bluuebunny/crossref_metadata_2025 huggingface dataset:
Global Communication, Accuracy and Optical Threshold Device Tolerances in Digital Optical Matrix Multipliers
Authors: Wagner Kelvin , Weverka Robert T. , Psaltis Demetri
Published: February 2023

Analog optical array processors are limited in dynamic range and accuracy to about 1000:1. To circumvent this limitation residue, binary, or other radix encoding schemes can be employed. Invariably, nonlinear logical operations must be performed on the input data streams in order to perform operations such as additions and multiplications on the encoded data samples. The standard approach used in electronic systems is to perform pairwise locally connected bit operations sequentially in a tree or array configuration of adder or multiplier primitives, each formed out of boolean switching devices. This approach is dictated because of the local wiring constraints inherent to planar technologies, and the availibility of only low dimensionality switching primitives (i.e. logic circuits which have very few inputs).
Optical Nonlinearities of Glasses Doped with CdSxSe1−x
Authors: Peyghambarian N. , Olbright G. R.
Published: February 2023

Glasses doped with CdSxSe1−x microcrystallites, which are normally referred to as color filters, display interesting properties. Jain and Lind1 reported degenerate four-wave mixing experiments in these samples and observed 8-ns-pulse-width limited-decay time for the grating. Thomazeau et al.2 used the optical Kerr effect to measure and time resolve the nonlinearity of lead-silicate glasses on a femtosecond time scale. They measured less than 100-fs response time for the nonlinearity. Yao et al.3 used pulses of 30-ps duration, and reported free-carrier lifetimes of a few tens of picoseconds. Gibbs et al.4 observed increasing absorption optical bistability and longitudinal excitation discontinuity in these filters arising from thermal nonlinearity. However, the origin of the optical nonlinearity originating from the electronic processes has not yet been studied carefully in these glasses. In this paper, the results of a pump-probe experiment are reported, and it is concluded that the nonlinearity arises from a bandfilling effect.
Pulse Shaping in CuCl due to Nonlinear Dispersion and Absorption
Authors: Bigot J.Y. , Frindi M. , Hönerlage B. , Levy R. , Grun J.B.
Published: February 2023

We report experiments on CuCl at 2 K with temporal, spectral and spatial resolution. The samples used are either vapor phase grown platelets or polycristalline films deposed on silicon substrates. They are excited by a nanosecond pulsed dye laser whose transmission is analysed temporally using a streak camera with picosecond resolution. The photon energy of the laser is varied around half the biexciton energy [1]. The spatial resolution is achieved using films of 2,7, 10 and 13 μm and platelets of about 30 μm thicknesses. We are thus able to study the nonlinear propagation of pulses for different wavelengths and intensities, through samples of different thicknesses.
Bulk ZnSe: Linear Transmission to Damage Through Dispersive Bistability and Absorptive Switching
Authors: Kar A.K. , Wherrett B.S.
Published: February 2023

Optical bistability and switching can be obtained in a number of semiconductors in various ways: dispersive bistability of electronic origin(1,2), thermal dispersive bistability(3,4) and absorptive switching(5,6).
Simultaneous Optical Bistable Switching of Adjacent Pixels on a Uniform ZnS Interference Filter
Authors: Jin R. , Wang L. , Sprague R. W. , Olbright G. R. , Kulcke H. , Gigioli G. C. , Gibbs H. M. , Macleod H. A. , Peyghambarian N.
Published: February 2023

The characteristics of thin-film interference filters are being studied because of their potential use for parallel processing and digital optical computing.1 Two-dimensional arrays of a large number of pixels have been envisioned to operate simultaneously in a parallel processing device.2 Optical combinatorial logic, processor-to-processor communications, and crossbar interconnection are only a few of the possible parallel operations that can be addressed by a two-dimensional pixel array. Previously, Karpushko and Sinitsyn,3 and more recently, Weinberger,4 Olbright,5 and Smith6 have developed interference filters using ZnS and ZnSe, which exhibit room-temperature optical bistability with visible light. ZnS (375-nm band edge) is chosen here for operation at 514.5 nm where large lasers with cw power in excess of 10 watts is available, thus facilitating the potential for large array processing.
Control of the Spatial Intensity Distribution of a σ+ Beam by a σ− Beam
Authors: McCord A.W. , Ballagh R.J.
Published: February 2023

Beam reshaping effects which occur in propagation through a non-linear medium1 are very sensitive to the form of the radiation-matter interaction. A second beam may alter the medium response for the original beam, leading to a dramatic change in its spatial intensity profile.
Dual-Phase Oscillation from CW Transverse Instabilities in Sodium Vapor
Authors: Derstine M. W. , Gibbs H. M. , Hopf F. A. , Valley J. F.
Published: February 2023

Recent experiments1 on transverse instabilities in Gaussian laser beams using sodium vapor for the nonlinear medium have shown well-behaved oscillations of the type first proposed by Ikeda.2 The period of such oscillations for a medium with infinitely fast response is given by 2τr, where τR is the time it takes for light to traverse the feedback loop. Our experimental arrangement (Fig. 1) uses a ring dye laser with well-defined transverse properties tuned to a frequency 2 to 10 GHz below the sodium D2 resonance. Operation on the self-defocusing side guarantees that no self-trapped filaments are formed. A feedback mirror several meters from the sodium sample provides the delay needed for the Ikeda instability.
Instabilities in a CO2Laser with Feedback on Intracavity E-O Modulator
Authors: Gadomski W. , Salieri P. , Arecchi F.T. , Meucci R.
Published: February 2023

