bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of Optical Bistability in Collinear Degenerate Four-Wave Mixing
Authors: Lytel Richard
Published: February 2023

Optical bistability occurs in many all-optical devices with non-linear couplings and feedback mechanisms. Thus, bistability is predicted for phase conjugate resonators,1 Fabry-Perot interferometers,2 and, generally wave mixing devices with a source of feedback. Bistability is therefore expected in four-wave mixing, where the Maxwell equations provide nonlinear feedback through the nonlinear susceptibility.
Optically-Induced Bistability in a Nematic Liquid Crystal
Authors: Ong Hiap Liew , Meyer Robert B.
Published: February 2023

Since 1979, considerable effort has been expended by many researchers in analyzing the purely optical-field-induced molecular reorientation in a homeotropically oriented nematic liquid crystal (NLC) by a normally incident light wave.1-4 Recently, the exact solution which is consistent with Maxwell's equations for describing the orientation of the molecule was obtained by Ong.5 In this paper, we shall discuss the exact solution describing the orientation of the director. In particular, by examining the deformation angle near the threshold, the criterion for the existence of a first-order Freedericksz transition is obtained.
Selfpulsings, Hysteresis and Chaos in a Standing Wave Laser
Authors: Kotomtseva L.A. , Loiko N.A. , Samson A.M.
Published: February 2023

Based on the system of semi-classical equations analysis and the numerical experiment, the temporal nature of the standing wave laser generation has been studied. It is shown that such a laser is a dynamic system in which, along with the selforganization processes leading to regular continuous pulsings /1/, stochastization of the strange attractor type is possible /2/. This diversified behaviour is due to the competition and interrelation of factors accounting for the steadystate behaviour instability. These factors are the development of nutation oscillations due to the coherent properties of the active medium and interaction of counterruning waves on the gain and losses inhomogeneities in the cavity differing in physical nature.
Room Temperature Optical Nonlinearities in GaAs Multiple Quantum Wells
Authors: Miller D. A. B. , Cnemla D. S. , Gossard A. C. , Smith P. W.
Published: February 2023

Progress towards practical all-optical switching and signal processing devices depends crucially on finding suitable nonlinear materials. Consequently, various workers have explored so-called 'dynamic' nonlinear optical effects in semiconductors(1) in which the optical properties change as a result of real excitation of the material. Semiconductors are particularly attractive for fabrication as small devices. Unfortunately, while some of these effects should persist to room temperature, one of the most attractive, saturation of free exciton resonances(2) is basically limited to low temperatures in conventional semiconductors because of thermal broadening.
Self-Pulsing, Breathing and Chaos in Optical Bistability and the Laser with Injected Signal
Authors: Lugiato L.A. , Narducci L.M.
Published: February 2023

The subject of spontaneous pulsations in Optical Bistability has stimulated considerable interest following its prediction by Bonifacio, and Lugiato1 in the framework of the plane-wave, ring cavity model and the realization by McCall2 of an electro-optical converter of cw coherent light into pulsed radiation. In a subsequent important development Ikeda3 showed that, in the dispersive case, the Bonifacio-Lugiato instability leads to chaotic behavior (optical turbulence). This was later observed in a hybrid device by Gibbs, et al4.
All-Optical Computation - circuit and component designs
Authors: Wherrett B.S.
Published: February 2023

The recent rise in interest in optical computation has been accompanied by a number of sophisticated proposals for optical processing elements, and a number of relatively abstract conceptual statements as to what the optical computer architecture of the future might look like.
Optical Bistability in PbSnSe at Room Temperature with Infrared Radiation at Milliwatt Powers
Authors: Kar A.K. , MacKenzie H.A. , Ji Wei , Reid J.J.E. , Grisar R. , Ball D. , Preier H.M.
Published: February 2023

Recently, thermally induced refractive index changes in semiconductors has been an area of growing interest [1,2]. In this paper we report the first observation of thermal optical bistability at room temperature in a bulk sample of PbSnSe (band gap 5.35 μm) using infrared radiation at 5.4 μm and at 10.6 μm. Bistable switching can be observed at a power level of less than three milliwatts at 5.4 μm as shown in figure 1. The results can be explained by thermal dispersive nonlinearity induced by a thermal shift of the band gap.
Pulsed Optical Logic in GaAs Etalons
Authors: Jewell J. L. , Lee Y. H.
Published: February 2023

Binary optical logic operations (NOR, etc.)1 are performed using picosecond pump-and-probe techniques at 82 MHz in both bulk GaAs and GaAs-AIGaAs multiple quantum well (MQW) etalons at room temperature. A 0.5 μm thick bulk GaAs crystal having no AIGaAs windows which was sandwiched between 98% reflecting mirrors completely recovered to its original transmission level in 150 ps (Fig. l) despite no intentional doping or damaging. With <30 ps overlap of the input and probe pulses, the total cycle time was <180 ps. The same etalon showed 5:1 contrast in the NOR gate driven by 7 pJ input. A 2×2 array of NOR gates was operated (at 82 MHz) in a MQW etalon having flatter mirrors than our previous etalons. The closest pixel spacing of >12 μm in this array is greater than the maximum displacement (about 10 μm ) at which a single input pulse produces a noticeable effect on a probe pulse. Thus we believe there is no appreciable crosstalk present. A "data diode" (unequal mirror reflectivities allows data to flow in only one direction) was demonstrated. While 5:1 contrast resulted with one side of the etalon facing the input beam, no effect of the input was evident when the other side faced the beam (Fig. 2).
Cascaded Bistable Optical Devices Based on Two Photon Absorption in Room Temperature InSb
Authors: Ji Wei , Kar A.K. , Keller U. , Mathew J.G.H. , Walker A.C.
Published: February 2023

