bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of an Actively Mode-Locked Nd:YAG Laser
Authors: Cormier Jean-François , Morin Michel , Piché Michel
Published: February 2023

The distinction between deterministic and stochastic instabilities in actively mode-locked lasers is investigated theoretically and experimentally. A linear stability analysis performed on the gaussian iterative model predicts deterministic instabilities. Experiments made with a Nd:YAG laser have revealed the appearance of periodic instabilities as the modulation frequency is detuned from optimum. Spontaneous emission can trigger periodic Q-switching with an apparently deterministic character.
Simulation of the Self-Pulsing Instability in an Inhomogeneously Broadened Single-Mode Laser by the Finite-Dimensional Model
Authors: Toronov V. Yu.
Published: February 2023

We have investigated numerically the behaviour of the inhomogeneously broadened medium of single-mode unidirectional Lorentz-broadened laser in the self-pulsing regime. On the basis of this analysis, we have constructed the five-order set of differentional equations, which well describes the self­pulsing instability in laser in a certain band of the gain.
Global Bifurcation in the Driven CO2 Laser
Authors: Schwartz Ira B.
Published: February 2023

Nonlinearly driven lasers are an excellent testbed for studying the phenomenology of nonlinear dynamics. In [1] and [2], a wide variety of behavior is observed experimentally: e.g., bistability, hysteresis, and period doubling cascades to chaos. Although much analysis to date on the nonlinear driven laser has been local [3,5], in this paper we discuss the global bifurcations in terms of the modulation amplitude [4].
Influence of Moving Diaphragm on Gas Laser Dynamics
Authors: Smirnov V. N. , Strokovsky G. A.
Published: February 2023

The onset of different dynamic operation regimes in ring gas laser with internal cylindrical diaphragm moving along resonator axis is experimentally and theoretically investigated. Peculiarities of generation regimes are explained by modulation of diffraction phase coupling of counterpropagating waves due to backscattering on moving diaphragm.
Bifurcations of the Period Adding and Transitions to Chaos in a Laser Generator with Delayed Feedback
Authors: Anishchenko V. S. , Bogoroditsky A. G. , Rabinovich E. M.
Published: February 2023

The bifurcation analysis of the investigated mapping dynamics together with the experimental evidence make it possible to assert that we observe a nontraditional transition to chaos, which is typical for a wide class of dynamical systems with a specific form of nonlinearity.
Behavior of a Bidirectional CO2 Ring Laser
Authors: Dennis Michael L. , Diels Jean-Claude
Published: February 2023

Stable antiphase modulation and bidirectional cw operation is observed with a DC pumped CO2 ring laser, injecting a low frequency modulation results in complex dynamics.
Phase and Amplitude Correlations in the Transient Evolution of a Detuned Laser after Switch-On
Authors: Ciuchi S. , De Pasquale F. , San Miguel M. , Abraham N. B.
Published: February 2023

We investigate correlations in the evolution of the phase and amplitude of a laser during the transient after it is switched on. In particular we seek differences in these correlations for resonantly tuned lasers and for detuned lasers since the deterministic switch-on to non-resonant operating conditions involves a frequency shift as the intensity increases [1]. We consider the effect of different noise strengths but we limit our analysis to a "good cavity" condition and to third-order terms in the gain saturation. We discover a crossover from a low detuning regime, in which the initial phase diffusion in the unstable "off-state" gives the dominant contributions to the coupled phase-intensity fluctuations in the switching transients, to a large detuning regime in which the evolution of the laser frequency (driven by the evolving intensity) dominates.
Intermittent Dynamics Driven by Band-Limited Noise
Authors: Gammaitoni L. , Marchesoni F. , Menichella-Saetta E. , Santucci S.
Published: February 2023

We study the intermittent dynamics of a nonlinear system driven by band-limited noise. Intermittent bursts are revealed through analogue simulation and their statistics are summarized.
1/f Noise in Semiconductor Lasers and Its Reduction
Authors: Hua Li , Abraham N. B.
Published: February 2023