In a homogeneously broadened CO2laser [1] only the polarization can be adiabatically eliminated (class B lasers), so that the dynamics is ruled by two rate equations for the field and population inversion (

I
=

E
2

/

E
s
2

is the field squared and normalized to saturation intensity

E
S
2

=

γ
⊥

γ

IL

4

g
2

 
,
G
=
2

g
2

/

γ
1

is the coupling factor, d is the population inversion normalized to the pump value Δo, with g = wµ2/ħϵoV and γ1, γILfor the polarization and population inversion decay rates).
Bistability by Reflection at the Boundary of a Saturable Absorber
Authors: Roso-Franco L.
Published: February 2023

Numerical analysis of the Maxwell—Bloch equations shows that the normal incidence reflection of a plane monochromatic wave at the boundary of an absorber built up by independent two-level systems at rest exhibits bistable behavior. The propagation equation is where F is the rescaled field amplitude at each point of the absorber and ψ is another dimensionless parameter that accounts for the strength of the coupling.
Optical Multistability in a Four-Level System Interacting with Two Fields
Authors: Kagan D. , Friedmann H.
Published: February 2023

We have studied the case of optical multistability in a four-level system interacting with two coherent fields. The system, shown in fig. 1, consists of two pairs of energy levels, 1, 2, and 3, 4, absorption occurs between levels 1- 4 and emission takes place from 3-2. The 'intra-band' transitions, 4-3 and 2- 1 are assumed non-radiative and extremely fast. The system is irradiated by two beams, one tuned to the absorption spectrum, the other to the emission spectrum, in a Fabry-Perot cavity. Solution of the optical Bloch equations following [1] enables us to write the input-output equations, la and lb, in the form where Yi, Xi, are the appropriately scaled input and output fields, Ci the 'bistability' parameter, and Δi, ϕi, the atomic and cavity detuning respectively, of field i.
Cross-Trapping Optical Bistability of Two Counter-Propagating Beams in Sodium Vapor
Authors: Mysyrowicz A. , Tai K. , Gibbs H. M. , Peyghambarian N.
Published: February 2023

The interaction of two counterpropagating beams in a nonlinear medium leads to many interesting phenomena. One such phenomenon is the occurrence of optical bistability arising from the mutual interaction of the two beams.1 This type of cross-trapping optical bistability is similar to one of those proposed by Kaplan.2 The physics of cross-trapping optical bistability is similar to the self-focusing bistability3 where self-trapping occurs in a single-beam/single-reflector setup. Cross-trapping bistability differs in that it has no external feedback and therefore is the first mirrorless bistability not based on an increasing absorption effect.
Liquid Crystals as Nonlinear Optical Materials
Authors: Shen Y. R.
Published: February 2023

Liquid crystals are highly nonlinear materials. Typical liquid crystal molecules possess a strong second-order nonlinear polarizability. The overall medium could have a large second-order nonlinearity if the molecules could be aligned with a polarity. This is unfortunately not the case in practice without special treatment to the sample. The possibility that liquid crystal polymers can be efficient second-order nonlinear optical media is certainly very attractive.
Optical Circuitry Cooperative (OCC)
Authors: Gibbs Hyatt M.
Published: February 2023

Optical circuitry is an emerging technology that has the potential for making major, if not revolutionary, contributions to signal processing, communications, and computing.
Theory of Transient Optical Bimodality
Authors: Broggi G. , Lugiato L. A. , Colombo A.
Published: February 2023

From a statistical viewpoint, the signature of optical bistability is the two-peaked character of its stationary probability distribution. However, the exceedingly long lifetime of the two metastable states makes the experimental observation very difficult. We recently showed (1) that the critical slowing down can produce the emergence of a double-peaked distribution during the transient, with a scenario that is accessible to experimental observation, a goal that has been brilliantly achieved by the Hannover group (2) using optically pumped sodium vapour. This phenomenon, called transient bimodality, is universal in the sense that it arises in all systems that, at a deterministic level, exhibit a long induction stage followed by a fast switching to the steady state (3). And, in fact, the Hannover team observed this phenomenon also in an electronic system (4).
Experimental studies of fluctuations in transient optical bistability
Authors: Lange W. , Deserno R. , Mitschke F. , Mlynek J.
Published: February 2023

Experiments on the dynamics of bistable switching in the presence of external noise are performed by means of a sodium-filled Fabry-Perot resonator. Its response to a sudden switch-on of a resonant laser beam is monitored /1, 2/.
Quantum Statistics of Small Bistable Systems
Authors: Carmichael H. J.
Published: February 2023

