bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial Distribution of Blue Electroluminescence in ZnSe MIS Diodes
Authors: Xi-wu Fan , Ji-ying Zhang , Zhi-shun Zhang , Shou-yin Wang , An-de Lu , Wei-zhi Li , Jin-xiu Jiang , Yao-wu Sun
Published: February 2023

Spatial distribution of blue electroluminescence(EL) in ZnSe MIS diodes(1,2) using ZnS polycrystal film as an insulating layer has been studied. The diodes were fablicated by nominally undoped ZnSe crystals grown from the vapour phase in sealed capsules containing light excess of zinc(3).
Four Wave Mixing Spectroscopy of Mixed Crystals Using Three Input Frequencies
Authors: Steehler Jack K. , Nguyen Dinh C. , Wright John C.
Published: February 2023

Multiresonant four wave mixing provides information about each resonant level. Multiple resonances also provide sensitivity and selectivity. Specific methods for obtaining unambiguous information from two input frequency and three input frequency nonlinear experiments have been developed. Experimental data have been obtained for the single site pentacene in benzoic acid system, and for the four site pentacene in p-terphenyl system.
Study on the Renormalization Effects of Exciton Polaritons in CuCl by Non-Linear Ellipsometry
Authors: Kuwata Makoto , Nagasawa Nobukata
Published: February 2023

Recently, the optical bistability associated with the formation of excitonic molecules (EM's) has been studied intensively. For the quantitative analysis of this effect the non-linear change in the refractive index should be measured. Here we present a new method to measure this accurately.
Optical studies of Rare Earth ion pairs: interaction and energy transfer
Authors: Buisson R.
Published: February 2023

Rare earth ion pairs in isolators produce satellites for all optical transitions as a result of both the crystal field change induced at the site of each ion by its neighbour and the interaction between the two ions. The very narrow lines of diluted crystals make possible the selective excitation of these pairs and thus the direct study of the fundamental two ion mechanisms which are involved in transfer processes. Instead of measuring the average effect of transfer due to all classes of pairs, the rate can be measured for each class. The properties of concentrated crystals (a macroscopic result) can then be predicted from results obtained on pairs in a diluted sample (a microscopic measurement).
Self-trapping of Excitons in Rare-Gas Solids: Measurement of Self-Trapping Rates and Influence of Dimensionality
Authors: Roick E. , Gaethke R. , Gurtler P. , Zimmerer G.
Published: February 2023

See MB9 for summary.
Laser Excitation and Spin Coherence of Phosphorescent F 2 2 + Centers in CaO
Authors: Glasbeek M. , Casalboni M. , Vreeker R.
Published: February 2023

See TuG3 for summary.
The Jahn-Teller Effect
Authors: Elliott R. J.
Published: February 2023

Van Vleck developed the Jahn-Teller ideas to explain magnetic and optical properties of ions in crystal. The application to spectra will be reviewed.
Selective Excitation of Exchange-Coupled Cr3+ Pairs
Authors: McDonagh C M , Henderson B
Published: February 2023

Selective excitation of 2E → 4A2 fluorescence from Cr3+ ions in MgO using a tunable CW dye laser has revealed optical transitions which are not observed in direct absorption or fluorescence measurements. These lines are assigned to a new centre involving an exchange-coupled pair of Cr3+ ions. Fluorescence measurements as a function of concentration show that the pair of lines at 698.9 nm and 703.5 nm arise from a tetragonally symmetric pair configuration. The assignment of these optical transitions to the system Cr3+ - VAC - Cr3+ has now been confirmed by an EPR study1. Selective laser excitation in this spectral region indicates the presence of another optical spectrum which almost overlaps that of the Cr3+ - VAC - Cr3+ system, and which also exhibits tetragonal symmetry. A number of lines are observed from 698.7 nm up to the region of the cubic R-line at 698.1 nm due to the higher 2Ev orbital state of this new centre. The splitting due to the lower 2E transition 2Ev transition is not as readily observed partly because of the greater overlap with the Cr3+ - VAC - Cr3+ transitions. The data have been fitted to a configuration involving two Cr3+ ions in next nearest neighbour positions in a <100> crystal direction. The exchange coupling in the ground state is antiferromagnetic as is expected for Cr3+ ions.
Dynamical Jahn-Teller Effect On The Triplet States 4T2(D) of Mn++ in polymorphic ZnS
Authors: Parrot R. , Naud C. , Curie D. , Gumlich H.E. , Busse W. , Pohl U.
Published: February 2023

New experimental andtheoretical results have been obtained for the orbital triplet states 4T2 arising from the spectroscopic term 4D of the d5 configuration of Mn++ in polymorphic ZnS.
Tunneling Luminescence in Zinc Silicate Doped with Gallium
Authors: Hess H. , Kahlert H. , Krautz E.
Published: February 2023