InSb at room temperature exhibits significant dispersive nonlinearity at 10 μm as a result of generation of free carriers by a two-photon absorption process(1). This has enabled us to study optical bistability in InSb at room temperature using pulsed CO2 laser radiation(2).
Fabrication and Characterization of Arrays of GaAs All-Optical Logic Gates
Authors: Warren M. , Lee Y. H. , Olbright G. R. , Gibbs H. M. , Peyghambarian N. , Venkatesan T. , Wilkens B. , Smith J. S. , Yariv A.
Published: February 2023

In previous experiments with GaAs-based optical logic gates, the overall switching time of the devices was limited by the carrier relaxation time to several nanoseconds.1 The active regions of earlier devices were grown with "windows" of AIGaAs to reduce the exciton surface recombination rate. The present devices were produced from a 1.5-μm-thick GaAs layer grown by MBE without an AIGaAs window, resulting in an order-of-magnitude reduction in the recovery time.
Observation and Analysis of Critical Slowing Down in Nonlinear Visible Interference Filters
Authors: Mathew J.G.H. , Taghizadeh M.R. , Abraham E. , Janossy I. , Smith S.D.
Published: February 2023

We discuss our recent experimental and theoretical studies of the dynamics of switching in a bistable system consisting of ZnSe in the form of thin film interference filter1-3 structures operating in the 500 - 700 nm region of the spectrum. Theoretically, the system can be modelled as an absorbing thin layer of active material (ZnSe) evaporated on a semi-infinite slab of a non-absorbing substrate (glass). The solution of the heat equation can be expressed as a Volterra equation from which an approximate expression for the switch-up time can be derived, namely where w ≡ spot size, D ≡ thermal diffusivity of glass, Ps = threshold power, P0 ≡ holding power and P1 = P0 + power increment (stepwise) at t = 0.
Steady Characteristics of A Biased Optically Bistable Device
Authors: Golaire Ch. , Mandel Paul , Laws P.
Published: February 2023

We consider an optically bistable device illuminated by two incident beams: a biasing (or holding) beam which brings the system into a state appropriate to perform a given logic operation and a controlling (or address) beam. The refraction index is n=n0+n21I1c+n22I2c where Ikc is the cavity intensity of the beam k.
Ring Pattern of Thermal Self-Deforcusing
Authors: Li Chun-fei , Zhou Ping
Published: February 2023

A Gaussian beam travelling through an absorbing medium may exhibit some special ring patterns arising from the thermal self-deforcusing effect(1)–(3) In this paper an expression for the beam divergence was obtained from an optical ray equation and a thermal conductivity equation as follows: The first term is a nonlinear divergence angle, which depends on the incident laser power Po, the absorption coefficient ∝, the thermal conductivity coefficient K, temperature-refractive index coefficient dn/dT, and beam radius w. The second term is an initial divergence angle according to the curvature radius of Gaussian beam at the front end medium R.
Measurement of Transverse Coupling Between Adjacent InSb Optical Switching Elements
Authors: Hagan D.J. , Galbraith I. , Mackenzie H.A. , Firth W.J. , Walker A.C. , Young J. , Reid J.J.E. , Smith S.D.
Published: February 2023

Vast data processing rates of 1010 ~ 1012 bits per second have been predicted for parallel, all optical switching arrays(1). However, for reasons of economy of both space and energy the attainment of such rates will depend strongly upon the space-bandwidth (i.e. spatial resolution) of the array(2). Transverse coupling between switching elements must therefore be minimised to take full advantage of the potentially high data rates offered by optics.
Large Third Order Nonlinear Optical Susceptibilities in Organic Materials
Authors: Carter Gary M. , Chen Yung Jui , Thakur Mrinal K. , Hryniewicz John V. , Meyler Stephen E.
Published: February 2023

In order to realize certain ultrafast optical signal processing and logic concepts materials are needed with both a large and fast responding (in times less than a picosecond) third order nonlinear optical susceptibility χ(3) [1,2]. The speed of the nonlinear process is typically attained by using non-resonant excitation [1]. Further one must be able to obtain the material in the form required for the anticipated application; e.g., waveguides or etalons.
Where Conventional Computing Will Be Ten Years From Now
Authors: Armstrong John A.
Published: February 2023

This talk will attempt a projection of the capabilities of "conventional" semiconductor - based computing ten years from now. This will provide a context in which to understand the capabilities that optical computing will have to have to establish a foothold in the industry.
Noise Effects in Dispersive Optical Bistability
Authors: Lugiato L. A. , Colombo A. , Broggi G. , Horowicz R. J.
Published: February 2023

In a recent paper (1) we formulated a running wave, singlemode model for purely dispersive optical bistability, which incorporates amplitude and frequency fluctuations in the incident field, cavity length fluctuations, thermal noise in the radiation field and in the material. In the bad-cavity case of miniaturized bistable devices which utilize semiconductor dispersive media, our model reduces to a single stochastic differential equation for the material variable, which contains several terms of additive and multiplicative noise. In the white-noise case, it is equivalent to a Fokker-Planck equation in one variable, whereas in the case of colored noise it is equivalent to a multidimensional Fokker-Planck equation. On the basis of this model, we examined both problem of practical (P) and of fundamental (F) interest.
Nonlinear Surface Waveguides
Authors: Boardman A.D. , Cooper G.S. , Egan P.
Published: February 2023

