可視赤外線の超伝導検出器の紹介
quasi-particles
hf
Cooper pair

国立天文台
先端技術センター
関本裕太郎

∆
∆

EF

半導体

超伝導

Bandgap

~ eV

~ meV

運用温度

20 ~ 100 K

100 mK ~ 4 K

時間分解能~ msec~ µsecEmpty state
Conduction
Band
Forbidden
Band
Valence
Band

∆
∆

EF

Occupiedstate超伝導Cooper pair-breaking検出器•

SIS : Superconductor - Insulator - Superconductor•

STJ : Superconductive Tunnelling Junction••

MKID : Microwave Kinetic Inductance Detector••

SIS = STJ 準粒子生成によって生じる電流を読み出す。

準粒子生成によって生じるインダクタンスの変化を読み出す。

TES : Transition Edge Sensorは、温度を計測するbolometer

quasi-particles
hf

∆
∆

EF

Cooper pair
超伝導検出器 2014/12/4 Y. Sekimoto

3

SIS mixer
T. Tamura et al. 2014 IEEE AS
ALMA Band 4 (125 – 163 GHz)
ALMA Band 8 (385 – 500 GHz)
ALMA Band 10 (787 – 950 GHz)

4

200nm
Nb-Al-AlOx-Nb

近赤外線超伝導検出器•

Band gapが小さい 2∆ ~ 1 meV••

配線層 = 超伝導線路
•

•

分光が可能

量子効率を高くできる

大面積•多ピクセルは難しい

超伝導検出器 2014/12/4 Y. Sekimoto

5

ARCONS: B. Mazin + 2013 PASP 125, 12

|S21|

0.6

0.4

4
A microlens focuses the light on to the 40×40 μm inductor. The MKIDs in ARCONS absorb light directly
up toabsorption
6 filters forwith A
in theTiN film that comprises the inductor. This TiN has an intrinsic
of calibration.
roughly 70%Observing
at 400Figure 1. Left: The basic operation of an MKID, reprinted from (Day et ais typicallydone
a filterpositionstates N(E) of a atsuperconductor
withwheel
gap . Photons
with energy thath⌫ are a
nm, and 30% at 1 µm. 2024 (44×46) pixel array. Tc is about 800 mK. The
surfaceinductancea highand producing
a numberof excitations calledis
quasiparticles.
(b) To sensitiv
contain afrequency
filter.
planar resonant circuit. In right panels the amplitude (c) and phas
the resonator as a function of frequency is shown. The change in the surfac
25 pH/square. 222×222 µm square. The quasiparticle lifetime inThe
our dewar
TiN
is 50–100µs.andaispushesfilms
theentrance
resonance
to lowerfrequencychanges
amplitude. If thewindow
anitsachromatic
microwave signal, the energy of the absorbed photon can be determined by mexample of frequency
multiplexing
MKIDs showingopti
many rthedomain
light.
All(FDM)
the ofpowered
4 maximum count rate of approximately 2500 cts/pixel/second. which collimatestypic
Edmund Optics VIS-NIR anti-reflection coatin
to lo
tion
perforsurfacebetweenObserving
4000-10000Å)provexup
to <1%
6 filters
calibration.
with
aA
th
meniscus
11 and12 in Table
Prevd
isBK7
typically
donelens
at a(Surface
filter wheel
positionthattions
is uncoated.
thecontaina filter.The light then passes through thatlimit
77
K shieldba✏e, andencountersthThe
dewar thoughentrancea window
is anachromatic
1998
M
4 K radiation
AtAllthethe4 powered
K radiationwhichcollimatesshield.
the light.
optic
with
10
Asahi SuperCold
filter1 isanti-reflection
placed to set coating
the aredM
EdmundOptics VIS-NIR
men
ARCONS’s
sensitivity.
This wassetion<1% perwavelengthsurface between
4000-10000Å) itsel
ex7.3. Sensitivity
sub0.25
vatively
at 1.1lensµm(Surface
in order11toand
reducesky
cou
BK7
meniscus
12
in
Table
et al1
Complete
System(Measured)
The MKIDs in ARCONS absorb light directly in thein subsequent
runs
we
will
attempt to suchex
isbut
uncoated.
The light
thenpassesComplete
System(Model) through the
Figure 2. A photograph of a 2024 pixel UVOIR MKID array
TiN film that comprises the inductor. This TiN has an
isab
ARCONS
Only(Lab
Measurement)
wavelength
coverageout
through
J
band
to
1.3
(with
microlensremovedforclarity)inamicrowave
package.
of th
770.20K shield though a ARCONS
ba✏e,Only
andencounters the(Model)intrinsic absorption of roughly 70% at 4000 Å, and 30%
highis a pupil
imageatchanges
44KKinsuitablefor
4 KThereradiation
shield.