When zinc silicate with a violet luminescence peaked at 370 nm is doped with gallium in concentrations of 1).001 2).005 3).2 4)1.0 mol % gallium oxide a new emission band with a maximum at 420 nm is established as shown in Fig. 1. The separation of both superimposed emission bands is possible because of their different luminescent decay times. By such doping additional traps are introduced as could be proved by the thermal glow curves for the 1) 0 2). 01 3) .2 mol % gallium oxide concentrations after a 4 minute excitation with 220 nm and a heating rate of 14 K/min as shown in Fig. 2. The doped samples are distinguished by an increased light sum and photoconductivity. The red shift of the time-resolved emission spectra for zinc silicate doped with .8 mol % gallium oxide at 20 K as shown in Fig. 3 allows to assume that radiating donator-acceptor-pair transitions i.e. radiating tunneling processes between shallow traps and excited activator centers are involved in the charge recombination process. This is in agreement with the results shown in Fig. 4a, where the time dependence of the temperature (1) and the luminescence (2) of the doped sample after excitation with 250 nm at 100 K are compared. Below 50 K a remarkable increase in luminescence intensity is observed. The number of electrons thermally released from the shallow traps is certainly small at these low temperatures. This behaviour is also seen in Fig. 4b, where the cooling process has been interrupted by short periods of heating. In the range between 45 K and 60 K the decay of the luminescence is temperature independent, which demonstrates that no thermally stimulated recombination occurs. The additional luminescence can therefore be explained only by electron tunneling from shallow traps to excited activator centers.
Site-Selection Spectroscopy Of Eu3+ Ions In Different Types of Glasses
Authors: Gang Xu , Rowell Richard C.
Published: February 2023

Laser time-resolved site-selection spectroscopy measurements were used to characterize the properties of Eu3+ ions in seven types of glass hosts including oxide glasses of lithium phosphate, lithium silicate, sodium silicate, potassium germanate, lithium borate, and europium pentaphosphate as well as the fluoride glass ZBLA. The 7F0-5D0 transition was resonantly excited and the results were obtained by monitoring the 5D0-7F0 fluorescence which has not been done in most previous work of this type because of laser scattered light. This was overcome by the use of a fast electronic shutter. Measurements were made of the spectral structure, fluorescence lifetime, inhomogeneous linewidth, fluorescence 1ine-narrowed (FLN) width, and energy transfer rate parameter as a function of host composition, temperature, and excitation position within the inhomogeneous line.
Photoluminescence in obliquely deposited a-GeSe2 films
Authors: Koós M. , Somogyi I. Rósa
Published: February 2023

Obliquely deposited thin films of the a-GexSe1-x system have gained widespread interest as high resolution photoresists [1]. This paper reports the results of our photoluminescence (PL) studies of a-GeSe2 thin films deposited simultaneously at 0, 10, 30, 50 and 70° angles of incidence. Examination of the PL characteristics were carried out to throw light on changes in the electronic structure and the distribution of the radiative recombination centres induced by the columnar structure of these films and their gradual disappearance upon prolonged illumination.
Coherent Singlet Polariton to Trap Energy Transfer in Naphthalene Crystals
Authors: Small Gerald J. , Stevenson Sylvia H. , Connolly Maureen A.
Published: February 2023

One-photon studies of coherent energy transfer are hampered by the fact that excitons of well-defined and different wavevectors (k) cannot be prepared in the bulk. In addition, the group velocities of the excitons in molecular crystals and semiconductors are typically low so that even momentary exciton self-trapping can lead to coherence loss over short distances.
Luminescence Associated with Free and Bistable Self-Trapped Excitons in ß-Perylene
Authors: Nishimura H. , Mizuno K. , Matsui A.
Published: February 2023

The luminescence spectra in ß-perylene crystals reveal a strange temperature dependence1) (Figure 1). Analysis of the spectra provides clear evidence that at high temperatures the free exciton luminescence and the deeper self-trapped exciton luminescence dominate, while at low temperatures the shallower self-trapped exciton luminescence dominates.
Facile Nonphotochemical Hole Burning and Filling of Laser Dyes and Rare Earth Ions in Deuteroxy and Hydroxy Polymers
Authors: Fearey Bryan L. , Carter Thomas P. , Small Gerald J.
Published: February 2023

Nonphotochemical hole burning (NPHB) has been well established as a method of investigating the microscopic properties of doped amorphous solids, typically molecular impurities in organic glasses and polymers or rare earth ions in hard inorganic glasses1. The NPHB of ionic dye molecules in hydroxyl-lated polymer films recently has been shown to be significantly more efficient than many other systems2 and the temperature dependence of the optical dephasing of one such system has been reported3.
Resonant Light Scattering and Hot Luminescence at the Indirect Gap in BiI3
Authors: Karasawa T. , Komatsu T. , Kaifa Y.
Published: February 2023

See MB43 and MB44 for summaries.
Conservative-Dissipative Behavior of CO2 Laser with Injected Signal
Authors: Politi A. , Oppo G.L. , Badii R.
Published: February 2023

Class B lasers1 are described by the so called rate equations for field intensity and population inversion. A suitable nonlinear transformation shows that such equations are fully equivalent to a Toda oscillator with intensity dependent losses2. More precisely, the dissipative terms are proportional to the square root

ε
=

γ
η

/
k

of the ratio between the decay rate γ
η
of population inversion and k of field intensity. In many physical cases (CO2, Nd-Yag etc.) ϵ is ≪1, and the motion, within a first order approximation, is a conservative one. By extending such approximation to the case of an externally injected laser, we obtain a reversible model, that is, a flow invariant the composition of time reversal and a suitable reflection R of coordinates3. Reversibility implies conservativity only with the further assumption that any trajectory is invariant under R-reflection. In particular we have observed that, for critical values of the external amplitude, global symmetry-breaking (SB) transitions occur. More precisely, finite regions in the phase space change their structure from a conservative to a dissipative one. Consequences of these critical phenomena can also be revealed in the original physical system. In fact, the SB yields a stability of the orbit much stronger than that owed to the dissipative terms here neglected.
Instabilities in the Propagation of Laser Beams Through Atomic Vapors
Authors: Boyd Robert W. , Gauthier Daniel J. , Malcuit Michelle S.
Published: February 2023