The current state of knowledge of finite amplitude nonlinear surface-guided waves will be reviewed together with a limited indication of their potential for application in modern optical signal processing. Both TE and TM waves in planar guides and novel types of LP waves in optical fibres will be analysed but attention will be restricted to isotropic materials. These nonlinear waveguides have field distributions that are substantially altered as the light intensity increases. This means that the usual coupled-mode theory is inapplicable since the really interesting effects will occur near to the light-line. The nonlinearity arises from the symmetry-reduced third-order term in the electric polarisation or in some phenomenological fashion designed to fit experiment. This means that all processes occur at the same frequency and the standard boundary conditions apply. Self-focussing waves occur for which some kind of hysteretic switching schemes can be devised. It is emphasised, however, that this behaviour must not be taken as a definition of optical bistablity. Many types of waveguiding structures will be presented. These will be discussed physically in terms of the electric field distributions and the variation of the total power flow down the guide with the effective refractive index of the surface-guided wave. The differences between TE and TM waveguide structures and the role of saturation effects will be critically assessed as will the status of recent results concerning the prediction of optical bistablity in plane wave reflection-based devices. These will be contrasted with some recent results on the behaviour of laser beams in layered structures.
Bistable Optical Device Using Guided Mode Excitation in Silicon on Sapphire
Authors: Pardo F. , Koster A. , Chelli H. , Paraire N. , Laval S.
Published: February 2023

The device uses a cristalline silicon film, grown an a sapphire substrate, as nonlinear material. The film is considered as an optical waveguide, in which the excitation light is coupled by a diffraction grating etched on the silicon surface. The grating is covered with a silver layer to get better field enhancement in the waveguide. Light is then incident through the sapphire substrate. For an incidence angle slightly different from the resonance value, the guided mode is weakly excited at low incident power. As power increases, refractive index variations yield better excitation of the mode and bistable operation is predicted.
Intrinsic Optical Bistability in a Passive GaAlAs Waveguide
Authors: Walker A.C. , Aitchison S. , Chilwell J. , Ritchie S.T.D. , Rodgers P.M.
Published: February 2023

Intrinsic optical bistability has been observed in a GaAlAs slab waveguide as a result of a dispersive nonlinearity. The guiding layer was 1.7 μm thick, contained ~ 7% Al and was bounded by GaAlAs layers of higher Al content. An optical cavity was formed by cleaving the guide ends and leaving these surfaces uncoated (~ 32% reflectivity). The length of the cavity was ~ 200 μm.
Instabilities in Self-Pumped Barium Titanate Phase-Conjugate Mirrors
Authors: Narum Paul , Gauthier Daniel J. , Boyd Robert W.
Published: February 2023

It has been demonstrated by several authors that an optical resonator coupled with an externally pumped1 or self-pumped2,3 barium titanate (BaTiO3) phase-conjugate mirror (PCM) exhibits instabilities in the intensity and spectrum of the output. These results have been associated with transverse mode instabilities in the phase-conjugate resonator or with longitudinal mode instabilities of the pump laser, respectively. We have observed instabilities in the reflected intensity and in the frequency shift of the phase-conjugate return which is an inherent property of the self-pumped PCM.
Optical Bistability with Two-State Atoms: Steady States and Dynamical Instabilities
Authors: Kimble H. J. , Rosenberger A. T. , Orozco L. A. , Raizen M. S.
Published: February 2023

Beams of homogeneously broadened two-state sodium atoms in a confocal ring resonator have been employed to investigate the steady-state characteristics of absorptive [1] and dispersive optical bistability. Also studied in the same system is the dynamical behavior due to the intrinsic single-longitudinal-mode instability [2] originating in the alteration of the atomic absorption profile by a strong field as in the Lorenz-type instability in the homogeneously broadened laser. All experimental parameters are carefully measured and corrected for transit broadening, finite absorption, and residual Doppler broadening in order to be able to make an absolute comparison with the single-Gaussian-transverse-mode theory [3-6]. Despite the frequency degeneracy of the transverse modes of the resonator, the agreement with this theory for absorptive bistability is remarkably good. The dispersive bistability data are more difficult to interpret, but they seem to be in reasonable agreement with the theory; the same can be said of the results for the domain and oscillation frequency of the instability, at least within a certain region of parameter space. Outside this region, multiple unstable states appear for various intracavity intensities; recent observations suggest that these may be due in part to instabilities involving higher-order transverse modes of the resonator.
Stark Effect on a Ground State Exciton Confined in Three Dimensions
Authors: Dagenais M. , Sharfin W.F.
Published: February 2023

We report the first measurement of the quadratic Stark shift of the bound exciton ground state (D°X) in the direct gap CdS semiconductor. The exciton is confined in three dimensions by the potential of a neutral donor (Li or Na interstitials) which restricts the exciton motion over dimensions of order of the free exciton Bohr radius (30 Å). Optical transmission measurements with a single mode dye laser reveal a very narrow linewidth (8-10 GHz) which implies a very well defined and reproducible potential well. This is in sharp contrast to previous realizations of three dimensional excitonic confinement where linewidths about 1000 times larger are commonly observed because of the large variations of the potential dimensions. At an electric field of 2.5 x 104 V/cm, a shift of the bound exciton resonance as large as its half-width at half-height is observed without any appreciable broadening of the resonance. The bound exciton shift is about 25 times smaller than the free exciton Stark shift measured in the same experimental conditions.
Nonlinear Effects in Waveguide Devices
Authors: Silberberg Yaron , Sfez Bruno G.
Published: February 2023