At thetheradiations
FigureLeft:microscope
image of a isportionof bythethe2024
ature electronics
can recoveramplitude
fittinat3.
1 µm.
TheAtotal
system throughput
reducedandphasewithout significant
talk (McHugh
et al. turne
1Lyotcrosscold 2.1mm
diameter
stop,
but
this
ray
pixel MKID
array used200” telescope.
microlenscumulativee↵ectatofthe
allPalomar
the intervening
opticalAmateriAsahi
SuperColdis panelplacedto1. set
the red2012), as shownfilterin the rightof Figureonto
focusesals
theandlight
on to theµm inductor.
VariousM1–M4
features oftobenecessary
because
the
glass
in
the
optic
The
primary
theoreticallimitationonthespectralressurfaces;
the40⇥40
atmosphere,
the telescope
ARCONS’s
wavelength sensitivity. This was easil
set
0.15
olution is from the intrinsic quasiparticle creation statisinterestmirrors
are labeled.
Right:
A
zoomed
in
view
of
the
array
in
the
ative
(the Coudé M3 at Palomar was degraded due toblocks out
enoughof
300toK
thermalblackbtics 1.1
duringthe photon
absorption
event.
The energy
vativelyatµm
in theorder
reducesky
coun
ourleft panel.
> 10 years since realuminization), the collimating lens,fromthe photon
can
endmK
up in twoplaces, thequasipartitime
ation
to
keep
the
100
stage
from
warmingbutinsubsequent
runs
we
will
attempt
toext
cle
systemandthephononsystem.
Thesesystems
inter2500
the Asahi Supercold Filter at 4 K, the 4 optical elements
SuperColdfilterdoes
e↵ectivelyfunction
as
a cp
act,
allowing
energyexchange
between
the
two,
which
re0.10ing
wavelength
coverage out through J band to 1.35
at 4K, the 100 mK glass with ITO filter, and the miduces the statistical fluctuation from Poisson by the Fano
Af
stop
with
a Fpupildiameterof to12
mm.
There
tw
factor, typicallyimage
assumed
be 4
0.2 K
(Fano
1947). Theare
have
There
is
a
at
suitableforpcrolensfillfactorandalignmentwiththeinductors.
A
Figure 3. Left: A microscope image of a portion of the 2024
spectralresolutionofthedetector,
R
=
/
=
E/
E,
Figu
matic
at 4 K
toqdecollimate
theturned
beam
model
of thison a simple
atmocold
2.1doubletsmm
diameter
Lyot
stop,
but
this
pixel MKID
array
used entire
at the system,
Palomar based200” telescope.
A microlens
⌘h⌫
1
is R
can be written as R = 2.355 F , where ⌘ is the effi0.05 platethescale,
butthese
achromatsarephysicspheric
clean
Al reflectivity(normalized
to 86% ofdianfocuses thelightmodel,
on to the40⇥40
µm inductor.
Various features
to be necessary
becausetheintoglassin theciency of conversionof energy
quasiparticles,
typi-opticsnm), manufacturer’s
specs
for glasses,
AR coatinterest at
are670labeled.
Right: A zoomed
in viewof the arrayin thearatedout
tocallyenougheliminate
any
withTypdi0.57 (Kozorezov
et al.potential
2007),Kh⌫ thermalis theissues
photon blackbo
enblocks
of
the
300
swee
ergy,
F
is
the
Fano
factor,andistheenergygap.
Theings, and the Supercold Filter, and measurements of theleft panel.
are athermalcontraction
betweenthefromdi↵erent
glass
energygap
dependsonthe superconducting
transition
ation
to
keep
the
100
mK
stage
warming0.00
withabsorptivity of raw TiN films, is shown as a red solid lineof theinductor,⇡ 1.72kB10000
Tc , andwetemperature(Tc ) 7000
the
final
4
K
optic,
thelightreaches
the
100
m
4000
5000
6000
8000
9000
11000
SuperCold filter doese↵ectively function as a coin Figure 12. The efficiency of just ARCONS, neglecting
Wavelength (Å)
Herewiththe 4a K
blackbodyradiationis blocked
ou
6 tw
stop
diameter
of
12
mm.
There
are
the
atmosphereandtelescope,
is
shown
as
the
red
dashed超伝導検出器
Sekimoto
Figure2014/12/4
4. The Y.opticallayout of ARCONS. Light enters ARCONS
thin piece of borosilicate glass coated in Indium
0.2

