Control Symposium
3. Michael Driscoll “Modeling Phase Noise in Multifunction Subassemblies” Frequency Control and the European Frequency and Time Forum (FCS), 2011
Joint Conference of the IEEE International
4. E. Rubiola and V. Giordano, “On the 1/f frequency noise in ultra-stable quartz oscillators”, IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 54, no.
1, pp. 15-22, Jan. 2007.
5. Huang, Xianhe “The Design and Implementation of a 120-MHz Pierce Low-Phase-Noise Crystal Oscillator”, IEEE Trans. Ultrason. Ferroelectr. Freq.
Control, vol. 58, no. 7, pp. 1302-1306, 2011
6. Huang, Xianhe “Optimization and Realization of a 315-MHz Low-Phase-Noise Voltage-Controlled SAW Oscillator”, IEEE Trans on Circuits andSystems II-Express Briefs, Vol: 59 no: 1 pp: 16-19, 2012
7. Huang, Xianhe “Design of a Wide-Tuning-Range Lithium Tantalate Low-Phase-Noise Voltage-Controlled Oscillator”, IEEE Trans on Circuits andSystems II-Express Briefs, Vol: 60 no: 3

IFCS-EFTF2-M2-2

Design, Simulation and Test of an Oscillator Suitable for Wafer Level
Evaluation of SAW Resonator Phase NoiseDan Porga, Twinkle Shah, Dennis Thoma, Andrew Sawyer, Mike Driscoll (Consultant)Phonon Corporation, Simsbury, CT, USA
Email: DanP@phonon.com
In a well-designed BAW or SAW oscillator, the primary contributor to near-carrier, flicker-of-frequency
noise should be the resonator itself and not the sustaining stage amplifier. Determination of resonatorshort-term frequency stability (self-noise) at the wafer level is highly desirable from both the perspectiveof resonator selection prior to packaging and evaluation processing conditions resulting in low noise
resonators. The objective of this work was to design a SAWR oscillator where both the flicker-of-PM
noise contribution of the sustaining stage could be reliably determined. In addition, the oscillator designneeded to be compatible with and tolerant of coaxial probe connections to on-wafer resonator arrays.
It was decided to design the oscillator using a 50 ohm sustaining stage amplifier. To this end, several
candidate amplifiers were evaluated, including inexpensive, tape-and-reel type amplifiers containing
darlington pair configurations with resistive feedback as well as SMP modular amplifiers. A novel
method was used for very simple and accurate determination of amplifier flicker-of-PM white (additive)noise without the SAW resonator installed that consists of oscillator operation using an intentionally low
delay (low Q) LC resonator or band-pass filter. The amplifier operating point (bias, excess gain, etc) is
the same as with the SAWR installed, except the open loop white PM and 1/f PM noise is intentionallyenhanced to quite high and easily measurable levels. We observed a reasonably large spread in 1/f PM
noise for different model tape-and-reel amplifiers purchased from the same vendor. The same method
was used in a discrete component sustaining stage, and in that case, resonator loading was bothmeasured and successfully simulated via determination of the 1/2πτ corner frequency in the phase noise.
The wafer probe oscillator was first evaluated using packaged resonators where the sustaining stage
contribution towards oscillator near-carrier noise was 6-10dB below the best resonators. The oscillator
was then installed in a wafer probe set-up, where extraordinary measures needed to be taken to reduce
the effects of acoustic noise, electrical interference and vibration. The current status is that the results
obtained for evaluation of packed and on-wafer devices are quite comparable.