The quantum statistics of bistable systems have been studied since the beginnings of optical bistability theory. Predicted quantum-statistical effects include quantum induced transitions between states, evidences of atomic collectivity in the transmitted spectrum, photon antibunching, and squeezing.(1) The enthusiasm shown in theoretical analyses of these phenomena has not been matched by experiments, however; one reason being that the effects are very small, generally scaling with the size of the system (in this squeezing is an exception) as measured by saturation photon number nS or number of atoms N. The recent experiments of Rosenberger et al.,(2) which closely meet the idealized conditions called for by theory have ns ~ 103 and N ~ 105. While these numbers are too large, these experiments suggest that it might be feasible to measure quantum-statistical effects in a new generation of smaller systems. This paper addresses theoretical questions raised by a move to small systems. Existing theories are themselves restricted by assumptions of large system size, invoked to justify their various truncation, factorization and linearization procedures.
Application of the Non-Linear Eikonal Treatment to the Design of Optical Bistable Devices
Authors: Orenstein Meir , Speiser Shammai , Katriel Jacob
Published: February 2023

Recently we have developed [1,2] the non-1inear-complex-eikonal approximation. Our goal was to set a standard mathematical treatment for the analysis of the propagation of light waves through non-linear media. The linear eikonal approximation is a cornerstone for optical systems design and we hope that the non-linear eikonal method will gain some of the universality of its linear counterpart.
Light - Induced - Desorption: A New Mechanism for Bistability In Integrated Optical Devices
Authors: Lukosz W. , Briguet V.
Published: February 2023

We have demonstrated a new mechanism for bistability in integrated optics, viz., light-induced-desorption of molecules from the waveguide surface by which the effective guide index N is changed. Bistability occurs if the desorption rate depends linearly on the incoupled power P' in an input coupler device (see Fig.1), and on the intracavity power in an IO Fabry Perot or ring resonator. This follows theoretically from an analysis analogous to that of the bistable radiation pressure driven waveguide pendulum.1
Optical Bistability in 1.55 μm Semiconductor Laser Amplifiers
Authors: Adams M J , Westlake H J , O'Mahony M J
Published: February 2023

Dispersive bistability arising from the carrier-dependence of the refractive index has been observed in semiconductor lasers operated just below threshold with a small injected optical signal. The minimum optical input required for switch-up is as low as 1 μW for InGaAsP amplifiers at 1.55 μm(1) and 1.3 μm(2) (cf 30 μW for GaAs devices(3)). As yet, reliable measurements of the dynamic response are not (4) available, although we predict recovery times to be on the order of carrier lifetimes, ie a few nanoseconds at room temperature. This contribution will review our experimental and theoretical work on 1.55 μm amplifier bistability and set it in the context of other semiconductor bistable optical devices.
Femtojoule Switching in Nonlinear Semiconductor Laser Amplifiers
Authors: Sharfin Wayne , Dagenais Mario
Published: February 2023

We have observed fast optical switching in an InGaAsP/InP Fabry-Perot optical amplifier with as low as one microwatt of optical input power.1 Detector-limited switching times of about 3 ns are observed, indicating actual times of less than a nanosecond (Fig. 1). The switching energy of one femtojoule corresponds to less than 7000 input photons at 1.3 μm wavelength. For a 5 Ohm device with a typical threshold current of 20 mA and a switching time of a nanosecond, 20 pJ of electrical energy is expended to switch the device. The extremely low optical switching energy of these devices suggests the potential for extremely high data throughput using two-dimensional arrays of similar devices for parallel processing. The optical switching energies of these devices are more than three orders of magnitude lower than any previously reported. Moreover, gain in these amplifiers offers the important potential for cascadability.
Subharmonic Phase Memory: Symmetric Optical Multistability
Authors: Kaplan A.E.
Published: February 2023

It is well known that n-th order subharmonic oscillations (where n is integer) possess a fundamental property of having n possible and equally probable oscillation phases, each of which corresponding to the same oscillation amplitude.1 It was demonstrated both theoretically and experimentally by this author2 that very high order subharmonics can be excited in passive lump nonlinear systems driven by a sufficiently strong pumping signal. It was also shown that subharmonics can be generated by the optical parametric oscillator.3 In this paper we show that optical subharmonic oscillators may provide a novel kind of optical multistability - specifically, phase multistability of these oscillations, with the same amplitude for each steady state of the phase. This differs drastically from all presently known types of optical bistability, all of which are based on amplitude multistability. The new principle results in a unique property of the system which we call symmetry of the states: all the steady states of the system possess the same stability, noise, etc. characteristics and may be switched from one steady state to another by an external signal of the same small amplitude.
Instabilities in dispersive OB on the low transmission branch
Authors: Erneux T. , Mandel Paul
Published: February 2023

We study the mean field limit equations for optical bistability using two-level atoms as a model for the nonlinear medium. The resulting standard equations are /1/: The steady state equation is.
Frequency Locking, Intermittency, and Chaos in Semiconductor Lasers
Authors: Chen Y. C. , Winful H. G.
Published: February 2023

A semiconductor laser whose cavity contains a saturable absorber can exhibit a wide variety of instabilities including self-sustained pulsations of the output radiation for a constant driving current. We have investigated the nonlinear dynamics of a self-oscillatory semiconductor laser whose pumping current is modulated at a frequency fm close to the free oscillation frequency f0 or one of its harmonics. As the modulation depth is increased we observe frequency locking, intermittency, and chaotic behavior in the output radiation. Our observations agree well with numerical simulations based on the rate equations for a laser with a fast saturable absorber.
Optical Bistability due to mode-mode competition in a CO2 laser
Authors: Narducci L. M. , Tredicce J. R. , Abraham N. B. , Bandy D. K.
Published: February 2023