There are several nonlinear optical processes that can lead to instabilities in a laser beam as it propagates through a nonlinear optical medium. Self focusing effects, for instance, can lead to the growth of new spatial frequency components in a laser beam. A laser beam can also be unstable to the growth of new spectral components. Stimulated Raman scattering is a well-known example of a process that can lead to this sort of instability. In this paper, we present the results of a series of experiments on the somewhat different instabilities that occur for the case of the propagation of a laser beam through an atomic vapor. We find that these instabilities become particularly pronounced when the frequency of the incident laser is near to that of a one- or two-photon resonance of the atom. In either case, we find that the laser beam is unstable to the growth of new frequency components, and that in general these new frequencies are not emitted collinearly with the incident laser. These instabilities are important because they place a limit on the laser intensity that can be used to drive nonlinear optical processes.
Multiple Isolated Branches in Four-Wave Mixing Optical Bistability
Authors: Kaplan A. E. , Law C. T.
Published: February 2023

H. G. Winful and J. H. Marburger 1 have first proposed an optical bistability with hysteretic response in collinear degenerated four-wave mixing. We show here the feasibility of multistable nonhysteretic behavior and isolated branches in the system considered by them. We consider two counter-propagating optical beams along z axis with the same frequency such that the total electric field is:

E
→

=

[

E
→

1

exp
(
ikz
)
+

E
→

2

exp
(
−
ikz
)

]

e

−
i
ω
t

where

E
→

1

and

E
→

2

are envelope vectors of forward and backward waves respectively. Based on 2, the nonlinear component of electric displacement

D
→

NL

in a Kerr-like medium can be expressed as:

D
→

NL

=

ϵ
o

χ

[

A

E
→

(

E
→

⋅

E
→

*

)

+

B

E
→

*

(

E
→

⋅

E
→

)

]

where ϵo is a linear electric permittivity of medium, χ is a constant of nonlinear interaction for a single linearly polarized plane wave, A and B are dimensionless constants dependent upon the particular mechanism of nonlinearity. Decomposing

E
→

1

and

E
→

2

into a sum of two circularly polarized components:

E
→

j

=

1

2

[

u
j

(

e
^

x

+
i

e
^

y

)

+

v
j

(

e
^

x

−
i

e
^

y

)

]

,
 
(
j
=
1
,
2
)

and using the vectorial nonlinear wave equation for

E
→

1

and

E
→

2

(Ref. 3), one can obtain four conservation relationships, which have four invariants of motion: I1 and I2 (total intensities of both of the beams) and two additional invariants referred below as M and J.
Stabilization and Passive Mode Locking of CW Alexandrite Lasers
Authors: Harter D.J. , Band Y.B. , Samelson H. , Ippen E.P.
Published: February 2023

Alexandrite is a solid state laser material which lases in the range of 700-800 nm. Alexandrite has been lased continuously by pumping with a krypton ion laser1 and by pumping with xenon and mercury arc lamps2. When alexandrite is pumped with the krypton ion laser, the output is very stable and, when the pump source is removed, the output damps through population oscillations which can be well described by rate equations3. However, when alexandrite is pumped by the xenon or mercury arc lamps, the output is very noisy at certain pumping levels. Experimental data showing this noisy operation will be presented and sources of this noise will be discussed.
Quantum Fluctuations and the Lorenz Equations
Authors: Sarkar Sarben , Satchell J S , Carmichael H J
Published: February 2023

The quantization of the Lorenz equations is shown to take the form of two complex and one real stochastic differential equations with multiplicative noise. Phase diffusion is the dominant feature for small values of the noise. Quantities such as the probability of the modulus of the variables are unchanged from those in the classical Lorenz equations. Moreover a unique fractal dimension can be associated with the stochastic process. For large noises there is a radical breakdown of this picture.
Effect of Noise on the Bifurcations to Chaos in a Modulated Diode Laser
Authors: Winful H.G. , Chen Y.C.
Published: February 2023

It has been demonstrated theoretically that a diode laser, when directly modulated at a rate comparable to its relaxation oscillation frequency, exhibits a period-doubling route to chaos1. This prediction was based on a numerical solution of the deterministic noise-free rate equations that govern the interaction between electrons and photons in the laser. However, it is known that the output of a cw diode laser can exhibit large amplitude fluctuations with a frequency centered at the relaxation oscillation resonance2. These fluctuations arise from the quantum nature of spontaneous emission and cannot be eliminated in real diode lasers. In effect, the laser acts as a noise-driven relaxation oscillator. In this paper we consider the effect of quantum noise on the predicted bifurcations to chaos of directly modulated diode lasers.
Experimental studies of transient noise-induced bistability
Authors: Lange W. , Mitschke F. , Deserno R. , Mlynek J.
Published: February 2023