IFCS-EFTF2-M2-3

Synthesis of Ultra-Stable Radio Frequency Signals From
Independent Microwave Frequency Oscillators
John G. Hartnett1,2, Stephen R. Parker1, Eugene N. Ivanov1, Nitin R. Nand1
1

2

School of Physics, The University of Western Australia, Crawley, Australia
Institute of Photonics and Advanced Sensing, School of Chemistry and Physics, University of Adelaide,
Adelaide, Australia
Email: stephen.parker@uwa.edu.au

Fractional Frequency Stability

We present the design, implementation and evaluation of 10 MHz, 100 MHz and 1 GHz signals
synthesized from two nominally identical 11.2 GHz Cryogenic Sapphire Oscillators (CSO). The
fractional frequency stabilities of the CSOs for integration times below 5 seconds are comparable to thestate-of-the-art performance of X-band signals generated by optical-comb division526, while stability for
integration times from 5 to 4000 seconds remains without peer. This translates in to low phase noise,high frequency stability performance of the-14
10
generated RF signals, with applications in(1) 10 MHz synth
1
millimeter wave Very Long Baseline(2) 100 MHz synth(3) 1 GHz synth
Interferometry.
(4) 11.2 GHz cryoCSO
Previous work reported on the synthesis of a
10 MHz and 100 MHz signal from a single
2
-15

10
CSO527, we have now synthesized these signals
independently from separate CSOs and directly
compare them. We also generate a 1 GHz
signal by phase locking a voltage controlled
oscillator to a 1 GHz output derived from a-16
CSO. Fractional frequency stabilities at 1
10
0
1
2
3
4
10
10
10
10
10
second integration time are 1×10-14, 2×10-15-15IntegrationTime(s)and 1.5×10 respectively for the 10 MHz, 100
MHz and 1 GHz signals (Fig. 1). Single Fig. 172: Fractional frequency stability of 10 MHz
sideband phase noise at 1 Hz offset is -134 (curve 1), 100 MHz (curve 2), 1 GHz (curve 3)
dBc/Hz for the 10 MHz signal (≈12 dB lower signals and an 11.2 GHz CSO (curve 4).
than the best commercial 10 MHz quartz
oscillator), -130 dBc/Hz for the 100 MHz signal (>25 dB lower than the best commercial 100 MHz
quartz oscillator) and -112 dBc/Hz for the 1 GHz signals. Phase noise performance is limited by thefrequency dividers and is surpassed only by signals synthesized using regenerative dividers 528.
Possibilities for improvement will be discussed.
526

T.M. Fortier, M.S. Kirchner, F. Quinlan, J. Taylor, J.C. Bergquist, T.Rosenband, N. Lemke, A. Ludlow, Y. Jiang, C.W.
Oates, and S.A. Diddams, “Generation of ultrastable microwaves via optical frequency division,” Nature Photonics, vol. 5,
pp. 425-429, 2011.
527
N.R. Nand, J.G. Hartnett, E.N. Ivanov, G. Santarelli, “Ultra-stable very low-phase-noise signal source for Very Long
Baseline Interferometry using a cryocooled sapphire oscillator,” IEEE Trans on Micro. Theory & Tech., vol. 59, no. 11, pp.
2978 – 2986, 2011.
528

A. Hati, C.W. Nelson, C. Barnes, D. Lirette, J.A. Desalvo, T. Fortier, F. Quinlan, A. Ludlow, T. Rosenband, S.A.
Diddams, D.A. Howe, "Ultra-low-noise regenerative frequency divider for high-spectral-purity RF signal generation,"
Frequency Control Symposium (FCS), 2012 IEEE International , vol., no., pp.1-4, 21-24 May 2012.

IFCS-EFTF2-M2-4

The sampling theorem in Π and Λ digital frequency dividers
Claudio E. Calosso1 and Enrico Rubiola2
12

Division of Optics, INRIM, Torino, Italy
Department of Time and Frequency, CNRS FEMTO-ST Institute, Besancon, FranceHome page http://rubiola.org
Email: c.calosso@inrim.it and rubiola@femto-st.fr