A Combination of optical and electrical feedback to suppress frequency noise of semiconductor laser is studied theoretically by adding a 1/f noise source in the laser equations and calculating the frequency noise spectrum. The feedback suppression is realized experimentally.
Quantum Noise in Nondegenerate Four-Wave Mixing Above Threshold
Authors: Brambilla M. , Strini G. , Castelli F. , Lugiato L. A. , Prati F.
Published: February 2023

The multimode instability in optical bistability is a relevant example of nondegenerate four-wave mixing, which allows for a fully quantum microscopic theory. We calculate the spectrum of the intensity fluctuations beyond the instability threshold .
Quasi-Soliton Within a Distributed Bistable Optical System
Authors: Surdutovich G. I.
Published: February 2023

In an arbitrary bistable distributed system -e.g. passive ring resonator with nonlinear medium and stationary input signal - spatially limited solitary initial perturbation (seed pulse) of a sufficiently large amplitude and arbitrary form turns into an asymtotically rectangular pulse with exponentially small instability increment (quasisoliton). The properties of the quasisoliton are analized within the frames of a different dispersion models. Such a quasisoliton regime was realized experimentally in acousto-electronic model system and in the system with bicompound injection laser and external cavity.
Maxwell-Bloch Theory in A Nonideal Fabry-Perot Cavity
Authors: van Wonderen A.J. , Suttorp L.G.
Published: February 2023

In recent years it has become clear that the Maxwell-Bloch theory is capable of providing reliable predictions on instabilities in nonlinear media. For instance, it is successful in describing the single-mode instability of optical bistability [1]. Also for active media important results have been achieved on the basis of the Maxwell-Bloch theory [2].
Quantum Stairs and Multi-Rabi Chaos in a Driven Anharmonic Oscillator
Authors: Kaplan A. E.
Published: February 2023

A single magnetized electron driven by the EM wave in the vicinity of the cyclotron frequency can exhibit large hysteretic resonance caused by a tiny relativistic change of its mass [1]. Consistent with the theory [1] this effect has recently been observed in experiment [2]. The theory of this most fundamental multi-stable interaction of light with matter can be developed using a simple model of a quantum anharmonic oscillator driven by a periodic force. Making a common assumption that quantum transitions occur only between neighboring slightly-nonequidistant eigenstates of the oscillator, one can describe the dynamics of the system by infinite number of coupled kinetic equations for the density matrix elements at each eigenstate. We found that the reaction of the system (expressed in the terms of expectation energy of excitation) dramatically depends on the speed of sweeping frequency of the driving force near the cyclotron resonance. If the driving frequency is swept downward infinitesimally slow and no dissipation is present, the system’s response shows strongly pronounced train of "quantum stairs" at the raising slope of the function "energy vs. driving frequency" (Fig. 1) starting at the main (cyclotron) frequency Ωr which is a resonant frequency of the unperturbed (i.e. harmonic) oscillator. The height of each of these stairs is ħΩr and they are equidistantly spaced by ΔΩsp = Ωn−Ωn−1 such that ΔΩsp/Ωr = ħΩr/moc2 = krre/α, where kr = Ωr/c, re = e2/moc2 is a classical electron radius, and α = e2/ħc = 1/137 is a fine structure constant; e.g., at λr = 2mm, ΔΩsp = 180.76 Hz. The stair of each consequent order n can be interpreted as an adiabaticly slow Landau-Zenner transition between (n-1)th and n-th excited level respectively. However, when the frequency sweeping is sufficiently fast, these transitions become oscillatory with the oscillations at each one of them being due to a Rabi frequency pertinent to that individual transition. Since all of them are coupled and since due to the anharmonicity all the Rabi oscillations form an infinite set of incommensurate frequencies, these oscillations evolve into strongly chaotic motion (Fig. 2). These quantum effects are universal and should exist in any anharmonic oscillator as long as its anharmonicity is much stronger than dissipation, i.e. when ΔΩspτ ≫ 1, where τ is relaxation time of the system (for a single cyclotron electron with its energy dissipation attributed to the synchrotron radiation, ΔΩspτ = 3/2α = 205.5). This work is supported by AFOSR.
Manifestations of Chaos in a Conservative Nonlinear Quantum System
Authors: Kronmiller D. L. , Cantrell C. D.
Published: February 2023