The role of external noise in the process of critical slowing down (CSD) has been analysed theoretically by Broggi and Lugiato/1/; these authors recently predicted a transient noise-induced optical bistability due to amplitude fluctuations in the light input. They found that under conditions of CSD the probability distribution of light field amplitudes becomes double-peaked in a sizeable time interval during the approach to the single-peaked steady state distribution. Moreover they found that in the presence of fluctuations the delay times τD observed in an experiment on CSD should have a broad distribution, which can be very asymmetric. With increasing noise levels the mean value of the delay time should be considerably shorter than in the deterministic case.
Optical Instabilities Driven by Colored Noise
Authors: Hanggi Peter , Moss Frank
Published: February 2023

Over the last years, there has been steadily growing interest in nonlinear systems in which the nonlinear coupling can induce phenomena such as a Hopf bifurcation, bistable behavior or chaos1). Here our focus will be on nonlinear, noisy optical systems which either undergo a continuous Hopf bifurcation or exhibit bistability. The control parameters may also be subject to fluctuations. Using the standard assumption that those fluctuations evolve on an entirely different time scale, one usually approximates the noise by white (Gaussian) fluctuations. Typical examples are the treatments of the single mode laser2) or a dye laser3) at threshold. Above threshold, the whole matter can complicate considerably. In particular, it has been realized recently, that finite noise correlation effects, e.g. in pump laser fluctuations4) or in noisy external driving laser fields, can play a crucial role. Because optical systems exhibiting bistability5,6) are particular sensitive to the details of the noise properties; as is manifested by the exponential suppression of probability of the locally unstable state, those systems are quite suitable to put to a critical test various different theories and approximations.
The Lorenz Model
Authors: Sparrow C.
Published: February 2023

The three-dimensional set of ordinary differential equations, known as the Lorenz equations were first introduced by Ed Lorenz [2] in 1963 as a model of convection in a two-dimensional cell. Since then other authors, e.g. Haken [1] have shown that the same equations can be derived from the Maxwell-Bloch equations for single-mode lasers with damping. The equations are of mathematical interest because of the wide variety of behaviours that they display -- including chaotic behaviour and the existence of strange attractors -- for different values of the three parameters r, σ and b. It seems that the relevant range of parameters for laser applications is σ < b + 1 which, it must be confessed, is not the parameter range of greatest interest from a mathematical point of view. However, providing 3σ - 1 > 2b attracting chaotic behaviour will still occur [3,4] though it will occur at parameter values for which the equations also have stable stationary points and these may determine most of the observed behaviour of the system.
Instabilities of a Passive All-Optical System Subjected to cw Laser Light
Authors: Gibbs H. M. , Tai K. , Moloney J. V. , Hopf F. A. , LeBerre Martine , Ressayre Elisabeth , Tallet Andrée
Published: February 2023

A transverse optical bistability is defined here as a bistability that would not occur with a plane-wave input; it is characterized by pronounced changes in transverse profiles, but not in total transmission.1-5 In order to use transverse bistabilities to study instabilities of the type first studied by Ikeda6 for a ring cavity, one needs a medium response time τM less than the round-trip time tR between the medium and the feedback mirror. Here instabilities are studied experimentally using a short length of sodium vapor and a far-field mirror (Fig. 1).7,8 This system has advantages over previous9,10 all-optical passive systems for studying instabilities: its input is cw, permitting the study of slowly evolving waveforms; it has little sensitivity to laser frequency shifts, because it has no cavity; its optical nonlinearity arises from a vapor of one-electron atoms, giving hope for a detailed quantitative comparison of experiments and calculations.
Analytic Studies of the Laser With a Saturable Absorber
Authors: Erneux Thomas
Published: February 2023

In the laser with a saturable absorber (LSA), the spontaneous and stimulated emissions build up in the laser cavity but are restrained by the intracavity absorber. As a result, two new modes of operation are observed: optical bistability and time-periodic intensity pulses. These two behaviors are not observed in the usual laser under normal conditions. Thus, the LSA is an example of an active system displaying optical bistability. (See Ref. 1 for a general review).
Transient Bistability in a Laser Containing a Saturable Absorber
Authors: Arimondo E. , Gabbanini C. , Menchi E. , Dangoisse D. , Glorieux P.
Published: February 2023

The question of the behaviour of the LSA when a control parameter is a slowly varying function of time, has recently been raised [1]. The investigation of the transient behaviour of a LSA is interesting not only in connection with the problem of the response time of optically bistable systems but also because in any real experiment, if one wants to explore a phase diagram, the parameters have to be changed in time. Although the relaxation times of the molecular medium and the cavity response time are of the order of 100μs or smaller, the time constants characterising the transient regime of the LSA may be much longer because of the critical slowing down which appears near the limit points of the hysteresis cycle[2]
Theory Of An All-Optical AM-FM Modulator
Authors: Meystre P. , Reiner G. , Wright E. M.
Published: February 2023

Phase conjugate resonators (PCR) are optical resonators in which (at least) one of the mirrors is a phase-conjugate one (PCM), e.g. a four-wave mixing cell. These systems are of considerable experimental and theoretical interest, specially in view of their potential to eliminate phase distorsions within the resonator1. In recent work2, we discussed a PCR consisting of a Fabry-Perot resonator with one end mirror replaced by a lossless Kerr medium of infinitely fast response time pumped by two counterpropagating beams of same frequency. We described the PCM within the Raman-Nath approximation3, but including fully the effects of pump depletion. The normal mirror was positioned such as to couple the first order scattered field back into the PCM. We found that this system can break into self-oscillations corresponding to the half-axial modes predicted by linear theories1,4. For higher pump intensities, this is followed by a sequence of bifurcations to chaos, with in general the coexistence of several basins of attraction. We also showed5 that the first of this sequence of bifurcations is in general already sufficient to induce a quasi-periodic motion of the intracavity field phase, leading in practice to its complete indetermination.
Interaction between instabilities, phase instabilities, phase turbulence
Authors: Coullet P.
Published: February 2023