The noise-free frequency divider can be assimilated to an ideal gearbox that divides the input frequency by d,transferring the total jitter δt from the input to the output. Accordingly, the phase-noise spectral density isruled by [Sφ(f)]out = [Sφ(f)]in/d2. So, a modulo-10 divider reduces the input phase noise by 20 dB.
In the classical (Π) digital divider (a chain of flipflops), the output white noise is [Sφ(f)]out = [Sφ(f)]in/d. The
denominator is d instead of d2. So, a modulo-10 divider
reduces the input noise by 10 dB instead of 20 dB. This
unfortunate outcome is due to the sampling theorem
applied to phase noise. In fact, the phase noise is sampled
at the rising and falling edges of the square wave, whichmeans at a sampling frequency 2νin at the input, and 2νoutat the output. Owing to the Parseval theorem, the time
fluctuation is <(δt)2> = Sδt(f) B, where B is the noise
bandwidth, i.e., the Nyquist frequency. Down-samplingby a factor of d at the output, the spectrum of the time
fluctuation scales up by a factor of d.
Our de-aliased (Λ) divider uses shift registers and a
resistor network to generate a triangle-like waveform at Fig. 173: Phase noise in noise-free modulo-10
frequency νout = νin/d, sampled at the full speed 2νin. Π and Λ dividers.
Having removed the down-sampling phenomenon, theoutput noise is [Sφ(f)]out = [Sφ(f)]in/d2, as in the ideal
divider. The phase noise is equivalent to that of a noise-free DDS529. By contrast, the complexity of a Λdivider is a mere factor of 2–3 higher than that of a Π divider, and suitable to simple/cheap gate arrays.
The schemes are called Π divider (traditional) and Λ divider (de-aliased). The names follow the output
waveform, as in the case of the weight function of the Π and Λ counters530.
In a real divider, the input sampling, inherently, introduces noise. Additionally, the output stage can be alimiting factor because its phase noise adds up after scaling down the input noise. Flicker noise does not
behave as described because the electrical power in higher-frequency aliases is low. However, we have goodreasons believe that the flicker noise can be lower in Λ divider, as compared to the Π divider. This will
discussed only after further experiments.
The article provides theory and experimental verification of the phase-noise aliasing, and demonstrates thevirtues of the Λ divider.

529
530

C. E. Calosso, Y. Gruson, E. Rubiola, “Phase noise in DDS,” Proc. 2012 IFCS p. 777–782.

E. Rubiola, “On the measurement of frequency and of its sample variance with high-resolution counters,” Rev. Sci.
Instrum. 76(5) 054703, May 2005.

IFCS-EFTF2-M2-5

Trim Effect Compensation Using an Artificial Neural Network
John Esterline
Engineering, Greenray Industries, Mechanicsburg, PA
Email: jesterline@greenrayindustries.com
Trim effect is a skewing of the frequency versus temperature performance of a crystal oscillator as thefrequency is pulled (trimmed) away from the oscillator’s nominal frequency. As TCXO (Temperature
Compensated Crystal Oscillator) frequency versus temperature stabilities have improved to ppb (part perbillion) levels trim effect has become more of a concern. Even though unwanted, the degradation of
performance from trim effect is something generally accepted as a characteristic of TCXOs. This paper
focuses on a method of compensating crystal oscillator trim effect. Through the use of an artificial
neural network, trim effect compensation of AT cut crystal oscillators can be achieved with better than+/-15ppb stability over the industrial temperature range (-40 to +85 °C). This is more than a 10 foldimprovement over the inherent trim effect found using state of the art polynomial function generator
compensation, see Figure 1 below. The theory of this compensation method with be discussed, and data
showing the results of trim effect compensation on actual oscillators will be presented.

Figure 1: Comparison of Trim Effectuncompensated (left) versus compensated (right).