Homogeneously broadened lasers are considered as intrinsically single mode monostable devices [1] where intensity and frequency are defined by the cavity mode that lies nearest to the center of the atomic line. Here we show theoretically and experimentally that this heuristic picture falls when the interaction between different cavity modes becomes relevant. In fact, for sufficiently high detuning between cavity and atomic resonance frequencies (δAC), self pulsing of the laser arise from the simultaneous operation in two modes (phase instability) even if it is operating near threshold (C ⪯ 1) and in the so-called good cavity limit (k ≪ γ⊥, γ‖). Using parameter values which are typical of many solid state and molecular gas lasers (γ‖, k ≪ γ⊥), the theory predicts a bistable behavior in both the output intensity and frequency, as δAC is varied (Fig. 1). These theoretical results have been confirmed by experiments carried out on a CO2 laser where the distance between modes was controlled by changing the losses inside the cavity and the detuning δAC was varied by a fine tuning of the distance between mirrors. The output intensity versus δAC is shown in Fig. 2 for two different values of losses and gas pressure. Direct comparison between Fig. 2b) and Fig. 1 shows a good qualitative agreement. Measurements of the transients during the jump of Fig.2b) confirmed the mode-mode competition interpretation.
Instabilities in the Propagation of Arbitrarily Polarized Counterpropagating Waves in A Kerr Medium
Authors: Gaeta Alexander L. , Boyd Robert W. , Milonnl Peter W. , Ackerhalt Jay R.
Published: February 2023

There has recently been great interest in the instabilities that can occur in the interaction of two laser beams in a nonlinear medium. Silberberg and Bar-Joseph1 have predicted the existence of instabilities in the propagation of two scalar waves for the case of a Kerr medium characterized by a nonzero response time. Marburger and Lam,2 Kaplan and Law,3 and Lytel4 have shown that multistability can occur in the transmission of two counterpropagating vector fields in a medium with an infinitely fast response. In this paper, we show theoretically that instabilities occur in the polarization characteristics of counterpropagating vector fields for an infinitely fast Kerr medium. Our treatment includes the time evolution of the transmitted optical fields; previous workers2–4 have concentrated on the steady-state response.
Stability and Instability of Nonlinear Waveguide Modes
Authors: Jones C.K.R.T. , Moloney J.V.
Published: February 2023

A new class of nonlinear surface and bulk polariton modes have recently been identified in geometries in which one or more of the layered structures shows a nonlinear response to the applied electromagnetic field. Recent advances in the growth of epitaxial layers and in thin film technology have led to an active experimental search for such nonlinear waves over the pasf year.1 These structures show potential device applications as optical limiters, for example. An important question from both a technological and fundamental point of view, which we will address, is whether these various nonlinear waveguide modes are stable to propagation.
Mirrorless Optical Bistability Due to Coherent Dipole-Dipole Interactions in a Spacially Distributed Collection of Two-level Systems
Authors: Ben-Aryeh Yacob , Bowden Charles M.
Published: February 2023

Atomic cooperative effects in mirrorless (intrinsic) optical bistability (MOB) have been treated, so far, either by assuming a small volume with dimensions smaller than a wavelength1,2, or by assuming a system with a small number of atoms3. In the present work we discuss MOB based upon cooperative effects among atoms in a system consisting of many two-level atoms, considering explicitly the spacial dependence of the coherent dipole-dipole interactions.
Coherence and Chaos in Passive Nonlinear Optical Systems
Authors: McLaughlin D.W. , Newell A.C. , Moloney J.V.
Published: February 2023

An appealing idea of modem dynamics is that the complicated and apparently stochastic time behavior of large and even infinite dimensional nonlinear systems is in fact a manifestation of a deterministic flow on a low dimensional chaotic attractor. If the system is indeed low dimensional, it is natural to ask whether one can identify the physical characteristics such as the spatial structure of those few active modes which dominate the dynamics. The key idea is that each of these structures is a natural asymptotic state that, by virtue of the various force balances in the governing equations, developes an identity which does not easily decay or disperse away. Instead they persist and experience temporal chaos of at least two distinct types - a mild ’’phase” or more violent "amplitude” turbulence. Integrable soliton equations provide systems with many of the same qualitative properties of their finite dimensional integrable counterparts; phase space is foliated by nested tori, etc. It is fairly natural, then, to imagine that the effects of external influences (forcing, damping, coupling to other systems) will be similar to the finite dimensional case, and that the perturbed phase space will consist of a mosaic of islands of integrability and areas of stochasticity.
Instability Condition and Frequency-Locking in Hybrid Optical bistability
Authors: Chen Li-xue , Li Chun-fei , Hong Jing
Published: February 2023

In the linear instability analysis of the difference-differential equation which describes the dynamic behaviors of optical bistability with delayed feedback, introducing degree of stability S, which is defined as the ratio between relative variations of input and output intensities(1), we find that for long delay time instability condition is S≥2 and possible oscillation periods are approximately

T
¯

=
2
 
T
/
(
2
n
+
1
)

but for short delay time the condition is S≥1 + πτ/2T and the periods are

T
¯

=
4
T
/
(
4
n
+
1
)