We review universal aspects related to instabilities. The classification presented rely upon the analysis of generalized Landau and Laundau-Ginzburg equations which describes these instabilities.
Phase Diagrams for CO2 Laser with an Intracavity Saturable Absorber
Authors: Arimondo E. , Gabbanini C. , Menchi E.
Published: February 2023

The infrared CO2 laser with an intracavity saturable absorber (LSA) is a system where instabilities in the nonlinear operation may be easily explored. Experimentally the LSA presents a bifurcation between states with time independent laser intensity, i.e. a bistable regime. Furthermore it presents bifurcations to states where the electric field amplitude is modulated in time with a period determined by the relaxation parameters of the laser medium and of the absorber. The modulation should be classified by its amplitude, as large or small. The large amplitude case, where the laser output is composed by pulses with amplitude constant when the bifurcation point is approached, corresponds to the passive Q-switch (PQS) operation, well known from the early development of the CO2lasers. In the small amplitude case the laser output power presents a sinusoidal modulation whose intensity decreases to zero when the bifurcation point is approached.
Generation of Squeezed States by Four-Wave-Mixing in a Cavity
Authors: Slusher R.E. , Yurke B. , Hollberg L. , Mertz J. C.
Published: February 2023

Phase dependent nonlinear optical processes can make large fractional changes in the phase and amplitude of an optical field. An example is the prediction(1) that four-wave-mixing can generate squeezed states of an optical field where the variance in the two quadratures of the field are unequal. In order to observe squeezed states and utilize them in interferometric measurements this inequality in variances must be large (e.g. ≳ 50%). The large phase shifts required to achieve this regime of squeezing can be obtained near the threshold for oscillation of four-wave-mixing in an optical cavity. (2) This paper describes an experimental study(3) of four-wave-mixing in a cavity near threshold using the nonlinear index of the Na atomic resonance.
Parametric Bistable Resonance in the Four Wave Interaction in Molecular Systems
Authors: Ratajska-Gadomska B. , Gadomski W.
Published: February 2023

Nonlinear optical processes due to the interaction of the vibrational modes in crystals (molecules) with external fields are usually described in terms of the nonlinear polarization of the medium. This polarization can be expressed as the power series of the small vibrational amplitudes, which are generally dependent on the external field intensity. In the procedures most frequently used the polarization is expanded only to the first order. The vibrational amplitude of the mode resonantly coupled to the field is found as the solution of the equation of the driven and damped oscillator (e.g. CARS).
Instabilities of Self-Pumped Phase-Conjugate Laser
Authors: Pare C. , Piche M. , Belanger P.A.
Published: February 2023

Optical chaos has recently been observed in a phase-conjugate laser1 (PCL) where phase conjugation was obtained by degenerate four-wave- mixing in BaTiO3. This complex dynamical behaviour is not predicted by a simple third-power law for the phase-conjugate mirror (PCM) reflectivity. A nonlinear theory by Wright et al2 has also confirmed the possibility of optical instabilities in a PCL with external pumps and without a saturable gain medium.
Period Doubling Bifurcations From a Linear (Empty) Interferometer
Authors: Brecha R.J. , Orozco L.A. , Rosenberger A.T. , Kimble H.J. , Carmichael H.J.
Published: February 2023

In investigations of dynamical instabilities in passive nonlinear optical systems it is often the case that the basic frequencies of oscillation which appear in sequences of dynamical states are those characteristic of the linear relaxation processes of one of the components of the nonlinear system. For example, in the single mode instability in optical bistability the frequency which occurs in the first bifurcation from a time independent steady state is approximately that of the cavity mistuning1, which is likewise the frequency observed in the transient relaxations of the cavity alone. For multimode instabilities that have been discussed by Ikeda and others2,3 the frequencies which occur at subharmonics of the cavity free spectral range are the same as those one can observe in the transient excitation of an empty linear interferometer. Because of this feature it is often difficult to separate nonlinear dynamical behavior observed in the transient regime from the simple transient oscillatory behavior of a linear system.4,5 An essential characteristic of the nonlinear interactions between the individual components is to stabilize what would otherwise be transient oscillations, and in fact to create new time dependent steady states.
The passive mode locking of an Nd3+:YAG laser with a two-photon absorber
Authors: Lawandy N. M. , MacFarlane D. L.
Published: February 2023

Recently, Badziak and Tyl [1] have theoretically analyzed the inclusion of a two-photon absorber along with a single photon absorber in a laser cavity. They predicted that mode locking would occur with an increase in the intensity and contrast of the pulses, and a reduction in the pulse length. In this paper we announce the experimental observation of passive mode locking in a pulsed Nd3+:YAG laser with the inclusion of only a two-photon absorbing element in the cavity.
Frequency Pushing In Lasers With Injected Signal
Authors: Oppo G.L. , Politi A. , Lippi G.L. , Arecchi F.T.
Published: February 2023