Novel Sensing Materials and Devices
CLUB D
Thursday, July 25 2013, 02:00 pm - 03:30 pm
Chair:

Fabien Josse
Marquette University

IFCS-EFTF4-M3-1

Piezoelectric Acceleration Sensors Based on LGX and ReCOB
Crystals for Application above 645 DegC
Yanqing Zheng1, Xiaoniu Tu1, Jianjun Chen1, Pan Gao1, Erwei Shi1
1

Shanghai Institute of Ceramics, Chinese Academy of Sciences, Jiading, Shanghai/P. R. China
Email: zyq@mail.sic.ac.cn

Piezoelectric acceleration sensors that could stand environment temperature above 645ºC (1200ºF) areof great important to the field of vibration monitoring of aviation and aerospace engine. The traditionalpiezoelectric materials used in this area include lithium niobate crystal, bismuth layer structure systempiezoelectric ceramics531. But the issue of the lower electric resistivity limits their application oftemperature higher than 645 ºC. GaPO4 crystal which is grown by hydrothermal method could be used
up to 900 ºC. However, the difficulty in crystal growth of GaPO4 crystal makes it very expensive andlimits its application.
ReCOB (Re= La, Y, Sm, Nd, Lu) crystals and LGX crystals including LGT, LGN and LGS are
piezoelectric crystals with high melting points above 1400ºC and without phase transition from room
temperature to their melting points. All of these crystals can be grown by common Czochralski method
up to 4 inches. They are all good candidates for high temperature application.
LGT, LGS, YCOB and SmCOB were grown withefforts to study the factors affecting the electric
resistivity of each crystal and increase their electric
resistivity under high temperature in our laboratory inrecent years. LGS and YCOB with diameter of 4
inches, LGT of 3 inches and SmCOB of 2 inches
were successfully grown and the basic physicalproperties and crystal quality were characterized. The
rocking curve of high-resolution X-ray diffraction(HRXRD) of these crystals shown that they were ofhigh quality. Piezoelectric acceleration sensors used
the X-cut rings of 10 mm diameter based on these Fig. 174: The sensitivity vs temperature curve of thecrystals were fabricated and tested. It was shown that piezoelectric acceleration sensors based on LGT
crystal grown in SICCAS .
our as-grown LGT crystal could be used up to 645 ºC
with very steady sensitivity. YCOB and SmCOB
crystals could be used to higher temperature up to 900 ºC after overcoming the issue of pyroelectriceffect.

531

S.J. Zhang, X. N. Jiang, M. Lapsley, et al, “Piezoelectric acelerometers for utrahigh temperature aplication”, Appl. Phys.
Lett., vol. 96(1), p.013506, 2010.

IFCS-EFTF4-M3-2

Thin quartz layer transferred on silicon for SAW applications
S. Grousset1, E. Augendre1, T. Signamarcheix1, T. Baron2, E. Courjon2, S. Ballandras2
1

CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 GRENOBLE Cedex 9, France.
2
FEMTO-ST, UMR 6174 CNRS-UFC-ENSMM-UTBM, Besançon, France.
Email: sebastien.grousset@cea.fr

Motivation
The transfer of piezoelectric material is of a great interest for the direct integration of Surface Acoustic
Wave (SAW) devices on silicon wafers. This approach offers a lot of opportunities for the developmentof smart devices dedicated to sensing or integrated frequency sources. However, the bonding/thinning
process must allow preserving SAW properties, comparable with devices built on single-crystal wafers.
Achievement
We present improved results on the development of single-crystal quartz layer transferred onto siliconthrough direct wafer bonding and thinning process. One-port SAW resonators have been built using a
stepper-based industrial process. To overcome the Temperature Coefficient of Expansion (TCE)
difference of dissimilar materials like quartz (13.2 ppm/°C) and silicon (2.3 ppm/°C), a low temperature
direct wafer bonding process has been implemented. This process is performed at atmospheric pressure
with low temperature annealing (<200°C). InfraRed (IR) imaging shows excellent bonding quality withno defects.
Results
Thin AT-cut quartz layers of about 100 µm were obtained after grinding and polishing process. While
the thinning process of quartz is likely to be known for increasing crystal disorder and to induce some
defects in the transferred layer532, our quartz thin films are achieved without any damaged layer and witha crystal quality equivalent to bulk material. Aluminum electrodes were deposited on quartz to achieve
SAW resonators. Figure 1 shows the resonators obtained on the hybrid quartz/silicon wafer. Inter Digital
Transducers (IDT) were designed to generate Rayleigh waves at 430 MHz. The electrical response of asingle-port SAW resonator is shown in figure 2 where the fundamental resonance exhibits a Q-factor of
about 12500.
The developed process was applied to different quartz crystal orientations to satisfy a large variety of
applications.