. So the generation of instability for long delay time is easier than for short one, as shown in Fig.1.
Heuristic Model for Fluctuations in Mirrorless Optical Bistability
Authors: Hopf F.A. , Bowden C.M.
Published: February 2023

Recent interest has focussed on the subject of mirrorless optical bistability, the simplest system showing bistability theoretically is a system of N ≥ 2 atoms. Microscopic theory is derived from quantum theory by a factorization of binary products of operators. There are strong inter atomic interactions in the bistable regime, it is unlikely that these factorizations are valid. Quantum calculations that avoid factorization imply that bistability does not exist. Hence in the previous bistability conference there was skepticism that bistability could really occur in a mirrorless system with only a few atoms.
Quantum Dots and Wells with Enhanced Optical Nonlinearity and Fast Response
Authors: Hanamura Eiichi
Published: February 2023

Exciton, which is a coherent superposition of constituent atoms, has a macroscopic transition dipole moment and a large oscillator strength. The exciton, however, behaves almost as a harmonic oscillator so that it cannot contribute in itself to the nonlinear response. Therefore we propose two new functionality materials with large optical nonlinearity by making the exciton deviate very much from harmonic oscillator and at the same time making use of the large oscillator strength of the exciton.
The Geometrical Dependence of Transient Optical Nonlinearities in Multiple Quantum Well Structures
Authors: Manning R J , Crust D W , Miller A , Woodbridge K
Published: February 2023

Semiconductor multiple quantum well structures exhibit very large, room temperature, nonlinear refractive effects associated with resolvable excitonic features [1]. These nonlinearities may find use in all-optical devices if sufficient refractive index change can be achieved before the exciton completely saturates [2]. A unique aspect of band gap resonant optical, nonlinearities in quantum wells is the spatial confinement of the generated carriers within the layers. We have exploited the excitonic refractive nonlinearity in GaAs/AlGaAs multiple quantum wells in two separate degenerate four wave mixing configurations. These compare the intra-well and cross-well contributions to highly anisotropic carrier diffusion and also allow measurement of carrier relaxation rates and the saturation of the excitonic nonlinear refraction with increasing intensity.
Non-linear optical waveguiding in semiconductors
Authors: Lambkin P. , Shore K.A.
Published: February 2023

Practical device implementations of non-linear waveguides may utilise the defocussing non-linearity associated with the fundamental absorption edge of semiconductors. A suitable slab waveguide structure would involve a non-linear guiding layer bounded by cladding layers which are non-absorbing and hence linear at the operating wavelength. An analysis of TE modes in such a structure is given for the first time in this paper.
Model of a Nonlinear Guided-Wave Mach-Zehnder Interferometer in GaAs
Authors: Sarid Dror , Gibbons Wayne M.
Published: February 2023

The response of an all-optical nonlinear waveguide Mach-Zehnder interferometer (NLMZ) is analyzed using perturbation theory. The theory provides differential equations that describe the amplitude of the waveguide modes as a function of the propagation distance. To become practical, the waveguide device require nonlinear phase shifts of π or more. Therefore, the theoretical investigation of the device emphasizes its fabrication in bulk galium arsenide (GaAs). For the first time, absorption, carrier diffusion, and thermal effects are included in the theoretical investigation of the NLMZ. The effect of carrier diffusion on the nonlinear response of a GaAs waveguide is demonstrated using a self-consistent numerical method. The effect is heavily dependent on the waveguide geometry, and, therefore, should be included in the analysis of nonlinear semiconductor waveguide devices. However, if the diffusion length is large compared to the mode width, carrier diffusion simplifies the investigation since the nonlinear absorption and index change are uniform across the mode. This assumption is used in the modelling of the NLMZ, which predicts that the device should work in bulk GaAs.
Optical Stark Effect in GaAs Multiquantum Wells
Authors: Mysyrowicz A. , Hulin D.
Published: February 2023

Irradiation of a medium with non-resonant light leads to a shift of the energy levels in the system. This optical, or dynamical Stark effect has been studied for many years in atomic gases. It is only recently, however, that it could be detected for excitonic transitions in solids. This development has stirred considerable interest, because the optical Stark effect has inherent features which makes it well suited for applications such as in ultrafast all-optical data processing. Since the pump light beam falls in a transparency region of the medium, it experiences little loss, in contrast to optical non-linearities based on a saturation mechanism. Also, because virtual transitions are involved, the light-induced shift of exciton levels follows closely the pump pulse duration, making it possible to design ultrafast all-optical logic gates with subpicosecond switch-on and -off times.
Optical Cellular Automata : Architectural Principles
Authors: Chavel Pierre , Taboury Jean , Devos Francis , Garda Patrick
Published: February 2023

Clearly, one issue faced by emerging optical computing technology is the effective combination of parallelism with short cycle time in parallel processor arrays. In particular two-dimensional arrays of bistable or otherwise non linear elements may be interconnected by dense three-dimensional light beams into cellular processors.
N-Type Differential Negative Resistance, Optical Bystability and Automodulation of Radiation in Semiconductors Due to Electrooptical Effects
Authors: Ryvkin B.S.
Published: February 2023