All-optical switching and routing of light in fibers and waveguides has the potential of handling optical signals at ul rahigh speed. By using very rapid electronic nonlinearities in transparent materials, extremely fast switching free of thermal problems could be obtained. The guided wave environment reduces the peak power requirements. Although the transit times may be long, these devices operate in a "pipeline" scheme, allowing very fast rates. A number of nonlinear devices have been considered for all-optical switching, including nonlinear directional couplers, Mach-Zehnder interferometers and mode-splitters. We will review these in the first part of the talk.
Dynamic Operation of a Nonlinear Waveguide for Optical Logic
Authors: Niepceron A. , Koster A. , Paraire N. , Carton M. , Laval S.
Published: February 2023

Experimental study of an annealed Silicon-on-Sapphire nonlinear waveguide in the pulsed regime can show two consecutive subnanosecond switchings allowing its operation as an optical logic gate.
Squeezing in Bistable Optical Systems
Authors: Reynaud S. , Giacobino E.
Published: February 2023

It is known that optical bistable systems are capable of generating squeezed states of light ([1] [2]). Perfect squeezing is achievable for the outgoing field in the following configuration: operation near the critical point of a single-ended cavity containing a (noise-free) dispersive non-linear medium ([3]).
Nonlinear Bragg Reflectors with Doping Superlattices
Authors: Kost A. , Garmire E. , Danner A. , Dapkus P. D.
Published: February 2023

Distributed feedback structures (DFBs) with a nonlinear index of refraction have been investigated theoretically1 and optical bistability has been demonstrated in a distibuted feedback semiconductor laser amplifier2. As of yet, however, the full potential of a passive nonlinear DFB has not been realized. Recent developments in the design and fabrication of semiconductor heterostructures have made passive DFBs attractive candidates for all optical swiches. These developments include: (1) The epitaxial growth of high reflectivity all semiconductor mirrors (Bragg reflectors)3 and (2) The fabrication of doping supperlattices which exhibit large optical nonlinearites at low levels of illumination4 and which can easily be incorporated into a Bragg reflector.
Strong Nonlinear Optical Resonances in CdSe with Picosecond Response Time
Authors: Dörnfeld Claus , Hvam J. M.
Published: February 2023

The nonlinear optical properties of semiconductors are conveniently studied in a four-wave mixing experiment. We have performed such experiments in CdSe at low temperatures, using a synchronously pumped DCM dye-laser with a pulse lenght of 1.4 ps.
An Electron-Beam Controlled SLM Based on a Bistable Nonlinear Interference Filter
Authors: Walker A.C. , Smith S.D. , Campbell R.J. , Mathew J.G.H.
Published: February 2023

Optothermal optically nonlinear interference filters (NLIFs) have been exploited as bistable switches for some years [1-3]. Recently we have developed an electron-beam tuned interference filter spatial light modulator (ETIF-SLM) based on such nonlinear devices [4]. A number of ETIF-SLM devices have been made for operation at 514 nm and 633 nm wavelengths. They were based on standard, Thorn-EMI type 8541, vidicon tubes which had, in place of the photo-cathode, the NLIF deposited on the inside surface of the faceplate prior to sealing onto the vacuum tube. The NLIFs incorporated ZnSe spacers and were matched by a λ/4 TiO2 layer into an optically opaque Si layer and the final top layer was ~ 100 nm of Al added to provide a return current path. For these initial studies the e-beam power was increased by opening the gun aperture to give 0.1 - 1 mA of beam current and the target voltage set to 500 V - 1 kV - providing 100 mW to 1 Watt of e-beam power.
CdS self-electrooptic effect device: electrooptic modulation and optical bistability at 514nm
Authors: Witt A. , Wegener M. , Klingshirn C. , Gnass D. , Iyechika Y. , Jäger D.
Published: February 2023

It has been demonstrated that thin CdS crystal platelets at room temperature may exhibit all-optical bistability under illumination with the 514nm line of an Ar+-laser1. In this case the local heating of the sample leads to induced absorption optical bistability. In the present paper we evaporate metallic contacts on CdS crystals and apply an external bias voltage. The carriers created by the incoming light lead to a photo-current which in turn increases the temperature of the sample by electrical power via Joule's heat and thereby changes the optical properties 2,3.
Spontaneous Spatial Symmetry Breaking in Passive Nonlinear Optical Feedback Systems
Authors: Adachihara H. , McLaughlin D.W. , Newell A.C. , Quarzedinni A. , Moloney J.V.
Published: February 2023