Fig. 1: SAW resonators on a 100mm hybrid wafer.
532

Fig. 2: Admittance of a SAW resonator.

B. Imbert et al., “Thin film quartz layer reported on silicon,” in 2011 Joint Conference of the IEEE International
Frequency Control and the European Frequency and Time Forum (FCS) Proceedings, 2011, pp. 1–4.

IFCS-EFTF4-M3-3

Acoustic properties of carbon nanotubes as high acoustic impedance electrode in BAW resonators

E. Iborra, L. García-Gancedo, S. Esconjáuregui, J. Sangrador, M. Clement, M. de Miguel-Ramos, J.
Olivares, J. Capilla, A. J. Flewitt, W. I. Milne
GMME-CEMDATIC, ETSIT, Universidad Politécnica de Madrid, Spain
Electrical Engineering Division, Department of Engineering, University of Cambridge, UK
E-mail: eiborra@etsit.upm.es
Bulk acoustic wave (BAW) resonators can be used as gravimetric sensors by tracking the shift in theresonant frequency that takes place when the mass of the devices changes due to the adsorption of
biological or chemical agents. To promote the adsorption of a specific agent the uppermost layer of thedevice has to be adequately functionalized. In addition, to increase the quality factor of the resonator, it
is advisable to use a top electrode with an acoustic impedance as high as possible, which provides alarger confinement of the mechanical energy into the piezoelectric. At the same time, the weight of the
top electrode should be kept as low as possible to avoid lowering the electromechanical coupling factor.
Therefore, the ideal top electrode would be a highly conducting material, exhibiting low mass density
and high acoustic velocity, which would double as an electrode and as a sensing layer. Because of theirmorphology, carbon nanotubes (CNT) have densities below 1 g/cm3. They also exhibit low resistivity
and very high elastic constants, which lead to a high propagation velocity. These features, together withthe possibility of being functionalized and their exceptionally high surface to volume ratio, make CNT
layers very good candidates as top electrode in gravimetric sensors based on BAW resonators. For
designing purposes, a deep knowledge of the material properties is required. In this communication we
present a study of the acoustic properties (sound velocity and acoustic impedance) of CNT layers bymeans of the characterization of BAW resonators using a CNT layer as top electrode.
BAW resonators consisting of a Mo/AlN/CNT piezoelectric sandwich were built on acoustic mirrors
composed of Mo and SiO2 alternating layers deposited on a silicon substrate. The CNT film used as top
electrode was grown on a Ti layer by the pyrolithic decomposition of C2H2 diluted in NH3 using Fe
nanoparticles as catalytic agent. The frequency response of the resonators was assessed as a function of
the thickness of the CNT electrodes, which varied from 0.5 µm to 10 µm. Apart from the resonant
frequency corresponding to the longitudinal mode in the AlN, a λ/2-resonance is also excited into the
CNT layer, whose frequency is related to the thickness and the sound velocity of the film. To derive thedensity, the sound velocity and the acoustic losses of the CNT layers, the frequency response of theresonators was fitted using the Mason’s model; as inputs we used the values of the densities, the acoustic
velocities and the losses of all the layers involved in the device (Mo, SiO2, Ti and AlN) that had been
accurately determined in previous works, as well as their thicknesses assessed by profilometry. We haveobtained values of the mass density varying from 0.1 g/cm3 to 0.5 g/cm3 and sound velocities around
18000 m/s, which lead to acoustic impedances ranging from 1.8·106 kg·m-2·s-1 to 9·106 kg·m-2·s-1. Whengrown under specific conditions, CNT layers possess higher acoustic impedance and lower density thanthe metals commonly used as electrodes in BAW devices (Mo, Au, Cr, Ti, Zr, Ag, Pt, Al), which makes
them suitable as low mass electrodes with high acoustic impedance and low series resistance. Raman
spectroscopy, XPS, AFM and SEM characterization has been performed to determine the structure of
the CNT layer.