We study the transition from classical to quantum chaos by examining the time series defined by the quantum expectation values of time-varying observables.
Adaptive Search with Chaos in Nonlinear-Optical Systems
Authors: Davis Peter
Published: February 2023

Simulations of nonlinear optical systems with adaptive control have shown the potential usefulness of chaos for search among attractors. We present examples of two types of adaptive search using chaos. In the first example, adaptive feedback to an excitation parameter in a nonlinear optical resonator is used to control bifurcation between a regime where a set of modes is stable and a regime where there are chaotic transitions between the modes. The second example is a model of a network in which adaptive feedback to a network connection matrix allows formation of new attractors corresponding to “good” patterns discovered in chaos.
Global Chaos in a Discrete Time-Dependent Complex Ginzburg-Landau Equation
Authors: Otsuka Kenju , Ikeda Kensuke
Published: February 2023

Spatiotemporal behavior of spatially distributed nonequilibrium systems is a crucial problem in complex dynamics. In particular, in high-dimensional chaotic systems, different solutions (spatial structures) coexist in the stationary state. The important fundamental question then arises: What kind of spatiotemporal behavior takes place when coexisting equilibria (patterns) become dynamically unstable? We have investigated this general issue for years, and recently discovered self-induced switching between coexisting attractor ruins by an internally created chaotic force, i.e., chaotic itinerancy, in some high-dimensional chaotic systems including a coupled bistable chain1, multimode Maxwell-Bloch2 and spatially-coupled laser systems.3 The essential common requirements for this phenomenon have been found to be ’coupling’ between elements and ’on-site nonlinearity’. This fact inspired us to investigate a simple model system, the time-dependent Ginzburg-Landau (TDGL) equation system, which includes complex coupling and nonlinearity in a general fashion.4 TDGL has been extensively investigated to understand turbulent phenomena in spatially extended nonequilibrium systems. However, attention has been focused on the behavior around the localized equilibrium, and interplay between coexisting equilibria has been left an open question. In this paper, we discuss a discrete TDGL equation with complex coupling coefficients under the periodic boundary condition, which expresses spatiotemporal dynamics of a one- dimensional looped nonlinear oscillator chain, e.g., lasers. We investigate its spatiotemporal dynamics, paying special attention to the interplay between local chaos around coexisting equilibria and the scenario leading to global chaos, which is expected to result from the connection between local chaotic orbits.
Induced Focusing of Optical Beams in Self-Defocusing Kerr Media
Authors: Agrawal Govind P.
Published: February 2023

A weak optical beam is shown to exhibit induced focusing in a self-defocusing medium as a result of cross-phase modulation imposed on it by a copropagating intense pump beam.
Induced Focusing of Optical Beams in Self-Defocusing Kerr Media
Authors: Agrawal Govind P.
Published: February 2023

Self-focusing is a well-known nonlinear phenomenon. In a Kerr medium in which the refractive index n varies with intensity I as n=n0+n2I, an optical beam can overcome the natural diverging tendency and become self-focused as a result of the converging wavefront imposed on it by self-phase modulation (SPM). This occurs only for Kerr media for which n2 >0. By contrast, SPM imposes a diveraging wavefront when n2 <0. Optical beams then spread faster than diffraction, and are said to be self-defocused. In this paper we show that an optical beam can be focused even in a self-defocusing medium if it propagates together with an intense pump beam that itself experiences self-defocusing. We refer to this phenomenon as induced focusing. The physical mechanism behind induced focusing is cross-phase modulation (XPM), a nonlinear effect through which the phase of an optical beam is affected by other copropagating beams. Even though such a coupling does not lead to an energy transfer, it can redistribute the energy within each beam. In general, the XPM-induced coupling reshapes the beam profile through transverse modulation instability.1 It can lead to induced focusing under certain conditions discussed below. Induced focusing can also occur in a self-focusing medium.2
Stationary Transverse Field Patterns of an Optically Pumped Ring Laser
Authors: Tamm Chr.
Published: February 2023