Fractional ThroughputsB. Mazin + 2012 Optics Express

Detector Quantum Efficiency

0|S21| (dB)

−5
−10
−15
−20
−25
4.23

4.24

4.25 4.26 4.27
Frequency (GHz)

4.28

0.6

0.4

0.2
0.0
200

500
1000
Wavelength (nm)

3000

100

Number of Resonators

Number of Resonators

80

0.8

60

40

20
0
30000

超伝導検出器 2014/12/4 Y. Sekimoto

60000
90000
Measured Q

120000

80
60
40
20
0
0

1

2
3
4
Nearest Neighbor (MHz)

5

6

7

Optical Coupling
Z0

Zsub
R

port 1

port 2L

Si substrate(t ~ 300µm)
Superconductive
thin film(t ~ 30nm)

λ = 1.5 µm
0.5

L
C

Absorption

0.4
0.3
0.2
0.1
0.0

0

100 200 300 400 500 600
R sheet resistivity @W per squareD

-0.78LENS ARRAY10

APO-Q-P222-F0.93mm

Table 1
ptical prescription for ARCONS.

Figure 3. Left: A microscope image of a portion of the 2024
pixel MKID array used at the Palomar 200” telescope. A microlens
focuses the light on to the 40⇥40 µm inductor. Various features ofinterest are labeled. Right: A zoomed in view of the array in theleft panel.
Mazin,etal. 2013,
125,
1348
Figure B.
6. A.
ARCONS
installed
at thePASP
Palomar200”.

(blue), 0.7
mensions ofd the rightrray. Even
contained“ARCONS:A 2024 Pixel
Opticalthrough Nearmagnetic
field remaining
in thesuperconducting
magnetrampsIRdown
from 0.75
kG to Spectrophotometer,”
0 kG over the 12 hours hold
Cryogenic
Imagingtime.

ir cooledfrom then a smallat can be
At Lick,
utside theAt the Palomar 200”, an aluminum frame is attached
to a steel plate in the Coudé antechamber that is used toaccommodate the Coudé spectrograph’s slit jaws. ARCONS hangs down from this aluminum frame, as shownin Figure 6.
At the Lick 3-m, ARCONS is also placed in the Coudé
antechamber, but since the Hamilton Spectrograph isstill in use the mounting plate is not used. Instead, ARCONS is hung from an I-beam in the ceiling and9 thenstabilized to the mounting plate with a steel strut.

uring thes ramped

4.2. Mounting to the Telescope

is
77
4
A
A
va
bu
w

co
to
bl
at
Su
st
m
th
ar
th
th
H

ARCONS:

B. Mazin, et al. 2013 PASP 125,12

ARCONS: Array Camera for Optical to Near-IR Spectrophotometry

14 000
14 000

12 000

12 000

10 000

Optical Counts

Optical Counts

10 000
8000

2000
0
0.0

Palomar 200”

0.5

2.0
1.5

8000
6000

6000
4000

Figure 14. A mosaic of the interacting galaxies Arp 147 made
ARCONS on the Palomar 200”. The data consists of 36
Figure with
14.
A mosaic of the interacting galaxies Arp 147 madepointing of 1 minute each. To make this image, the data waswith ARCONS
therays
Palomar
The datacalibrated,consistsandof 36
cleaned of on
cosmicand hot 200”.
pixels, wavelength
pointingflatoffielded.
1 minute
each. Tomakethisof image,the data
This processed
data
for eachthe 36 pointings
waswasin RA rays
and Dec
thepixels,
amount wavelength
requested by calibrated,
our mosaicingand
cleaned o↵setof cosmic
andbyhotcontrol
softwareandcombined.
No
fieldderotation
was
performed.wasflat fielded. This processed data for each of the 36 pointings
madeby breaking
the ARCONS
intoo↵set inThe
RAfalseandcolors
Dec wereby theamountrequestedby ourdata
mosaicing