IFCS-EFTF4-M3-4

Properties of Piezoelectric Single Crystals Ca3TaGa3Si2O14 at HighTemperature and High-Vacuum Conditions
Hongfei Zu1, Huiyan Wu1, Yinzhong Wang1, Qing-Ming Wang1
Shujun Zhang2, T.R. Shrout2
1
Department of Mechanical Engineering & Materials Science, University of Pittsburgh,
Pittsburgh, PA, USA, Email: qiw4@pitt.edu
2Materials Research Institute, The Pennsylvania State University, University Park, PA

High temperature sensors which could be appliedsafely and stably under harsh environments are ofmajor importance to the aerospace and energy
industries1. Recently, a kind of fully orderedlangasite family crystals Ca3TaGa3Si2O14 (CTGS)
have attracted considerable attention for hightemperature applications2. In this paper,
Piezoelectric single crystals Ca3TaGa3- Si2O14(CTGS) were grown by the Czochralski pulling
method along ˂100> direction and cut into lateralmode. The dielectric, elastic and piezoelectric
properties of them were investigated as functionsof temperature (up to 1073.15K) and pressure (upto E-7 torr). It was found that all the crystals Fig. 175: Resonant frequency as a function of
exhibited pressure stability properties (up to E-7 temperature for CTGS lateral mode crystal attorr) and temperature dependent characteristics different pressures.
(up to 1073.15K). Fig. 1 presents the resonant
frequency as a function of temperature at differentpressures, exhibiting linear temperature/frequency
characteristics over a wide temperature range.
According to our calculation, the dielectric⁄ , elastic coefficientpermittivity
andpiezoelectric coefficientwere 17.66 (3.75%),
8.83~9.29 (pm2/N) and 3.77 (2.11%) (pC/N),
respectively. Fig. 2 gives the elastic constant ( s11E ,E) as a function of temperature at differents22
pressures. The good properties make CTGS
promising candidates for sensing applications at
high-temperature and high-vacuum conditions.

Fig. 2: Elastic constant variation as a functionof temperature for CTGS lateral mode crystal at
Fapeng Yu, Shujun Zhang, Xian Zhao, Duorong Yuan,
Lifeng Qin, Qing-ming Wang and Thomas R. Shrout, different pressures.
1“Investigation of Ca3TaGa3Si2O14 piezoelectric crystals for high temperature sensors,” Journal of applied physics 109,
114103, 2011.
2

S. J. Zhang, Y. Q. Zheng, H. K. Kong. J. Xin, E. Frantz, and T. R. Shrout, “Characterization of high temperature
piezoelectric crystals with an ordered langaste structure,” J. Appl. Phys. 105, 114107, 2009.

IFCS-EFTF4-M3-5

1High Overtone Bulk Acoustic resonators for high temperature sensing
applications

Emilie Courjon, 2Marc Loschonsky, 1Bruno François, 1Gilles Martin, 1William Daniau, 2Jean-Michel
Friedt, 2Brahim Belgacem, 1Thomas Baron, 3Leonhard Reindl, 4Sylvain Ballandras
FEMTO-ST, UMR 6174 CNRS-UFC-ENSMM-UTBM, Besançon France
SENSeOR, SAS TEMIS Innovation, Besançon – Mougins, France
IMTEK, Freiburg, Germany
frec|n|sys, Besançon France