We report experimental observations on the formation of stationary transverse patterns of the optical field in an optically pumped traveling-wave laser. The active medium of the laser is sodium dimer (Na2) vapor. The field patterns arise from the superposition of phase-locked higher-order transverse optical modes of the laser resonator. The astigmatically compensated ring resonator of the laser has the transverse-mode structure of a cylindrically symmetric, semi-confocal cavity. The narrow gain linewidth of the active medium permits to selectively excite groups of frequency-degenerate transverse resonator modes of common order. The shapes of the emitted field patterns are in agreement with the predictions of Brambilla et. al. (1990 NDOS conference, Afton, Oklahoma, paper ThB3).
Dynamics and Transverse Effects in Nonlinear Planar Resonators: A Unified Modal Theory
Authors: Haelterman M. , Vitrant G.
Published: February 2023

In a recent paper, we proposed a new theoretical model of nonlinear optical cavities1. Our theory, which is valid for both nonlinear (NL) waveguide couplers and NL Fabry-Pérot (FP) with arbitrary angle of incidence, constitutes a unified theory of nonlinear planar resonators. The main advantage of the model is that it greatly simplifies the numerical study of transverse effects in NL resonators and provides a deep understanding of physical phenomena related to Optical Bistability (OB) in such devices. In particular it allowed us to analyse the role of diffraction and the influence of the incident angle on the steady-state NLFP response1,2.
Laser Cooling with Squeezed Light.
Authors: Shevy Y.
Published: February 2023

The process of laser cooling in a quasi resonant standing laser wave is one of the principal technics of laser cooling of atoms. Recent advances in this field include breaking both the "Doppler and the recoil limits". On another front modification of the quantum statistical properties of the "vacuum" fluctuations by squeezing has been achieved in the laboratory. It is, therefore, interesting to find what is the nature of the modification of the laser cooling process when the atoms are also embedded in squeezed vacuum. Such a state can be produced in principle by a degenerate parametric amplifier whose input are vacuum fluctuations. It is shown that due to the modified decay rates of an atom which is embedded in such a state, profound modification of the cooling processes in a standing wave is achieved . Among the important results obtained is the change of sign of the stimulated force from a heating force in normal vacuum to a cooling force in squeezed vacuum. This phenomenon can result in cooling forces more than two orders of magnitude larger than the maximum force in normal vacuum. In this talk the method for calculating the force in squeezed vacuum will be given. The modified force will be compared to the force in normal vacuum and finally the practical implications of these results for laser cooling will be discussed.
Nonlinear Stochastic Dynamics of Semiconductor Laser Gain Switching
Authors: Mecozzi A. , Sapia A. , Spano P.
Published: February 2023

A particular structure of the intensity fluctuations during semiconductor laser gain switching is experimentally found. This new effect is due to the field-carriers interaction inside the laser cavity.
Dynamic Optical Bistabilities in ZnSe/ZnS Multiple Quantum Wells
Authors: Liu Yudong , Yang Xiangming , Li Chunfei , Shen Dezhen , Fan Xiwu , Fan Guanghan , Chen Lianchun
Published: February 2023

The excitonic optical nonlinearities in II-VI semiconductor thin films and multiple quantum wells (MQWs) are much complicated than those of GaAs MQWs because the wider band gap and smaller excitons of II-VI semiconductor materials. We report here the observations of dynamic optical bistabilities in ZnSe/ZnS MQWs at low temperature caused by excitonic optical nonlinearity.
High-Frequency Optical Bistability in Semiconductor Optical Amplifiers
Authors: Mace D A H , Adams M J , Devlin W J
Published: February 2023

Fabry-Perot semiconductor laser amplifiers (FPSLA) have potential applications for optical logic, because they display dispersive optical bistability which can be switched with microwatts of optical powers [1]. However, although the optical transition times are fast, the maximum clock frequency at which the bistability will operate is limited by the carrier recombination time. Consequently methods of reducing this time are important for high-speed logic applications [2]. One suggestion to reduce the recombination time is to operate the device at higher carrier densities, provided lasing action can be suppressed, e.g. by the use of a low-reflectivity coating on the facets [3]. In this paper we show experimentally how reducing the recombination time, by low-reflectivity coating the amplifier, increases the maximum clock frequency.
Radiation-trapping: a new mechanism for chaos in optical systems
Authors: Möller M. , Lange W.
Published: February 2023