In an earlier paper [1] we derived a formula describing a modulational instability on the plane or quasi-plane wave background of the field in a passive nonlinear optical ring cavity. This formula was applied to the specific case of the eigenvalue of the linearization of the fixed point going through -1 signifying a period doubling bifurcation. The Ikeda plane wave instability analysis was shown to be invalid, indicating that such fixed points are unstable to transverse fluctuations. We will show that this formula is universally applicable to feedback systems exhibiting strong nonlinear dispersion. We recover, as a special case, the recent mean field result of Lugiato et al. [2] in the case where the above eigenvalue approaches +1, signifying a saddle-node bifurcation. The modulational instability is of widespread occurrence even in situations where the plane wave solution (K
T
= 0) is strongly damped. It explains the occurrence of upper bistable branch solitary wavetrains [3] and shows that the dynamical switching from a low to high transmission state with transverse spatial rings occurs via nonlinear generation of higher harmonics in K
T
space.
First Passage Time Distribution for Delayed Laser Threshold Instability
Authors: Miguel M. San , Torrent M. C.
Published: February 2023

The delay in the observation of a bifurcation induced by a sweep of the control parameter has been studied in a variety of - optical instabilities 1). Most theoretical studies give a deterministic description of the problem. We address here this question through a stochastic dynamics characterization. The delay is due to a dynamical stabilization and the stability is here associated with the lifetime of a state. The lifetime is defined as a Mean - First Passage Time (MFPT) to reach a certain threshold observable value. This is identified with the time at which the instability is observed. Such identification gives an operational definition of the dynamical bifurcation point and the observed delay.
Switching Dynamics of Bistable CdS Absorptive Platelets
Authors: Bigot J-Y. , Daunois A. , Eddeqaqi N. Cherkaoui , Oberlé J. , Wegener M. , Klingshirn C.
Published: February 2023

The switching dynamics of thermally induced optical bistability due to increasing absorption is investigated in thin CdS platelets, at room temperature. The sample, held on its high transmission level by a cw argon laser beam, is switched by an external UV light pulse from an excimer laser (wavelength 308 nm, duration 15 ns). Fast switching or slowing down are possible, depending on the holding cw intensity and on the pulse energy. A detailed study of the switching time shows that a very rapid component is first observed (electronic contribution), followed by a much slower component (thermal relaxation of the material). This slow component can be avoided for high enough switching pulse energies. The transverse relaxation of the temperature in the sample appears to influence strongly the switching dynamics.
Improved performance of bistable CdSe filters
Authors: Sahlén Olof , Öhlander Ulf , Olin Ulf
Published: February 2023

Thermally evaporated ZnS and ZnSe filters have attained much interest since the first (Ref 1) demonstration of optical bistability in these materials (Refs 2-6). Recently we have also demonstrated optical bistability in CdSe filters (Ref 7).
Nonlinear Refraction and Increasing Absorption in HgCdTe Optical Bistability at Room Temperature: an Experimental Study
Authors: Coppo P.M. , Cecchi S. , Salieri P. , Arecchi F.T.
Published: February 2023

Many authors have experimentally examined the nonlinearities of HgCdTe at resonance with the CO2 laser wavelength [1]. At room temperature non1inearities of electronic origin, arising from band filling, are weak because of Auger recombination and are masked by thermal effects. In this communication we extend the analysis of ref. 1 on thermally induced optical bistability at low power: we show, for the first time in HgCdTe, the appearance of clockwise hysteresis cycles in transmission as input power Pi is increased, due to nonlinear absorption. We can account for both absorptive and refractive nonlinear contributions by simultaneous monitoring of transmission and reflection. The Hg0.815Cd0.185Te plates (280 um in thickness, with doping pa =1*1016 cm-3, prepared and polished by Elettronica SpA) were placed without heatsinking in a thermally controlled environment. In Fig. 1 the transmitted (Pt) and reflected (Pr) power is shown as a function of Pi: the three data sets differ in cavity mistuning. The thermooptic effect was measured directly, by a close focus optical pyrometer, and indirectly by taking data at different thermal bath temperature T. The values of Pi at the hysteresis associated to a given cavity interference order (indicated with the symbols of Fig. 1c) drift with T (Fig. 2): the maximum induced temperature increase is inferred to be 30-35°C, with steps of 2.5-3.5°C at the switching points, and a value of dn/dT = -2.8*10-3 K-1 is deduced. Fig. 3 presents numerical results (to be compared with Fig. 1b) obtained parametrically solving the nonlinear Fabry Perot equations using the absorption measured after AR coating one sample face. This nonlinear absorption will be discussed in terms of a free carrier origin.
Optical Transistors with Negative Feedback
Authors: Mandel Paul , Smith S.D.
Published: February 2023

We consider a Fabry-Perot filled with a nonlinear medium. The transmitted (It) and reflected (Ir) intensities are related to the holding or input beam intensity Ih by the Airy formulae: It is assumed that the angle of incidence is sufficiently small (i.e., near normal incidence) to neglect the angular dependence in the Airy function. Two situations have been analysed, depending on whether the reflected beam is fed back into the Fabry-Perot with the same angle of incidence as the holding beam or not. In both cases the reflected beam goes through an attenuator which reduces the intensity by a coefficient α. The coefficient α varies from 0 (no attenuation) to 1 (complete attenuation).
Optical Bistability in Active Devices
Authors: Kawaguchi Hitoshi
Published: February 2023

Optical bistability in both FP and DFB type LDs is an interesting subject because they have optical gain. Optical gain results in advantages such as low switching optical power, high ON-OFF ratio, and large fan-out. Bistable LDs can also operate faster than one nanosecond. Recent work in our laboratory, as well as by others in the field, will be reviewed.
Regular and Chaotic Dynamics of Optically Pumped Molecular Lasers
Authors: Harrison R.G. , Moloney J.V. , Forysiak W. , Uppal J.S.
Published: February 2023