Crab pulsar

11

4000
2000
0
0.0

0.5

1.0

Pulse Phase

1.0 1.5

Pulse Phase

Figure 16. The alignment of the radio (red) and optical (blue)
pulsesFigure
from the16.
Crab Pulsar
verify the absoluteofThe alignmentof the timing
radio accuracy(red) and
ARCONS.
pulses from the Crab Pulsar verify the absolute timi

ARCONS.
ARCONStiming performance was measured by simultaneously
observingtiming
the Crab
Pulsar with ARCONS
andARCONS
performance
was measur
the Green Bank Telescope (GBT). The data shown intaneously
observingtheCrab
Pulsarwith
AR
Figure16 shows that
ARCONSsees
an opticalpulse
leadtheradio
Green
Telescope(GBT).
The daing thepulseBankby about
150 µs, whichis consistent
withFigure
previous16
observations
et al.sees
2003).
shows that(Shearer
ARCONSan optica

September

Giga-z: A 100,000 OBJECTSUPERCONDUCTING SPECTROPHOTOMETER
FOR LSST FOLLOW-UP
D. W. Marsden, B. A.Mazin, K. OʼBrien, C. Hirata 2013 ApJSS 208:8•

R423nm = E/∆E = 30
Marsden et al.

ects
to
ong
ing
vey
eg2 ,
t al.
for
was

log
hift
and
RG
s is
of
by
hift
me
mits,
of
the
data

The Astrophysical Journal Supplement Series, 208:8 (15pp), 2013 Sept

Throughput

0.3
0.2
0.1
0.0
0.25
0.20
0.15
0.10
0.05

Figure 10. SDSS J001507.00−000800.9 quasar spectrum in black, at theresolution of Giga-z in red. This QSO has a redshift of 1.703.
(A color version of this figure is available in the online journal.)sion measurement of σ(w_p)
the matter power
spectrum as well
as BAOs σ(Ω_k)
σ(w_a)σ(Δγ)
at high redshift. Furthermore, quasars could be unambiguously
distinguished
LSST from stars. Besides BAOs and measurements of
0.03820.695
0.221
0.0252the distribution
photo-z of structure to z ≈ 6, Giga-z could also be used
to study the quasar luminosity function, quasar clustering andbias,Giga-z
set limits on the0.0348
quasar duty cycle,
and improve
our under- 0.0205
0.576
0.168
photo-zstanding of these objects and their evolution and co-evolution

0.00
400

600

800
1000
Wavelength [nm]

1200

1400

Figure 4. Simulated system throughputs for the LSST (top) and Giga(bottom) experiments, accounting for optical element (filter and lens) throughputs, mirror reflectivity, detector quantum efficiency, and atmospheric transmission. The LSST u, g, r, i, z, and y filter implementation (see Section 4.3
is based on the LSST Science Collaboration (2009) publication. The effectiv
Giga-z filter set is for devices with energy resolution R = 30 at 423 nm. Cutoffs are imposed at 350 and 1350 nm due to the effects of sky brightness an
atmospheric transmission constraints.
(A color version of this figure is available in the online journal.)

MKID: Microwave Kinetic Inductance Detector
1. Photons break cooper pairs and generate quasiparticles
2. Super conducting resonator senses a change ofkinetic inductance
3. Resonator frequency and amplitude changes
depending on a number of incident photons

Lens Array
Cooper pairs 2Δ Double Slot Antenna
3µmhνCoplanar Waveguide (CPW)Superconducting Resonators
-15
Dark
Light

quasi-particles
Pair Breaking Detector

S21 [dB]-20-25

P. Day et al. 2003 Nature
J. Zmuidzinas 2012 ARCMP

-30
-35
-40
4.056

4.058

12

4.060

4.062

F [GHz]

4.064

4.066

Microwave Kinetic Inductance Detector (MKID) P. Day et al. 2003 Nature
J. Zmuidzinas 2012 ARCMP
J. Baselmans 2012 JLTP
1
1
1
=
+
Qr
Qi
Qc

C
Marimba

C
nqp
1+
ns

Lk

Lk0
Cooper pairm
Lk0 =ns e 2 A
46

MKID2

MKID3

MKID2

6.378

6.382

MKID3

44

S21 [dB]

MKID1

MKID1

42
40
38

500 um

36
6.376

6.38

6.384

6.386

6.388

6.39

MKIDの特徴
Cooper pair breaking detector
ミリ波からX線まで

2= 74 GHzfg =hmateri Tc [K] Tb [K]
al
Al
1.2
0.24

Tc
1K
fg
[GHz]

88

低雑音 NEP < 5 * 10^{-18} W/rHz

Nb

9.3

1.9

678

広いダイナミックレンジ ~ 10^5

Ti

0.4

0.08

29

周波数多重化1000 素子 with a LNA

NbTiN

14

2.8

1026

TiN

(0.5) 4.5

0.9

330

14

220GHz-700 pixel MKID camera

T. Nitta et al. 201315

Crystal Aluminum on Si wafers
Molecular Beam Epitaxy

Al on Si (111) wafer
Thickness 160nm
Cleaning: BHF + 650 deg. (20 min)Back ground: 2×10^-8 Pa
Wafer: 75 deg.