The development of elastic wave sensors capable to be remotely interrogated without on-board energy
has yield new markets rise. The corresponding users challenge these sensor for several extreme
applications such as operation at temperature above 500°C. Although the use of Langasite was the mostpromising approach, Aluminum Nitride (AlN) based structures were also considered as a potential
solution. It was demonstrated that high overtone bulk acoustic resonators (HBARs) can be applied for
wireless sensing as an alternative to SAW resonators. As AlN is well-suited for such devices and exhibita melting point in excess of 2000°C, the idea to exploit AlN-based HBAR for high temperature
operation was considered in the present work.
AlN-based HBARs have been manufactured in a Sigma-Trikon sputtering machine, depositing 1µm
thick layers onto a (111) Ti/Pt backside electrode deposited atop 530µm thick Sapphire and 400µm thick
Silicon substrates. The classical figure of HBAR response was observed, with a frequency separation of
about 8 to 9 MHz depending on the substrate and a maximum resonance of the layer alone near 2 GHz.
The resonances between 400 and 500 MHz (close to the 434 MHz centered ISM band, Fig.1) have been
focused for assessing the operation of the devices at temperature larger than 500°C.
These devices have been submitted to temperature cycles up to 600°C for 48 hours in an oven developed
at IMTEK for calibrating acoustic devices, and their electrical response were monitored at various
frequencies during the experiment. The observation of the device showed minimal deweting effects inform of single droplets atop the surface. The material lattice was found stable enough to withstand thetemperature induced tensions as the thermal grooving and the resulting forming of droplets leaving
micro cavities in the metallization layer is limited. The experiments then were extended successfully up
to 800°C. The use of these HBAR for wireless applications will be tested in the near future.

Fig. 2: Electrical response of a AlN/Sapphire HBAR before and after exposition to 600°C
for 48 hours

IFCS-EFTF4-M3-6

Langatate Temperature-Compensated BAW Orientations
Identified Using High-Temperature Constants
Peter Davulis, Mauricio Pereira da Cunha
Electrical and Computer Engineering Dept. University of Maine, Orono, ME, USA
Email: mdacunha@maine.edu
There is a growing demand for high-temperature (>200°C) sensors and frequency control devices.
Langatate (LGT) crystal is a prime candidate substrate for surface acoustic wave (SAW) and bulk
acoustic wave (BAW) devices to address high-temperature sensing applications due to demonstrated
long-term harsh-environment operation and recently published acoustic wave constants up to 900°C.
While prior work by the authors on LGT has focused on high-temperature SAW performance, LGT
BAW devices capable of operating in harsh-environments enable additional applications such as
deposition rate monitoring, gas, chemical, and physical sensors, and high-temperature timing devices.
In this work, LGT BAW orientations are investigated up to 900°C for temperature-compensatedorientations targeting harsh-environment applications. The study utilizes recently published LGT elastic,
piezoelectric, and dielectric constants extracted by the authors using resonant ultrasound spectroscopy(RUS) up to 900°C based on the resonances of bulk crystal samples. The constants were independently
verified with high-temperature SAW measurements. Temperature-compensated LGT BAW orientations
are investigated and discussed based on the analysis of the temperature coefficient of frequency (TCF),
the turnover temperature (TCF=0) and the piezoelectric coupling for both thickness-field and lateralfield excitation of the three bulk wave modes.
A range of LGT BAW orientations are identified with turnover temperatures up to 550°C, which enable
their use in high-temperature harsh-environment applications. Temperature-compensated orientations
are uncovered for both the slow-shear (c) and fast-shear (b) modes and for both thickness-field and/or
lateral-field coupling at high temperatures. The c-mode turnover temperatures are plotted in Fig. 1
against the angles φ and θ for theorientation Euler angles (φ, θ, 90°), BAW
cut(YXwl) φ, θ.
Theidentified
temperature-compensated orientations arecompared in the paper with plots of thepiezoelectric coupling to determine selectorientation regions with TCF=0 at 550°C
and coupling up to 0.1 for thickness
excitation or up to 0.14 for lateral
excitation.
Additionally,b-modeorientations were identified with turnover
temperature up to 150°C. The data
provided in the paper allows the selectionof temperature-compensated LGT BAW
orientations up to 550°C, considering
different thickness and lateral field
excitations values for a given sensor or Fig. 176: Contour plot of LGT BAW c-mode turnover
temperatures for Euler angles (φ, θ, 90°).
frequency control application.

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