The synchronization of coupled oscillators is a very old problem1; the simplest quantum optical example is, perhaps, offered by laser with injected signal. In fact, the injection technique has important applications, since it offers an efficient way to lock high power lasers to an external frequency reference. On the other hand, the recent studies on laser instabilities and chaotic dynamics2 extend the physical interest to the unlocking parameter region.
Subharmonic Bifurcations and Irregular Pulsing Behavior of Modulated Diode Lasers
Authors: Chen Y.C. , Winful H.G. , Liu J.M.
Published: February 2023

The problem of existence of lasing regimes characterized by an irregular response of a semiconductor laser to a periodic modulation of the injection current has been of considerable interest recently. Based on coupled nonlinear rate equations for carrier and photon densities, Lee et al (1) predicted a period doubling route to chaos in a directly modulated semiconductor laser as the modulation index increases. Kawaguchi(2) showed a similar route to chaos in the optical response of a directly modulated, self-pulsating semiconductor laser with a saturable absorber. While chaotic behavior has been experimentally observed in other lasers with modulated parameters3,4, chaos in a modulated diode laser still remains to be demonstrated. In this paper we report the observation of a subharmonic bifurcation and erratic behavior in the output of diode lasers subjected to deep modulation of the injection current. The experimentally measured bifurcation sequences differ considerably from the predicted scenarios. Non-deterministic quantum noise sources are believed to play an important role in the observed phenomena.
Mask Synthesis for Diffraction-Limited Waveguide Luneburg Lenses1
Authors: Yao S. K. , Anderson D. B. , Oania C. M. , Kreismanis V. G.
Published: February 2023

An integrated optical circuit for RF signal spectral analysis requires a near diffraction-limited lens to perform the Fourier transform.1,2 A thin-film waveguide Luneburg lens3 using Ta2O5 in the lens region with Corning 7059 waveguide on thermally-oxidized silicon substrate is a low-cost approach providing for integration with a surface elasto-optic spatial modulator and a waveguide coupled photodetector array in the substrate. Waveguide Luneburg lenses are formed by sputtering high-index films through a circular mask with a shaped edge.
Thin Film Detectror for Integrated Optical Systems (‘)
Authors: Calì C. , Daneu V. , Riva-Sanseverino S.
Published: February 2023

A simple thin film detector for integrated optical systems is
described. This device has been fabricated by thin film techniques and
it can be built on any dielectric substrate, either prior to formation
of the optical wavaguide or deposited on waveguides grown by different
techniques (ion exchange, LPE, MBE, etc.)
Densely Packed Electrooptic AlyGa1−yAs−AlxGa1−xAs Rib Waveguide Modulators and Switches
Authors: Reinhart F. K. , Shelton J. C. , Logan R. A.
Published: February 2023

Rib waveguides (RWG) formed on single heterostructure Al
y
Ga1−
y
As−Al
x
Ga1−
x
As slab waveguides1 provide a simple and powerful means to achieve the routing requirements of monolithic integrated circuits. The design, fabrication and use of single mode RWG is discussed here in the context of uniquely high lateral packing density and the use of efficient electrooptically controlled phase modulators for switching applications. The RWG are conveniently formed as an added processing step after epitaxial layer growth, requiring only layer thicknesses and compositions suitable for single slab waveguide modes. Doping levels of either type is only required to be ≲ 1017cm−3 and is compatible with future monolithic integration with cw operated lasers. The RWG are electrooptically modulated by applying voltages between metal electrodes overlaying a buffering oxide layer and the substrate.2 The RWG are modulated by the depletion layer field of the semiconductor which does not require a particular doping type. Close overlapping of the depletion layer field with the optical electric field leads to very efficient modulation. The profile of the high index waveguide layer and the respective effective indices for fundamental TE modes at 1.06 μm are shown in Fig. 1. This simple step waveguide model serves as a design guide for the RWG modes. Fig. 1 represents a coupled pair of RWG that serves as the basis of a switch. The effective refractive indices for a step height of 700 Å differ by 0.004. This provides sufficient lateral guiding and permits up to 3.5 μm wide ribs that can carry only one mode per polarization.
Dual Beam Laser: A Gaas Double-Cavity Laser with Branching Output Waveguides
Authors: Merz J. L. , Logan R. A.
Published: February 2023

A new device is reported in this paper which incorporates a branching taper within the optical cavity of a GaAs double heterostructure (DH) injection laser as shown in Fig. 1. Dual output waveguides are therefore provided at one of the mirrors. The coupled cavities resulting from this configuration tend to suppress all but one dominant longitudinal mode. By suitable variations of layer thickness and/or composition, the device operates either as a tapered power divider (TPD), branching the incident power of a single mode into the two output arms of the device, or as a tapered mode splitter (TMS), diverting different transverse modes into different arms. We have achieved power ratios of between 4:1 and 5:1 for the TPD, oscillating in a dominant longitudinal mode at λ ≈ 8850 Å. For the TMS, a transverse mode at λ ≈ 8780 Å exits from one output arm of the device, while another transverse mode at λ ≈ 8550 Å is observed from the other; the relative intensity of these two output beams can be varied by changing the injection current.
New Microoptical Switches for use with Fiber Optical Transmission Lines
Authors: Giallorenzi T. G. , Burns W. K. , Steinberg R. A.
Published: February 2023