Chaos in simple optical systems can be caused by a number of known mechanisms such as time delays or modulated parameters, or by more intrinsic effects like Rabi oscillations - described by the “Laser-Lorenz equations” - or by the light shift in conjunction with an external magnetic field. We show that the effect of radiation trapping, i.e. the reabsorption of fluorescence light, can produce chaos as well.
Neural Network Applications to Optical Chaos
Authors: Pethel S. D. , Bowden C. M. , Sung C. C.
Published: February 2023

Modeling, characterization and prediction with regard to chaotic systems has been an area of vigorous pursuit for many years. Linear methods, such as Fourier decomposition, do not distinguish chaotic dynamical behavior from noise. Of fundamental importance is the characterization of the physical system or the underlying equations from a given time series or phase space attractor, as well as the influence of noise in coupling across basin boundaries and modifications of the otherwise purely deterministic dynamics. Local approximation methods in relation to arbitrary chaotic attractors, in general, are insufficient to deduce the generating equations and conditions.1 A forward-feed, hidden-layer, neural network (FFNN), on the other hand, is manifestly a function generator, and when trained adequately on a chaotic time series, is shown to constitute a global approximation to the attractor.2 That is, a FFNN, trained upon a chaotic time series, becomes a functional realization of that time series, in the global sense. Furthermore, a FFNN is shown to course grain the noise, in a time series during training, in the least-squares sense.3 The functional realization property of the FFNN allows the possibility for data window extension, once it is trained on a stationary time series, which can be, in fact, a rather narrow window. This is accomplished in the FFNN by choosing the input, in the form of delay coordinates, from a portion of the original time series which was not part of the training set, and then feeding the output into the input; thus, the trained FFNN becomes self-generating, and facilitates data window extension.
Instabilities in Lasers with an Injected Delayed-Feedback-Controlled Signal
Authors: Loiko N.A. , Samson A.M.
Published: February 2023

In [1,2] it was shown that control of laser losses or pump by means of delayed feedback (FB) leads to enrichment of the lasing dynamics. Here we present theoretical investigations of a delay effect of the FB forming an injected signal. Both a phase-locked signal and an uncoherent one are considered.
Chaos and Multistability in Bimode CO2 Laser with Saturable Absorber
Authors: Tanii K. , Sugawara T. , Tachikawa M. , Hong F.-L. , Tohei T. , Shimizu T.
Published: February 2023

Recently, instabilities and chaos in a single-mode CO2 laser with a saturable absorber (LSA) have attracted much attention as a direct access to nonlinear dynamics, such as Shil'nikov chaos and Feigenbaum's period-doubling scenario [1,2]. Introduction of extra lasing modes may bring novel aspects into the laser dynamics and largely extend applicability of the LSA as a model of dynamical systems.
Experimental Control of a Chaotic Laser System
Authors: Roy Rajarshi , Murphy T.W. , Maier T.D. , Gills Zelda , Hunt E.R.
Published: February 2023

The exploitation of chaotic and nonlinear dynamical phenomena for practical applications has recently been transformed from concept to reality. Two major approaches to achieving control of chaotic systems have been developed. Hubler and his coworkers have studied control algorithms for driven nonlinear systems where the time dependence of the driving forces necessary to to obtain resonant stimulation are computed from Poincare maps of the system or from detailed mathematical models.1 A different approach was initiated by Ott Grebogi and Yorke (OGY); they suggested that a chaotic attractor typically has many unstable periodic orbits associated with it, that could be stabilized by appropriate modifications to a system parameter.2 Their approach was experimentally demonstrated by Ditto, Rauseo and Spano in their experiments on a magnetoelastic ribbon.3
Observation of Chaos in Off-Bragg Photorefractive Four-wave Mixing
Authors: Shaw Kenneth D.
Published: February 2023