Optically pumped molecular lasers (OPML) have been suggested recently as possible candidates for the observation of Lorenz type chaos in a laser system. Efforts have been made to truncate the larger system of coupled ODE's to a set of three [1], a truncation that we feel is not physically justified [2]. It does not appear to be appreciated in the laser theory literature that larger systems of coupled ODE's or even partial differential equations (PDE's) may exhibit Lorenz-type chaotic behaviour in some parameter window making unphysical truncation unnecessary. We contend that OPML lasers themselves represent the canonical laser dynamical system retaining, as we shall show, simplicity in the underlying physics while being amenable to a dynamical systems analysis at a level of say the Lorenz equations. Moreover, new nonlinear dynamical features emerge which can be directly related to the distinct physical processes operative in the laser. The wealth of novel nonlinear dynamical behaviour which emerges at parameter values readily achievable in experimental OPML systems makes the recent experimental observations by Weiss et al [3] particularly relevant.
Spatial Bistability, Instabilities and Chaos in Nonlinear Optical Systems with Two Dimensional Feedback
Authors: Akhmanov S. A.
Published: February 2023

The subject of my paper is connected with the experimental observation and theory of a new class of effects in non-linear optical resonators. All the effects are due to the two-dimensional feedback, i.e. different transverse transformations of optical field (shifts, rotations, diffusion, stretching, compression, etc.) in a feedback loop.
External Grating Couplers on Planar Waveguides as Integrated Optical Bistable Devices
Authors: Briguet V. , Kramer J. , Lukosz W.
Published: February 2023

The 'external' grating coupler is a diffraction grating pressed against the planar waveguide in a similar way as a prism coupler. Such couplers have, to the best of our knowledge, not been used in integrated optics. The couplers normally used are surface relief gratings on the waveguide. We report on a new type of optical bistability (OB) which occurs only with external but not with normal grating couplers. The air gap of width d, where 0≤d≤λ, plays an essential role in the OB mechanism.
Two-Frequency Competition in External Cavity Semiconductor Lasers
Authors: Tatah Karim , Garmire Elsa
Published: February 2023

Electrical feedback on external cavity semiconductor lasers exhibit novel long periodic oscillations. Current modulation generates locked oscillations at new frequencies following the Farey hiearchy.
Optimised instability thresholds in a nonlinear Ring-Cavity
Authors: Firth W.J. , Sinclair S.W.
Published: February 2023

Optical bistability (OB) and instabilities in passive ring resonators containing Kerr media are described by the delay-differential system [1]: where E(t) is the intracavity field, τ the medium response time and ϕO the cavity mistuning. The nonlinear phase shift is denoted by ϕ(t).
Optical Nonlinearities of Quantum-Confined Excitons in Cubr Microcrystallites
Authors: Woggon U. , Henneberger F.
Published: February 2023

We have investigated both the linear and nonlinear absorption of CuBr microcrystallites (MC’s). The linear absorption spectrum is dominated by pronounced exciton peaks similar to bulk CuBr. The quantum confinement is evidenced by the increasing blue shift of the peaks with decreasing MC radius. We concentrate on the situation of RMC≫REXCITON (experiment : factor 10), where fluctuations of RMC are smaller than 10% as found from X-ray studies and where the experimental spectra can be well explained in terms of the exciton centre-of-mass quantum confinement. At resonant excitation with dye laser pulses we observe a pronounced bleaching of the exciton absorption with rising intensity accompanied by a blue shift of the absorption maximum. We have calculated the energy-shift of the exciton resonance for a high-density exciton gas confined to a MC in Hartree-Fock approximation and good agreement with the experimental data is obtained. At 77K we find a Lorentzian saturation intensity of about 100 kW/cm2 and a contrast as large as 30. Operation of the nonlinearity at room temperature with no significant difference to 77K is demonstrated. The results evidence that excitons in MC's give rise to larger optical nonlinearities than in the bulk material.
Photorefractive grating build-up by a 28 picosecond light pulse in B.S.O.
Authors: Jonathan J.M.C. , Roosen G. , Roussignol Ph.
Published: February 2023

The photorefractive effect has been intensively studied for its wide range of potential applications. Photorefractive crystals are insulators exhibiting both photoconductivity and electrooptic effect. The light induced redistribution of charge carriers generates a space charge field that modulates the refractive index. The simple model in which a single type of charge carriers are excited from and recombined to a single type of sites has been described many times. It/as been improved by introducing either new sites or both types of carriers. The experimental verifications that have been performed with nanosecond light pulses (BSO, BaTiO3 , LiNbO3) or picosecond light pulses (GaAs, BaTiO3) always led to a build up of the photo- refractive grating within the pulse duration.
Drift calibration method of Fabry-Perot filters using two-stage decomposition and hybrid modeling
Authors: Sheng Wenjuan , Zhan Jun , Wen Jianxiang , Peng G. D.
Published: February 2023