RHEED

Al (111)Si (111)

M. Naruse et al. 2012 JLTD
“Development of crystal Al MKIDs by molecular beam epitaxy”

16

MKID noise
S( ,R)N EP ( ) =
q r

·

( ,R)
Nqp

1+

2 2 1/2
r

1+

1/2
2 2
res

M. Naruse et al. 2013 IEEE TSTNEP 6 x 10^(-18) W/rHz

17

読出回路と0.1K希釈冷凍機
大陽日酸

Readout 270 MHz/board → 1 GHz/board
Resonator 2MHz spacing → 500 pixel/board
16 us sampling

K. Karatsu + 2014 JLTP

18

50
新田冬夢 2014 筑波大

博士論文

46

584 / 608 (~ 95 %)Qi Distribution

histgram

S21 [dB]

歩留まり :

42
38

Entries
520
Mean 8.036e+04
RMS 1.617e+04

100

T(stage) =100 mK3480

検出器間隔：1~2 MHz

60

30

40

4

4.5

20
0
0

3

20

40

60

80

100

120

140

160
{Q}

×10

Q値
共振の鋭さを表すパラメータ

Mean (~ 105)
→高い値を得たS21 [dB]Counts600素子MKIDの評価

46

5
5.5
6
Frequency[GHz] [GHz]Frequency

6.5

44
42
40
38

一素子の検出器応答

36
6.355

6.363
19

6.371

6.379

Frequency [GHz]

6.387

6.395

Cosmic ray events•

τ=79.9μs•

a few events per an hour•

T. Okada et al. 2014•

1μs sampling

f=3.494GHzTime [ms]20南極望遠鏡筑波大学•東北大学
T. Tsuzuki et al. 2014 SPIE
Wide Field Optics Design(T.Tsuzuki et. al., SPIE (2014))

Cryostat

Cold Aperture Stop

•
•
•
•

10 m Antarctic Terahertz Telescope
Assemblage the 7 MKID modules
Frequency : 850 GHz
Detector focal plane¾ FoV : 1 deg¾ Diameter : 160 mm

1221

LiteBIRD
Lite (light) satellite for the studies of B-mode polarization and
Inflation from cosmic background Radiation Detection- 50 - 270 GHz ~ 600 pixel
Launch is planned in 2022
KEK, ISAS/JAXA, U. Tokyo, NAOJ
M. Hazumi et al. 2012 SPIE

E-modeB-modeInflation potential energy

r: tensor to scalar ratio

22Options for Higher efficiency
1. Optical Cavity
1.

S. Miki, et al. 2013 “High performance ﬁber-coupled NbTiN superconducting
nanowire single photon detectors with Giﬀord-McMahon cryocooler.,” Opt.
Express, 21, 10208

2. Multilayer AR
1.

Fukuda, D. et al., 2011 “Titanium-based transition-edge photon number
resolving detector with 98% detection eﬃciency with index-matchedsmall-gap ﬁber coupling.,” Opt. Express 19(2), 870

3. New Material
•

WSi

•

Ta based superconductor

超伝導検出器 2014/12/4 Y. Sekimoto23

Absorption efficiency, Pabsorb (%)

an effective structure to enhance the absorption Pabsorb of photons
nanowire. To verify the actual effectiveness of this structure, we sim
cavity structure and compared the results to a simple cavity structu
S. Miki, et al. 2013 “High[12].
performance
we used the software that en
For the fiber-coupledsimulation of NbTiN
Pabsorb, superconducting
nanowire single photon detectors
with Gifford-McMahon
cryocooler.,” multilayer
Opt. Express,
electromagnetic
behavior of single-period
gratings (Pho21, 10208–14
this software,
the incident wave enters the unit cell corresponding topolarization, and transmission as well as reflection can be calc
wavelength range. All of the designs that were used in the simulati
above. In the simulation, we used complex refractive indices as nSi =1.551, nNbTiN = 4.563 + i4.911, nAg = 0.322 + i10.99. These values weusing a spectroscopic ellipsometer, and constant values at 1550 nm w
100 nm thick Ag
250 nm thick SiO
5 nm thick NbTiN