There are many physical mechanisms which give rise to N-type current-voltage characteristic (CVC) in semiconductors. Of special interest is the possibility of obtaining N-type CVC for photocurrent of semiconductor photosensitive element due to the reduction in the absorbed light power (P) when the applied voltage (V) is increased. On the basis of such electrooptical elements it was possible to fabricate devices (SEED) for optical radiation control. The principle of obtaining N-type CVC in the SEED can be explained in the following way. In any photoelectric devices photocurrent is defined by the concentration of carriers n created by light. This concentration is proportional to product: n~∝P, where ∝ - is absorption coefficient of the SEED material. N-type CVC may take place if any of the values ∝ or P decrease when V grows. In-crease of V (i.e. electric field E inside the SEED) can alter the refraction index or/and the absorption coefficient of the SEED material. The change in the refraction index may produce essential change in concentration n if the SEED is made like a Fabry-Perot resonator (FPR). In this case continuous increase or decrease of the refaction index with E causes continuous change in the optical length of the FPR and, consequently, oscillations of P inside the SEED. The reduction of P in this case gives rise to N-type CVC [1-3]. For the photon energy ħω close to the energy gap Eg of the semiconductor the increasing of E results in the increase of ∝ , if ħω<Eg, and may result in decrease of ∝ , if ħω slightly exceeds Eg. The growth of ∝ with E in the active layer of the resonator SEED can result in the reduction of n , i.e. N-type CVC. This may occur because in the resonance region the increase in ∝ results in a drastic drop in the P inside the FPR, so that in the product this reduction overcompensates the rise of the ∝ [2,3]. On the other hand, reduction of ∝ with E in the narrow gap i-type layer of the SEED made on the basis of the double P - i - N heterostructure enables us to obtain N-type CVC in a simple and elegant way [3-5]. In the latter case the SEED has no resonator and nonmonochromatic radiation can be used.
Transverse Effects in Optical Bistability
Authors: Rosanov N. N.
Published: February 2023

Summary not available
Transverse Traveling Pulses in Bistable Interferometers with Competing Nonlinearities
Authors: Rzhanov Yu.A. , Grigor’yants A.V. , Balkarei Yu.I. , Elinson M.I.
Published: February 2023

We have numerically investigated the dynamics of initiation and propagation of traveling pulses (TP) in the semiconductor interferometer with two competing mechanisms of nonlinear refraction, connected with interband free carriers photogeneration and semiconductor heating. The possibility of existence of TP, which represent the novel type of transverse effects in optical bistability, have been predicted in our recent work /1/. TP are realized under pumping intensity close to the threshold of originating of McCall’s type regenerative oscillations (RO) /1,2/, when interferometer responds to a weak additional signal by single optical pulse with standard shape (regime of single-shot multivibrator /1,3/ ). If transverse dimentions of the interferometer are large enough, then under constant plane-wave pumping and additional local lighting the optical- carrier density TP arises. TP has sharp forward and backward fronts and moves across pumping beam with constant velocity due to carrier diffusion. After the passage of traveling pulse the system returns back to initial homogeneous steady state. Changing parameters of the interferometer or pumping intensity, we can obtain TP with increased or decreased transmission (direct or inverted TP), each of them can be initiated by lokal increasing or decreasing of input intensity. If interferometer is pumped by beam with Gaussian profile, the thentral - intensive part of the beam can corresponds to RO while the beam periphery- to the single--shot regime. In this case the central part of the beam serves as a periodic source of TP, moving towards beam periphery. The contraversal situation is possible, when the periphery of Gaussian beam corresponds to the RO, while the central part - to the single-shot regime. In this case TP are periodically spontaneously initiated at the beam periphery and move to the beam center. Two TP annihilate after collision. In the both cases profile of transmitted beam periodically changes. All regimes described above have been found by numerical simulation using interferometer parameters close to InSb /4/.
Pixellation of Optothermal Bistable Devices for Switch Power and Cross-Talk Reduction
Authors: Kar A.K. , Harris R. , Buller G.S. , Smith S.D. , Walker A.C.
Published: February 2023

The etching or machining of grooves so as to delineate isolated areas on a nonlinear interference filters (NLIFs) inhibits transverse conduction and consequently reduced both cross-talk effects and switch powers for optically bistable arrays. Assuming one-dimensional heat-flow through an insulating layer, into a high thermal conductivity substrate, switch energies in ZnSe NLIFs of around 10 pJ μm-2 are predicted [1,2]. The insulating layer between the NLIF and the heat-sink, which is to be pixellated, must be a non-crystalline material, for low thermal conductivity. Consequently direct etching, to form deep, narrow grooves, cannot be achieved with chemical etching techniques. Instead, we have used a laser micro-machining technique to process glass substrates, both before and after deposition of the multilayer device.
Modelling of Cross Talk in 2D Bistable Arrays and Noise on an InSb Etalon
Authors: Abraham E. , Richardson H.J.
Published: February 2023

We consider an InSb etalon illuminated by N Gaussian beams forming a 2D array. As the refractive nonlinearity is electronic, the photo-excited carriers diffuse and coupling between elements occurs.
All-Optical Digital Circuits
Authors: Tooley F.A.P. , Wherrett B.S. , Craft N.C. , Taghizadeh M.R. , Snowdon J.F. , Smith S.D.
Published: February 2023