As has been recently recognized,(1-4) the polarization properties of integrated optical switches/modulators are of paramount importance in determining the usefulness of these devices in single mode fiber optic data transfer systems. In particular, these switches/modulators must perform efficient, complete switching of light regardless of state of incident polarization. These requirements result from the fact that linearly polarized light coupled into single mode, circular fibers suffers a rapid conversion to other polarization states, with the light emerging being generally elliptically polarized. Therefore any new switch design must be capable of polarization independent operation in order for it to be considered useable. In this paper, we report on the principals of polarization independent operation and describe the fabrication of the first polarization independent switch.
Thin Film Bragg Switch
Authors: Chen B. , Barnoski M. K. , Meijer C. M.
Published: February 2023

Recently, we reported an optical switch design based on the Bragg deflection of guided beams between two crossed single mode channel guides.1 The problem of low deflection efficiency (20%) was attributed to the presence of Li2O out-diffusion waveguide and lack of dielectric buffer layer. This paper discusses the latest results of performance of an improved switch device. Li2O out-diffusion modes were suppressed by LiNbO3 powder treatment and a 1000 Å thick SiO2 coating was employed to isolate the optical beam from the metal electrode.
Chemical Control of Optical Damage in Lithium Niobate
Authors: Holman R.L. , Cressman P.J. , Revelli J.F.
Published: February 2023

Lithium niobate, LiNbO3, has long been considered a promising electro­optic material. The development of high quality LiNbO3 optical waveguiding layers1 has stimulated demonstration of many low voltage, high speed optical devices. However, an interaction occurring between the laser and the crystal known as optical damage2 has severely limited their practical application.
Optical Surface Waves in Perfect and Imperfect Periodic Layered Media*
Authors: Yeh Pochi , Ng Willie , Yariv Amnon , Chen Pei C. , Cho A. Y.
Published: February 2023

Optical surface wave propagation along the surface of a GaAs-AlGaAs multilayer stack has been observed. The samples were grown by MBE as well as LPE.
The National Research and Resource Facility for Submicron Structures at Cornell
Authors: Ballantyne Joseph M.
Published: February 2023

Cornell University has received a grant for $5,000,000 over a five year period to establish on its Ithaca campus the National Research and Resource Facility for Submicron Structures. This unique facility will be a resource for developing and applying technology for producing submicron patterns, and will provide a new focus for workers in this field at Cornell and in other university, government, and industrial institutions.
Coherent Mode Coupling at Waveguide Bends
Authors: Taylor M. J. , Taylor H. F.
Published: February 2023

Bending losses are an important consideration in the design of integrated optical circuits, since some of the suggested device configurations will require directional change in interconnecting waveguides. It has been predicted that a directional change accomplished by two successive corner bends can have much lower attenuation than a single corner bend1. The lower loss is a consequence of coherent mode coupling at the bends. This paper presents experimental results on the optical transmission of waveguides with two bends which are consistent with this prediction.
Multiport Coupling Between Single Mode Fibers and Indiffused Channel Waveguides
Authors: Hsu H. P. , Milton A. F. , Burns W. K. , Sheem S. K.
Published: February 2023

We report the development of a flip-chip end fire coupler which provides efficient coupling between an integrated optics LiNbO3 channel waveguide chip and a number of single mode fibers. The design shown in Fig. 1 uses a silicon preferentially etched groove fiber positioner.(1) Alignment is accomplished in a single step by viewing through the transparent LiNbO3 which has been polished on both sides and aligning indiffused registration stripes on the LiNbO3 with narrow registration grooves etched into the silicon wafer. A special purpose aligner is used for this purpose. To complete the coupler fibers are pressed into the grooves on the silicon wafer. In our experiments the square corner end surface of the channel waveguide was prepared by cleaving the LiNbO3 crystal.
Borosilicate Single Polarization Fibers
Authors: Ramaswamy V. , French W. G. , Shiever J. W.
Published: February 2023

Demonstration of highly birefringent single-mode fibers[1,2] that maintain linear polarization points to the use of single-mode fibers together with polarization sensitive optical devices as well as other applications such as fiber gyros[3] non-linear optics[4] etc. The output polarization and its orientation at the end of long length low birefringence fibers[5,6], vary erratically due to minor stresses and changes in ambient conditions that couple energy between the nearly degenerate orthogonal modes.
Geodesic Optics: New Components
Authors: Sottini S. , Russo V. , Righini G.C.
Published: February 2023

Several reliable elementary components for integrated optics have been already built and tested, but only few of them are compatible with multimode operation. At the same time, the problem related to hybrid integration of the different components have limited so far the implementation of more complex circuits.
Low-threshold-current injection laser with built-in passive waveguiding
Authors: Amann M.C. , Stegmüller B.
Published: February 2023

Low threshold current as well as stable transverse monomode emission are basic requirements for application of the injection laser in optical communications. Low threshold currents are needed to reduce power consumption and heat dissipation while stability of the fundamental transverse mode is essentially to avoid nonlinearities in the P(I)-characteristics of the lasers. In the past, several laser structures have been developed to meet these requirements /1,2,3/. However, preparation of these devices becomes rather complicated by processing steps like oxide isolation, diffusion or double-epitaxy. It is the purpose of this paper to describe the mechanisms of current confinement and transverse mode stabilization of a newly developed simple laser structure /4/. Furthermore, detailed measurements on the relevant lasing characteristics are presented.
Fabrications and Single Transverse Mode Operations of GaInAsP/InP Terraced Substrate Lasers
Authors: Moriki K. , Wakao K. , Kitamura M. , Iga K.
Published: February 2023