100

100 nm 60 nm

270 nm thick SiO2

8060

Si Substrate

100 nm thick Ag m

250 nm thick SiO la
5 nm thick NbTiN

100 nm thick Ag
250 nm thick SiO
5 nm thick NbTiN

270 nm thick SiO2 l

100 nm 60 nm

MgO Substrate40

Si substrate
1400

1600

1800

Wavalength (nm)2000

Fig. 1. Schematic configuration of NbTiN SSPD on thermally oxidize

Fig. 2. Simulated Pabsorb of NbTiN SSPD devices on thermally oxidized Si substrate. For
comparison, Pabsorb of NbTiN SSPD on MgO substrate with simple cavity structure is also
shown in this Fig.
超伝導検出器 2014/12/4 Y. Sekimoto24

refractive index of the titanium film at 850 nm is n=3.95+4.13i at room temperature. The
cavity consistsof multiple
dielectric
layers of
SiO2 (n=1.48) and Ta2transition-edge
O5 (n=2.04) deposited photon
by
Fukuda,D. etal., 2011“Titanium-based
number resolving
ion beam assisted sputtering. A total of 7 layers are used for the AR coating, and 15 for thedetectorwith 98% detection
eﬃciency
index-matchedsmall-gap ﬁber coupling.,”high reflection
mirror (Reflectance>99.9%).
The thicknessesof withthese dielectricfilms
are designfor thecavitycurve with wgap=f is 0.06% (99.94% absorption in T
optimized Opt.
to obtainawide
spectralbandwidth
of
~40
nm
at
the
wavelengthofinterest
approximately 850 nm. The experimental values are slightly larger, however, and agr
Express 19(2), 870(λeff=850 nm). As shown in Fig. 1(b),  a  bare  optical  fiber  (outer  diameter  ~125  μm)  without  a  with the simulated reflectance for wgap=1.4×(λeff/4). A gap spacing of 1.4×(λeff/4) correa physicalthickness of 300 nm, which is consistent with the step height of 240 nm b
ferrule is coupled to the cavity from the front side. The fiber core position is toalignedto thethedevicesurface
center of the TES using back-side through-chip imaging with a microscope [11]. To form a and the niobium wiring, as shown in inset of Fig. 1(a). Thisa lift-off process during niobium wiring fabrication. It should be noted t
robust coupling, the space gap wgap between the fiber end and the device surfaceproduced
is filledbywith
measured reflectance is remarkably small at less than 0.5% over the wavelength rang
an ultraviolet-curable resin after the fiber alignment process. The refractive index(n=1.56) of
835 to 870 nm, which implies that the device has a high absorption efficiency of over
the resin is well matched to that of the fiber core (n~1.44). The spot size required
to range.
obtainBesides,ain thisno obvious fringes were observed during the reflectance measure
99% photon flux from the   optical   fiber   (MFD~5   μm   and   numerical   aperture~0.14)  is  which imply that the detection efficiency would have a flat spectral response in the obestimated  to  be  8  μm  assuming  wgap=1  μm.  Thus,  the  sensitive  region  of  the  TES  device  used  wavelength range. It is interesting that the reflectance for wgap=λeff/4 and 2×(λeff/4) gi
2upperor lower-limitof the intensity of interference fringes, respectively. Thus, the mahere  is  set  to  10  ×  10  μm with a thickness in 22 nm. The fiber alignment error isestimatedtoefficiency to  canbe  be obtained with wgap=2×(λeff/4). A similar efficiency enhancement ha
be less than   1   μm,   and   so   the   coupling   loss   due   to   such   misalignment   is   thought  previously reported [12].
negligible.