Absorbing interference filters can be used as optical three-port logic gates exhibiting gain, hard-limiting single wavelength operation [1]. Furthermore, their large-area (~ cm2) uniformity ensures that two-dimensional arrays of gates (~ 100) can be operated independently with similar power transfer characteristics (a variation of a few percent in the switching power). Such devices offer the potential to demonstrate the feasibility of novel digital computing techniques. The presentation will describe the successful operation of two looped optical circuits; a 4-channel flip-flop and a circuit which demonstrates that a full-adder can be constructed by using the reflected and transmitted outputs from a single gate simultaneously and that these outputs are cascadable, Figure 1 [2]. In addition, the operation of a pipelined circuit which performs digital edge extraction will be described with emphasis on the role of holographic interconnection (multiple fan-in and fan-out) of arrays of logic gates, Figure 2. The successful operation of such circuits places constraints on the individual responses. These will be analysed using a recently developed operating curve technique.
Non Critical Slowing Down in Optical Bistability
Authors: Segard Bernard , Macke Bruno
Published: February 2023

We report on the switching dynamics of a bistable device in the case when a holding power maintains the system in a stable state of the lower branch and a pulse address of finite duration (T) brings it close to the unstable state of the middle branch. For a critical pulse duration (Tc) the pulse exactly brings the device in the unstable state where it would indefinitely remain in the absence of fluctuations. For pulse duration close to Tc the device switches up to the upper branch (T>Tc) or relaxes to the initial state (T<Tc) after a lethargy time which follows a logarithmic law {1,2}.
The Dynamic Response and Noise Susceptibility of c.w. Bistable Systems
Authors: MacKenzie H.A. , Young J. , Iltaif A. , Hughes J.
Published: February 2023

The dynamic response of a bistable system may be analysed via a Debye
equation of the form [1] and, if the system is
perturbed at a particular phase ϕs, the time
response is characterised by an effective time constant
τe given by This time constant determines the
dynamic frequency limits which are applicable through the bistable
switching process and as the switch points are approached there is a
dramatic increase in τe and a corresponding
reduction in the frequency to which the system can respond.
Optically bistable reflection from a nonlinear multilayer : an exact theory
Authors: Boardman A.D. , Wilkins M.
Published: February 2023

Recently1, an exact theory of the irradiated nonlinear Fabry-Perot cavity and the ensuing multistability has been published. In this paper this approach is developed further and an exact treatment for the reflectivity and transmissivity of an optically isotropic structure of dielectric layers characterised by a third-order polarisation tensor at arbitrary angles of incidence is presented. The calculations use exact2 solutions of the nonlinear wave equation, rather than the commonly used ray treatment. This takes into account fully the standing wave effect and permits a precise examination of the interaction between the forward and backward travelling waves and the relationship between the transmissivity resonance condition and changes in the field profile. For an s-polarised incident wave an analytical solution is found for arbitrary angles of incidence and layer thicknesses. It is discovered that for certain ranges of layer thickness the system displays a multivalued response only above a critical angle. This bistability is achieved for irradiances much lower than those reported previously1 for normal incidence and indicates possible applications for optical processing. This plane wave treatment is supplemented by a numerical beam simulation which goes beyond the usual Fresnel approximation by utilising novel boundary conditions which permit the demostration of bistability.
Theory of the Nonlinear Optical Response of Active Multilayer Interference Filters
Authors: Hutchings D.C. , Wherrett B.S. , Frank D.
Published: February 2023

Intrinsic refractive optical bistability has now been observed in many semiconductors [1]. Switching power levels in such systems are typically in the range 1-100 milliwatts. Having in mind arrays of bistable elements for two dimensional optical information processing it will be necessary to achieve 1-100 microwatt switching power levels in order to realise the parallelism that optics offers at moderate total power levels.
Optical Bistability in a Laser with a Saturable Absorber: Theoretical Modelling and Transient Response in the Presence of Noise
Authors: Arimondo E. , De Tomasi F. , Fronzoni L. , Hennequin D. , Papoff F. , Zambon B.
Published: February 2023

Optical bistability in an infrared laser containing an intracavity saturable absorber (LSA) has been investigated in the static regime as a function of the control parameter governing the laser amplifier and absorber operations. Furthermore the switching dynamics between the bistable states has been studied in the critical slowing down regime when external noise was applied to the control parameter of either the amplifier or the absorber.
Polarisation Switching and Submilliwatt Laser Diode Induced Bistability in Nematic Liquid Crystals
Authors: Lloyd A.D. , Wherrett B.S.
Published: February 2023

For highly parallel digital optical processing, bistable devices operating in the 10-100 μW regime will be necessary.
Optical Bistability in Semiconductor Laser Amplifiers
Authors: Adams M J
Published: February 2023

It has recently become clear that OB in semiconductor laser amplifiers has many potential advantages for applications in optical logic and signal processing. Foremost among these advantages may be listed (i) ready availability (compared with other bistable devices [1]), (ii) wavelength compatibility with optical communications systems, (iii) inherent optical gain (for serial processing), and (iv) a combination of microwatt switching powers and nanosecond switching times leading to femtoule optical switching energies [2,3]. In support of item (ii) on this list, it is worth noting that amplifier OB has been reported at 0.8 μm [4], 1.3 μm [5], and 1.5 μm [6], all of which are wavelengths employed for optical communications systems.
Bistable Optical Solitons
Authors: Kaplan A. E.
Published: February 2023