GaInAsP/InP DH lasers operating at the controlled and stabilized modes are very attractive for fiber communications. For this purpose, various kinds of lasers with built-in index guide are reported.1-8)
Whispering Gallery Lasers on Semi-Insulating GaAs Substrates
Authors: Ury I. , Margalit S. , Bar-Chaim N. , Yust M. , Wilt D. , Yariv A.
Published: February 2023

Recently, integrated optical circuits consisting of optical detectors, active electronic devices, and injection lasers have been fabricated on semi-insulating GaAs substrates.1,2,3 A severe limit however is placed on the maximum allowable chip size if the lasers are formed between parallel cleaved facets. This problem can be alleviated if the light in the laser cavity is made to follow a semi-circular path to a single mirror facet or to follow along a quarter circle at a cleaved corner. In our implementation, the optical mode in the laser cavity is guided by total internal reflection along a single curved dielectric interface in the manner of the whispering gallery.4 Whispering gallery injection lasers have been previously fabricated,5 but only on conductive substrates.
Optical Bloch waves in periodic planar waveguides
Authors: Ulrich R. , Zengerle R.
Published: February 2023

The elementary solutions of the wave equation in a periodic waveguide (Fig. 1) are waves of the Floquet-Bloch type.1,2 They are formed by the superposition of a set of plane waves, called space harmonics (SHs). An equivalent description is possible3 by the coupled mode formalism, considering plane waves (the SHs) as the elementary excitations which are coupled by the structure of the guide. For a discussion of wave propagation over extended areas of periodic guides we adopt here the Bloch viewpoint. Below, we summarize briefly the properties of optical Bloch waves of general direction

s
→

of propagation. We show their direct excitation by a prism coupler, permitting a measurement of the complete dispersion characteristic

ω

β
→

of the guide. We then discuss transitions between periodic and nonperiodic guides, showing the unusual optical effect of negative refraction.
Fiber Optic Sensors
Authors: Giallorenzi T. G. , Burns W. K. , Donovan J.
Published: February 2023

Fiber optic sensors appear to offer significant performance advantages when compared to conventional acoustic, magnetic, and rotation sensors. This paper will review the state of the art in this newly developing technology area.
Electrooptic Polarization Modulated Injection Laser
Authors: Reinhart F. K. , Logan R. A.
Published: February 2023

We describe a novel class of semiconductor lasers made possible by monolithic optical integration. Depending on the operating parameters these integrated lasers can be operated in various operational modes: i) polarization modulation, ii) frequency modulation, or iii) astable mode (controlled Q switching). These devices consist of an optical amplifier (A) taper coupled to a polarization modulator (M) and a polarizer (P). We have observed equivalent polarization rotation of 40° with only 6V applied bias change, ΔVm, to the modulator section. We have also found strong frequency (or wavelength, λ) modulation with wavelength shifts as large as 20 Å with ΔVm ≈ 1V.
An Integrated-Optics Sub-Picosecond Gate
Authors: Marcatili E. A. J.
Published: February 2023

This paper describes a novel gate that opens and closes in less than 0.1 psec and that may be built with present-day integrated optics technology. For reasons that will become evident later we propose to call this device a velocity-matched gate (VMG).
A Very High Throughput Damage-Resistant Lithium Niobate Waveguide Modulator
Authors: Holman R. L. , Cressman P. J.
Published: February 2023

The use of electrooptic diffraction in a lithium niobate waveguide to deflect a laser beam efficiently, and at high speed, in response to a relatively low voltage, has been well established [1-2]. Practical applications, on the other hand, have been discouraged by the historical shortcoming of the lithium niobate: its susceptibility to laser damage. Moreover, it has proven difficult to couple a laser into, and out of, the lithium niobate waveguides, efficiently and reproducibly. Recently, we reported a chemical process for forming low-loss lithium niobate waveguides that resist optical damage, even at very high laser powers, and short laser wavelengths [3]. More recently, we developed an improved tapered-gap prism coupler, and optimized it for very efficient coupling (>80%) to our single TE mode, damage resistant lithium niobate waveguides [4-6].
Reactive ION Etching of III-V Compounds
Authors: Howard R.E. , Hu E.L. , Coldren L.A.
Published: February 2023

Reactive ion etching (RIE) has been used to transfer high resolution sub-micron patterns into Si, SiO2, and Si3N4 substrates. One example of this is the patterning of square wave gratings 250Å deep with 3200Å periodicity into SiO2(1). The utility of this technique for the fabrication of component devices for integrated optics is manifest. We report the first successful application of this technique to GaAs, InP and In.83Ga.17As.37P.63. All edges of the etched structures are sharply defined, the smoothness of the walls are at present limited only by the quality of the masking. The floors of the substrate are largely flat and featureless.
Fabrication of Submicrometer Period Gratings with Precisely Defined Profiles for Integrated Optics Applications*
Authors: Flanders D. C. , Hawryluk A. M.
Published: February 2023

Several integrated optics devices require precisely defined gratings with submicrometer periodicities. These include distributed feedback lasers, filters, resonators, input-output couplers, etc. Two recently developed techniques [1,2] for fabricating grating structures will be described together with the application of these techniques in the field of integrated optics.