Fig. 1. (a) SEM image of a cross section of an optical TES cavity, produced by focused ion Fig. 2. The solid lines show simulation results of wavelength dependent reflectance for an
beam milling. The dark and bright layers represent SiO2 and Ta2O5, respectively. The Ti-TES optimized cavity and fiber-coupled devices with wgap values  of  λeff/4, 1.4×(λeff/4), 2×(λeff/4), 10
is located between the two red arrows. The upper surface is covered with a tungsten (W) layer μm,  30  μm,  and  infinity  (no  fiber  coupling).  The  circles  are the measured reflectance results foras protection against damage by the Ga+ ion beam during milling. The inset is an enlarged the fiber-coupled Ti-TES device, which agree well with the simulation results forview of the contact between the TES and Nb electrodes. (b) Cross-sectional schematic showing wgap=1.4×(λeff/4).
the optical-fiber coupling. The fiber is aligned under a microscope using back-side throughchip imaging. A gap with a thickness wgap between the exit end of the fiber and the surfaceof
3.2 Detection
efficiency
the antireflection layers is filled with an ultraviolet curable resin.

The total system DE for the fiber-coupled TES device is determined by irradiating thewith   extremely   weak   coherent   laser   pulses   with   a   mean   photon   number   μ i per pu
3. Results
determine   the   DE   for   different   values   of   μi, we compare the observed photon deprobability
withaPoissondistribution,
whichisexpressed[13
3.1 Photon absorption efficientn
PPoisson (n | Pi ) (KPi ) exp(KPi ) / n! , where η is the system DE and n is a number
The intrinsic photon absorption coefficient of the fiber-coupled cavity-embedded
TESstate.
devicephotonThe observed detection probability is calculated from the pulse height
25 spe超伝導検出器
Y. Sekimotois analyzed 2014/12/4
by performing
absolute reflectance measurements, and can be deduced
fromtheP (n | P ) S (n) / T , where S(n) is the summed count for photon state n and T is thre placed at a distance of 60 mm away fromets and maintained at room temperature. The
holder rotates during sputtering so that the films
uniform composition in a wafer.
r to sputtering, the native oxide on Si substrates
ed by dry etching, while the targets are cleaned
uttering. The inlet Ar gas flow is 50 cm 3 /minpressure• during sputtering is 5 x 10~3 Torr. Both
Tungsten-Siliconnd W - G e thin films are prepared with a variety
ositions• ranging
from0 to mK
90 at. % metalloid.
Tc (W)= 10
alloid content in the films is controlled by theer. The• film
thicknessand the deposition rate
150
μΩ-cm
substrates are about 500 nm and 0.07 nm/s,
vely. • low-pressure chemical
trical resistivity
calculated fromthe sheetvaporisdeposition(LPCVD)e and film thickness. The sheet resistance attungstenmperature isusing
measuredby a four-point probe. The
kness is measured
by masking
a part ofandthe film
hexafluoride(WF6)
suring thesilane
step heightwith a stylus apparatus(SiH4).
Instruments, alpha-step 200).
ow temperatures of 1.9 to 10 K, the electritance is measured by the four-point-probe d.c.
each time the temperature passes 0.05 K as
ng raised and reduced. The samples are cut
S. Kondo, 1991 “Superconducting characteristics
roximately
4 mm x 10 mm chips, to the surface
and the thermal stability of tungsten-based
h copperlead wires
are attachedindiumamorphousthin films,”
J. Mater.usingRes., 7,853
The sample temperature is monitored by a Gee thermometer.
stigations both by x-ray diffraction and by scan超伝導検出器 2014/12/4 Y. Sekimoto
ectronmicroscopy (SEM) are carried out to

2.Op

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26

WSi SSPDLETTERSOTONICS DOI: 10.1038/NPHOTON.2013.13
a 360
λ = 1,510 nm

240
180
120
60
0

0

60

120 180 240 300
Azimuth, 2εB (deg)360

SDE (%)

λ = 1,625 nm

300
Inclination, 2θP (deg)300
Inclination, 2θP (deg)

b 360

85

240

76

180
69

120
60
0

0

60

120 180 240 300
Azimuth, 2εB (deg)

360

c 100
SDEmax1.25
SDEminSDE (%)

R

1.20
1.15

80
1.10
70

SDEmax/SDEmin

90

the WSi film was deposited by cosputtering W and Si targets1, orby sputtering a
W0.55Si0.45 target, onto thesubstrate at room temperature.