We showed recently [1] that a single soliton solution of the highly-nonlinear Schrödinger equation becomes multi-stable for a certain class of nonlinearities. This implies that more than one amplitude profile and propagation constant of a single soliton may exist for the same total power carried by the soliton. The multistable solitons exist only if the nonlinear component of the susceptibility as a function of intensity is either changing its sign or its derivative has a sufficiently sharp peak. This can result in such effects as bistable (or multistable, in general) self-trapping of light in nonlinear media as well as bistable propagation of soliton pulses in nonlinear optical fibers. Both of these processes may be described by the same nonlinear Schrödinger equation with a nonlinear term in the form Ef(|E|2) where f(|E|2) is an arbitrary function of the field intensity |E|2 with f(0) = 0. The so called cubic nonlinear Schrödinger equation with f(|E|2) proportional |E|2, corresponds to Kerr-nonlinearity in optical propagation and does not give rise to bistable solitons). By evaluating the propagation constant of a solitary solution δ as a function of its total power P for each given f(|E|)2), we found a class of nonlinear functions f(I) for which the dependence δ(P) becomes multivalued. We conjectured earlier [1] that stable (unstable) solitary solutions are those with dδ/dP > 0 (dδ/dP < 0). The first computer results by Enns and Rangnekar [2] supported this conjecture for a certain non-Kerr nonlinearity. In our further collaborative research [3], we discovered that depending on the nonlinear function f(I), the stable solitary solutions (dδ/dP > 0) fall into two classes: “weak” solitons (stable only against sufficiently small perturbation), and “robust” solitons (stable against any perturbation, in particular, against collisions with other solitons). It was shown [3] that while the condition dδ/dP > 0 is sufficient for the “weak” stability, some extra conditions imposed on the function f(I) warrant existence of “robust” solitons (one of them e.g. is f(I)/I2 = o(1) as I → ∞; stability against collapsing behavior). It was shown most recently by Enns [4] that at least for some of the nonlinear functions of (|E|2) giving rise to bistable solitons, the nonlinear Schrödinger equation passes the so called Painleve test and is therefore completely integrable. This confirms that the “robust” solitary solutions are indeed solitons. The propagation of single pulses in nonlinear fibers with an appropriate nonlinearity may provide the first known opportunity to obtain a temporal (dynamic) bistability as contrasted to the known kinds of optical bistability which are so far based on the equilibrium regimes.
Optical Bistability with Rydberg Atoms
Authors: Lange W. , Schulz W. , Walther H.
Published: February 2023

Rydberg atoms are well known to have an extremely strong coupling to the electromagnetic field1,2, allowing experiments with only a few numbers of photons and atoms3. We use a 3-step excitation to pump rubidium atoms into the 62F level (Fig.1). The atoms traverse a superconducting niobium ring resonator, where they interact with a microwave field (Fig.2). Its frequency as well as the cavity may be tuned to resonance at 18.2 GHz with the 62F-64D transition, which yields a dipole moment of approx. 1570 eaO. Time-of-flight broadening of about 100 kHz leads to a saturation photon number of the order of 10.
Low-Power Optical Bistability and Phase Conjugation in Polydiacetylene
Authors: Blau W.
Published: February 2023

Thermally induced optical bistability is reported at 514 nm using a Fabry-Perot cavity filled with polydiacetylene. Simultaneous degenerate four-wave mixing shows corresponding bistable behaviour of the phase conjugate signal.
Electronic Optical Bistability in a GaAs/AlGaAs Strip-Loaded Waveguide
Authors: Gibbs H. M. , Warren M. , Gibbons W. , Komatsu K. , Sarid D. , Hendricks D. , Sugimoto M.
Published: February 2023

Previously reported work on optical waveguide bistability in GaAs/AlGaAs has included thermally induced dispersive and increasing-absorption bistability in a slab waveguide1 and increasing-absorption bistability utilizing the self-electro-optic effect in a slab waveguide.2 A more recent report claimed observation of optical switching and dispersive bistability of electronic origin in strain-induced channel waveguides.3 We report here an unambiguous observation of optical bistability of electronic origin in multiple-quantum-well (MQW) strip-loaded waveguides formed by reactive ion etching.
Switch Effect of Nonlclassical Ligth
Authors: Janszky J. , Sibilia C. , Bertolotti M. , Yushin Y.
Published: February 2023

We have studied the behavior of ligth with complex statistics (having squeezed, coherent and chaotic features) propagating inside a linear coupler. We show that the squeezed state can be switched from one channel to the other one, changing its squeezing properties, depending on the detuning parameter.
Modal Bistability in a GaAlAs Leaky Waveguide
Authors: Valera J.D. , Aitchison J.S. , Goodwill D.J. , Walker A.C. , Henning I.D. , Ritchie S.
Published: February 2023

Intrinsic optical bistability has been observed in a waveguide due to both optothermal [1] and optoelectronic [2,3] nonlinearities. In this paper we describe a bistable switching effect associated with mode distribution changes in a nonlinear leaky waveguide. The guide consisted of a Ga0.86Al0.14As layer, 3.6 μm thick and 200 μm, long bounded by GaAs and Ga0.9Al0.1As layers.