Although tunable Fabry-Perot (F-P) filters are widely acknowledged as fiber Bragg grating (FBG) demodulators, F-P filters exhibit drift error when subjected to ambient temperature and piezo-electrical transducer (PZT) hysteresis. To address the drift issue, the majority of the existing literature makes use of additional devices like the F-P etalon and gas chamber. In this study, a novel drift calibration method based on two-stage decomposition and hybrid modeling is proposed. The initial drift error sequences are broken down into three frequency components using the variational mode decomposition (VMD), and the medium-frequency components are further broken down using the secondary VMD. The initial drift error sequences are significantly simplified by the two-stage VMD. On this foundation, the long short-term memory (LSTM) network and polynomial fitting (PF) are used to forecast the low-frequency and high-frequency drift errors, respectively. The LSTM enables the prediction of intricate nonlinear local behaviors, while the PF method predicts the overall trend. The benefits of LSTM and PF can be effectively utilized in this manner. Compared to the single-stage decomposition, two-stage decomposition achieves superior results. The suggested method is an affordable and effective alternative to the current drift calibration techniques.
Liquid-crystal based drift-free polarization modulators: Part II. Ultra-stable Stokes and Mueller polarimeters
Authors: Rehbinder Jean , Dellinger Jean , Varin Briséis , Torzynski Marc , Takakura Yoshitate , Heinrich Christian , Zallat Jihad
Published: February 2023

We have previously reported a new design for drift-free liquid-crystal polarization modulators (LCMs) based on liquid-crystal variable retarders (LCVRs). Here, we study their performance on Stokes and Mueller polarimeters. LCMs have polarimetric responses similar to LCVRs and can be used as temperature-stable alternatives to many LCVR-based polarimeters. We have built an LCM-based polarization state analyzer (PSA) and compared its performance to an equivalent LCVR-based PSA. Our system parameters remained stable over a wide range of temperature, precisely from 25°C to 50°C. Accurate Stokes and Mueller measurements have been conducted, paving the way to calibration-free polarimeters for demanding applications.
Time-dependent band position difference between vibrational sum and difference frequency generation: a phenomenon originating from dispersion in the visible pulse
Authors: Guo Wei , Zhu Zulin , Liu Xiaolin , Ning Qianqian , Song Qiantong , Wang Yue , He Yuhan , Wang Zhaohui
Published: February 2023

Vibrational spectroscopy is significant for identifying chemical specification. Here, the spectral band frequencies corresponding to the same molecular vibration in sum frequency generation (SFG) and difference frequency generation (DFG) spectra present delay-dependent deviation. Through numerical analysis of time resolved SFG and DFG spectra with a frequency marker in the incident IR pulse, the frequency ambiguity was not caused by any structure and dynamic variation on the surface, but from the dispersion in the incident visible pulse. Our results provide a helpful method to correct the vibrational frequency deviation and improve the assignment accuracy for SFG and DFG spectroscopies.
Broadband 2D phase-gradient metasurface for linearly-polarized waves by suppressing Lorentz resonance of meta-atoms
Authors: Wang Zhenxu , Fu Xinmin , Liang Jian-gang , Wang Jiafu , Han Yajuan , Ding Chang , Qu Shaobo
Published: February 2023

Metasurfaces have exhibited versatile capacities of controlling electromagnetic (EM) waves due to the high degree of freedom of designing artificially engineered meta-atoms. For circular polarization (CP), broadband phase gradient metasurfaces (PGMs) can be realized based on P-B geometric phase by rotating meta-atoms; while for linear polarization (LP), realization of broadband phase gradients has to resort to P-B geometric phase during polarization conversion and polarization purity has to be sacrificed for broadband properties. It is still challenging to obtain broadband PGMs for LP waves without polarization conversion. In this paper, we propose the design of 2D PGMs by combining the inherently wideband geometric phases and non-resonant phases of meta-atom, under the philosophy of suppressing Lorentz resonances that usually bring about abrupt phase changes. To this end, an anisotropic meta-atom is devised which can suppress abrupt Lorentz resonances in 2D for both x- and y-polarized waves. For y-polarized waves, the central straight wire is in perpendicular to electric vector Ein of incident waves, Lorentz resonance cannot be excited although the electrical length approaches or even exceeds half a wavelength. For x-polarized waves, the central straight wire is in parallel with Ein, a split gap is opened on the center of the straight wire so as to avoid Lorentz resonance. In this way, the abrupt Lorentz resonances are suppressed in 2D and the wideband geometric phase and the gradual non-resonant phase are left for broadband PGM design. As a proof of concept, a 2D PGM prototype for LP waves was designed, fabricated and measured in microwave regime. Both simulated and measured results show that the PGM can achieve broadband beam deflection for reflected waves for both x- and y-polarized waves in broadband, without changing the LP state. This work provides a broadband route to 2D PGMs for LP waves and can be readily extended to higher frequencies such as terahertz and infrared regimes.
Determining the absolute temporal field of ultra-broadband terahertz-infrared pulses with field-induced second-harmonic spectrograms
Authors: Thomson Mark D. , Warawa Konstantin , Meng Fanqi , Roskos Hartmut G.
Published: February 2023

We demonstrate the use of spectrograms of the field-induced second-harmonic (FISH) signal generated in ambient air, to reconstruct the absolute temporal electric field of ultra-broadband terahertz-infrared (THz-IR) pulses with bandwidths exceeding 100 THz. The approach is applicable even with relatively long (150-femtosecond) optical detection pulses, where the relative intensity and phase can be extracted from the moments of the spectrogram, as demonstrated by transmission spectroscopy of very thin samples. Auxiliary EFISH/ABCD measurements are used to provide the absolute field and phase calibration, respectively. We take into account the beam-shape/propagation effects about the detection focus on the measured FISH signals, which affect the field calibration, and show how an analysis of a set of measurements vs. truncation of the unfocused THz-IR beam can be used to correct for these. This approach could also be applied to the field calibration of ABCD measurements of conventional THz pulses.
Birefringence based multi-focus fs/ps-CARS spectroscopy for thermometry and hyperspectral microscopy
Authors: Lin Elodie , Scherman Michael , Santagata Rosa , Bresson Alexandre , Attal-Tretout Brigitte
Published: February 2023