In the past few years, several authors have reported observations of chaotic behavior in various photorefractive phase conjugators which involve some form of external feedback, either by way of mirrors or reflections from the crystal faces [1]. We have recently observed such behavior, for the first time to our knowledge, in an externally pumped phase conjugate mirror with no such feedback mechanisms. The origin of chaotic behavior in such a system is fundamentally different from that in either of the former two cases. In the case of the phase conjugate resonator, the chaos apparently arises from a competition between different cavity modes, and in the self-pumped phase conjugator from competition between different photorefractive gratings with different time scales, while in the present case where all the beams are externally supplied, the chaotic behavior is the result of time-dependent phase transfer among the four beams [2]. For the particular set of parameters (coupling constant, geometrical factors, etc.) used in our experiments, theory [3] predicts that such unstable behavior will not occur in ordinary photorefractive four-wave mixing. It will be shown, however, that the observed chaotic oscillations in the phase conjugate intensity are the result of enhanced gain which can occur when one of the pumping beams deviates slightly from the Bragg angle for the photorefractive phase grating (off-Bragg four-wave mixing, or OBFWM)[4].
Self and mutual phase conjugation via thin layers
Authors: Zel’dovich B. Ya. , Goosev I. V. , Krivoschekov V. A.
Published: February 2023

Consider a nonlinear optical layer with small thickness L, i.e. with L≪λ/θ2, where θ is the angle between interacting waves. If the nonlinearity is of the phase type, the action of the layer on the transmitted beam is the phase modulation only: (1) where φ(x,y) is connected with the nonlinear action of the intensity distribution of the field, φ = s|E|2. However, the phase modulation produces no extra intensity modulation, and therefore there is no feedback in a thin layer even for a large (|φ| ≫ 1) nonlinearity. This is a strong drawback for such important media as semiconductor quantum wells, for which L<1μm, or liquid crystal cells.
New Types of Switching Waves and Diffractive Autosolitons in Wide-Aperture Nonlinear Interferometers and Lasers
Authors: Fedorov S.V. , Khodova G.V. , Kostritskaya K.S. , Rosanov N.N.
Published: February 2023

We investigate the new types of transverse patterns in wide-aperture passive interferometers and lasers. We propose and analyze equations of motion for a diffractive autosoliton in passive nonlinear interferometers excited by external coherent radiation with gradually non-uniform characteristics. If external radiation wave front does not contain dislocations at the interferometer aperture, autosoliton moves along the steepest descent lines of effective potential expressed by linear combination of the intensity and the phase of radiation incident on the interferometer. With the dislocations, the motion with autosoliton rotation becomes possible. The coupled switching wave and autosoliton structures in bistable and multistable interferometers are studied. The dynamics of autosoliton formation in conditions of transverse field structure instability and in nonlinear interferometer with unstable resonator is considered. The peculiarity of autosolitons in lasers with saturated absorption is a diffractive shift of generation frequency. This aspect being taken into account, positive (bright) and negative (dark) laser autosolitons are demonstrated and autosolitons interaction is investigated.
Dynamic Three-Dimensional Propagation of Light Pulses
Authors: Luther G. G. , Moloney J. V. , Hart D. E. , Wright E. M.
Published: February 2023

In this paper we illustrate several characteristics of dynamic three-dimensional nonlinear propagation of light pulses. Recent work has shown that the fully spatio-temporal propagation of a light wave envelope in a cubically nonlinear medium displays, in addition to the usual transverse structures, longitudinal dynamics which play an essential role in the evolution of the wave [1, 2, 3]. It has been suggested that the effect of dispersion coupled with self focusing causes short light pulses having beam waists much larger than their pulse length to display spectral characteristics typical of experimental observations of supercontinuum generation [1]. A recent computational effort has illustrated that the presence of dispersion can inhibit collapse due to two dimensional self focusing in normally dispersive media causing structure in the propagation direction as well as the transverse direction [3]. Finally, analysis of three dimensional propagation of light waves in anomalously dispersive media [4, 5] reveals a set of symmetric solutions which would exist in the intermediate state between collapse and dispersal. The practical stabilization of these light pulses is an open problem.
Phase singularities in a Fabry–Perot resonator with an intra–cavity Nematic Liquid Crystal film
Authors: Kreuzer M. , Neubecker R. , Tschudi T.
Published: February 2023