1.05
1,520

1,540

1,560

1,580

1,600

1,620

Wavelength, λ (nm)F. Marsili,
et al. of2013
singleinfrared
photonswithefficiency,”
Nat. Photonics, 7, 210
on and wavelength
dependence
SDE. “Detecting
a,b, SDE (in colour
scale)
versus theinclination(2uP93%) and systemazimuth (21B) angles of then the Poincaré sphere at l ¼ 1,510 nm (a) and l ¼ 1,625 nm (b). The ratio between maximum and minimum values of the SDE (R ¼27
超伝導検出器 2014/12/4 Y. Sekimotoed from R ¼ 1.23 at l ¼ 1,510 nm to R ¼ 1.08 at l ¼ 1,625 nm because the wavelength dependence of the absorption of the optical stackO. Quaranta, T. W. Cecil, and A. Miceli, 2013 “Tungsten Silicide Alloys for Microwave Kinetic
Inductance Detectors,” IEEE Trans. Appl. Supercond., 23, 2400104.

W5 Si3 (Tc = 4K) and WSi2 (Tc = 1.9K) . The films were deposited using DC magnetron
sputtering from a single compound target onto both silicon and sapphire wafers.

EE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 23, NO. 3, JUNE 2013

WSi2 (Q=7.1x10^6)

ANTA et al.: TUNGSTEN SILICIDE ALLOYS FOR MKIDs

2400104

W5 Si3 (Q=1.7x10^5)

Fractional frequency shift of 100 nm (square) and 1 µm (circle) thickFig. 4. Phase pulses from Fe-55 x-ray in WSi2 (dashed line) and W5 Si3 (solid
CPW resonators on sapphire indicating a high degree of film uniformity line) CPW resonators on sapphire normalized to the same size to facilitate the
TC and α), which we believe is due to the uniform composition of the comparison. Both resonators show a pulse decay time of < 5 µs, which is
The lines
using thefraction
Mattis-Bardeen
Theory with
TC = asnear
Fig.are2. calculated
Kinetic inductanceof CPW resonatoron sapphirea the resonator lifetime, suggesting that the quasiparticle lifetime is actually
1.80
K, state
K, α = 0.92,
andofγ film
= 1 thickness
for the 100
nm film using(blue line)
and TTCC =shorter.
andnormalfunction
calculated
measured.53, andresistivities;
γ = 1/3 for1 µm film(black line).
openthesymbols
are calculated
values, filled symbols are measured|
data, line is a guide to the eye. Upper inset shows the transmission, |S21
with
TiN [13]. The resonators show a high degree of uniformity
28(red circles), past a WSi2 CPW resonator with 100 nm nominal thicknesses,
超伝導検出器2014/12/4OF
Y. Sekimoto
5
III.
MKIDS
T
UNGSTENSILICIDE
across
the
16
mm
chips
and
from
one
chip
to
another.
f = 1.766 GHz and Q = 7.1 × 10 as determined from Lorentzian fit (blueO. Quaranta, et al. 2013, “X-ray photon detection using
superconducting resonators in thermal quasi-equilibrium,”
Supercond. Sci. Technol., 26, 105021
Supercond. Sci. Technol. 26 (2013) 105021
O Quaranta et alngathedominant
conductances
andinterdigitatedlocations for x-ray100
nm thickthermal
WSi2 film(gray). The
capacitor (IDC) portion (green) is on solid SiN/Si substrate (500 nm/
Figure2.
The main figure shows pulse templates obtained byctancethroughthetheinductor
are not
shown. (red)(b) A lies
false-color
300 μm),while
inductive
meanderon the suspended SiN membrane (blue). The meander encircles ther is fabricated lithographically from a 100 nm
thick WSi220
film(gray). from 6 keV photons from the tantalum-300
averagingpulsesabsorber (yellow).
ubstrate (500 nm/300 µm), while the inductive
meander(red) lies
on mK. The blue dashed curve represents the 29
device
at
T
=
85
bath
超伝導検出器 2014/12/4 Y. Sekimotober (yellow).
The coplanar waveguide (CPW) feedline is shown inResolution at 1.5 um
material

Tc

Tbath

fg

NIR
resolution

K

mK

GHz

at 1.5 um

NbN

16

2286

1168

13

NbTiN

14

2000

1022

14

Nb

9.3

1329

679

17

Nb/Al

7.0

1000

511

20

TiN

4.5

643

329

25

WSi

4.2

600

307

26

TiN

1.1

157

80

51

Al

1.2

171

88

48

Al/Ti

0.7

100

51

63

Ti

0.40

57

29

84

超伝導検出器 2014/12/4 Y. SekimotoR== 0.57,1= 2.355hF

F = 0.2 Fano factor

30

まとめ
超伝導検出器
ミリ波サブミリ波
冷却が必須
MKIDは多ピクセル読み出しが容易
近赤外•可視•紫外線
低分散面分光高速読出
高い量子効率31