We present a multi-focus fs/ps-CARS scheme to perform spectroscopy on multiple points simultaneously for gas phase measurements and microscopy, using a single birefringence crystal or a combination of birefringent stacks. CARS performances are first reported for 1 kHz single-shot N2 spectroscopy on two points set few millimeters apart, allowing thermometry measurements to be carried out in the vicinity of a flame. Then, simultaneous acquisition of toluene spectra is demonstrated on two points set 14 µm apart in a microscope setup. Finally, two-point and four-point hyperspectral imaging of PMMA microbeads in water is performed, demonstrating a proportional increase in acquisition speed.
Voltage-tunable Q factor in a photonic crystal microcavity
Authors: Krasnov A. I. , Pankin P. S. , Buzin D. S. , Romanenko G. A. , Sutormin V. S. , Zelenov F. V. , Masyugin A. N. , Volochaev M. N. , Vetrov S. Ya. , Timofeev I. V.
Published: February 2023

A photonic crystal microcavity with a tunable quality factor (Q factor) has been implemented on the basis of a bound state in the continuum using the advanced liquid crystal cell technology platform. It has been shown that the Q factor of the microcavity changes from 100 to 360 in the voltage range of 0.6 V.
Graphene perfect absorber based on degenerate critical coupling of toroidal mode
Authors: Xu Rongyang , Fujikata Junichi , Takahara Junichi
Published: February 2023

Graphene is a two-dimensional material with great potential for photodetection and light modulation applications owing to its high charge mobility. However, the light absorption of graphene in the near-infrared range is only 2.3%, limiting the sensitivity of graphene-based devices. In this study, we propose a graphene perfect absorber based on degenerate critical coupling comprising monolayer graphene and a hollow silicon Mie resonator array. In particular, monolayer graphene achieves perfect absorption by controlling the periods and holes of the Mie resonators. The proposed graphene perfect absorber can significantly improve the sensitivity of graphene-based devices.
Color 3D display and security via monochrome scenes
Authors: Guo Junfeng , Kou Yu , Kim Seok-Tae , Li Xiaowei
Published: February 2023

Color three-dimensional (3D) displays have always been the ideal display method because of their strong sense of reality, whereas color 3D displays of monochrome scenes are still challenging and unexplored. A color stereo reconstruction algorithm (CSRA) is proposed to solve the issue. We design a deep learning-based color stereo estimation (CSE) network to obtain color 3D information of monochrome scenes. The vivid color 3D visual effect is verified by our self-made display system. Furthermore, an efficient CSRA-based 3D image encryption scheme is achieved by encrypting a monochrome image with two-dimensional double cellular automata (2D-DCA). The proposed encryption scheme fulfills the requirement for real-time and high-security 3D image encryption with a large key space and the parallel processing capability of 2D-DCA.
Multiaxial super-geometric mode laser
Authors: Pan Jing , Wang Zhaoyang , Zhan Ziyu , Fu Xing , Shen Yijie , Liu Qiang
Published: February 2023

Structured light was usually studied by two-dimensional (2D) transverse
eigenmodes. Recently, the three-dimensional (3D) geometric modes as
coherent superposed states of eigenmodes opened new topological
indices to shape light, that optical vortices can be coupled on
multiaxial geometric rays, but only limited to azimuthal vortex
charge. Here, we propose a new structured light family, multiaxial
super-geometric modes, enabling full radial and azimuthal indices
coupled to multiaxial rays, and they can be directly generated from a
laser cavity. Exploiting combined intra- and extra-cavity astigmatic
mode conversions, we experimentally verify the versatile tunability of
complex orbital angular momentum and SU(2) geometry beyond the limit
of prior multiaxial geometric modes, opening new dimensions to
revolutionize applications such as optical trapping, manufacturing,
and communications.
Photoacoustic maximum amplitude projection microscopy by ultra-low data sampling
Authors: Cheng Zhongwen , Wang Delin , Zhang Zhenhui , Wang Zhiyang , Yang Fei , Zeng Lvming , Ji Xuanrong
Published: February 2023

Photoacoustic microscopy (PAM) has attracted increasing research interest in the biomedical field due to its unique merit of combining light and sound. In general, the bandwidth of a photoacoustic signal reaches up to tens or even hundreds of MHz, which requires a high-performance acquisition card to meet the high requirement of precision of sampling and control. For most depth-insensitive scenes, it is complex and costly to capture the photoacoustic maximum amplitude projection (MAP) images. Herein, we propose a simple and low-cost MAP-PAM system based on a custom-made peak holding circuit to obtain the extremum values by Hz data sampling. The dynamic range of the input signal is 0.01–2.5 V, and the −6-dB bandwidth of the input signal can be up to 45 MHz. Through in vitro and in vivo experiments, we have verified that the system has the same imaging ability as conventional PAM. Owing to its compact size and ultra-low price (approximately $18), it provides a new performance paradigm for PAM and opens up a new way for an optimal photoacoustic sensing and imaging device.