Formation of transversal patterns and the appearance of phase singularities in nonlinear optical systems have attracted growingly interest in recent years [1, 2]. Up to now, most theoretical and experimental work has been performed for Maxwell–Bloch systems. However, it also turned out that these phenomena can be found in other nonlinear optical feedback configurations as well. Even if the system presented in this paper has in some aspects ’exotic’ properties (compared to Maxwell–Bloch models), it nevertheless shows similar pattern formation with broken symmetry [3, 4, 5]. We now present the first experimental evidence of phase singularities in the intracavity wave.
Laser rate equations with phase-sensitive interactions
Authors: Etrich C. , Mandel Paul , Otsuka Kenju
Published: February 2023

We derive the following set of equations describing a two-mode semiconductor laser for the case of a Fabry-Perot configuration, taking into account the holes burned into the amplifying medium by the standing field pattern and phase-sensitive interactions: (1) where κ = κ2/κ1 is the ratio of the decay rates of the electric fields E1 and E2. It is fixed to be larger than unity.
Simple Modeling of Feedback-Induced properties in Semiconductor Lasers
Authors: Meziane B. , Besnard P. , Stephan G.
Published: February 2023

The effects of an external optical feedback on semiconductor laser properties have long been a subject of considerable interest[1-7], and continue to attract growing attention among various scientific groups. Such an interest is in great part due to the wealth of reported observations, and the lack of a definite interface between theories, which do not always corroborate, and experiments. For example, based on their experimental data, some authors have suggested that the semiconductor laser with optical feedback could be a good candidate for the observation of optical chaos[2,5,6]. The idea stemmed from the fact that the feedback signal would provide the necessary third degree of freedom which when added to the coupled rate equations would result in a 3D autonomous system (just as in the ’Lorenz’ case of turbulence in fluids) which when the conditions of an instability emergence are fulfilled may give rise to some route towards optical chaos. Precise characterisation of such chaotic behavior however still remains obscure.
Statistics of Topological Defects in Linear and Nonlinear Optics
Authors: Ramazza P.L. , Residori S. , Giacomelli G. , Arecchi F. T.
Published: February 2023

A topological defect of a complex field is a point where the intensity of the field vanishes and the circulation of the phase gradient around it has a value that is an integer (called topological charge) multiple of 2tt. In optics, defects have been theoretically predicted [1,2] and experimentally observed both in linear [3] and in nonlinear [4] systems. Linear experiments consist in scattering coherent light from random diffusers, resulting in a speckle field. We compare the experimental statistical distributions of defects for the linear and the nonlinear case at large F. The nonlinear experiment [4] consists of a ring cavity in which a photorefractive BSO crystal, pumped by an Ar+ laser, acts as a light amplifier via a two-wave mixing mechanism. At small F, where only one mode per time is present in a periodic or chaotic alternation [5], the defects are a trivial signature of the symmetry of that specific mode. On the contrary at high F, where many modes coexist, the defect dynamics reflects the mode competition and have a role in mediating turbulence [6]. For a fixed high Fresnel number we study the fluctuations of the total number of defects in the nonlinear field. We repeat the same measurement in the linear case where the fluctuations are trivially due to a translational motion of the random diffuser. The histograms relative to the nonlinear and linear case are plotted in Fig.1a and 1b together with a Poissonian best fit. In Fig. la we report also the result of a theoretical prediction by Gil et al. [7]. The hypothesis of their work is that defects can only be created and annihilated by pairs, with rates of creation Γ = α and annihilation Γ = βn2 where n is the number of pairs present. This lead to a distribution which is a square Poissonian in the number n of pairs.
Spatial and Temporal Behaviors of Instabilities Generated by Counterpropagating Laser Beams in Rubidium Vapor
Authors: Blouin A. , Pinard M. , Maitre A. , Leite J.R. Rios , Boyd R.W. , Grynberg G.
Published: February 2023

Pattern formation in nonlinear systems is a very active subject in many areas of physics. For example, in hydrodynamics the arrangement of the convective cells of the Rayleigh-Bernard instability [1] constitutes a model problem for pattern formation. In optics, important advances have been recently obtained in the case of lasers [2]. In contrast, transverse pattern formation in mirrorless optical passive systems [3] is no so wellknown because of the intrinsic complexity of a system without cavity and of the fact that the first experiments were done with pulsed lasers [4], We present here results obtained with c.w. lasers and rubidium atoms. In particular, we show some interesting relationship with the hydrodynamics observations.
Solitary Wave Emission in a Planar Waveguide with the Adjoining Linear and Nonlinear Thin Film
Authors: Jeong Jong-Sool , Kwak Chong Hoon , Lee El-Hang
Published: February 2023

The spatial soliton in Kerr-like nonlinear media has been the subject of extensive research because of its potential application to all-optical switching [1]. In particular, spatial solitary waves in nonlinear waveguides are of cunent interest because of a novel, very interesting optical bistable and switching effect [2,3]. The soliton coupler, suggested by Heartley et al., is one of the most exciting examples to utilize the threshold effect of spatial soliton emission for the sharp switching devices [4]. The majority of theoretical work to date, however, has been restricted to the planar waveguides consisting of the linear thin film bounded by one or two nonlinear semi-infinite media [2,3]. In this work, we consider a planar waveguide consisting of the adjoining linear and nonlinear guiding thin film covered by two linear semi-infinite media, as shown in Fig. 1. The waveguide configuration has distinctive features: (i) due to the confinement of the nonlinearity, the emitted nonlinear wave is generally a solitary wave rather than a soliton and (ii) it can control the emitted power of the solitary wave and the hysteresis of the optical bistability by varying the thickness of the nonlinear thin film.
Long-term storage of a soliton bit stream using phase-sensitive amplification
Authors: Mecozzi Antonio , Kath William L. , Kumar Prem , Goedde Christopher G.
Published: February 2023

Recently we have shown that stable soliton-like pulse propagation over ultra-long distances is possible in a nonlinear fiber line in which linear loss is balanced by periodic phase-sensitive (parametric) amplification.1 In such a line the length scale over which pulse evolution occurs is significantly increased beyond a soliton period because of the attenuation of phase variations across the pulse’s profile by the amplifiers. Here we examine the effects of quantum noise in the context of a storage ring for a bit stream of soliton-like pulses. We show that the one’s (soliton pulses) are asymptotically stable and the noise on the zero’s of the bit stream (absence of a soliton) is bounded. Moreover, we present evidence that the soliton-soliton interaction and Raman self-frequency shift are efficiently suppressed by the phase-sensitive amplifiers (PSA’s). The effects of direct timing noise and cubic dispersion in the fiber could also be decreased by using a pulsed pump (gain modulation) for the PSA’s.
Chaotic polarization behavior in second harmonic generation
Authors: Trillo Stefano , Assanto Gaetano
Published: February 2023

The possibility of achieving large phase shift at reasonable powers has revived interest in cascaded quadratic interactions, where a fundamental frequency (FF) field may acquire a nonlinear phase change interacing with the generated second-harmonic (SH) [1]. This effect has been mainly described in the assumption that only a FF and a SH scalar field interact through an effective nonlinearity [2]. Hereby we demonstrate that the onset of spatial chaos poses fundamental limitations to the efficiency of SH generation and to the use of a coherent SH seed in phase sensitive modes of operations [3, 4]. Moreover, we point out that vectorial interactions generalize the cascading effect based on the scalar approach, since two orthogonal FF beams may acquire energy from one another through a process which implies the conversion to the SH field as an intermediate step. When this polarization cascading is exploited for all-optical devices [5, 6], it is crucial to establish the conditions for which the field evolutions remain regular.
Polarisation Modulation Instability in Weakly Birefringent Fibres
Authors: Murdoch S. G. , Leonhardt R. , Harvey J. D.
Published: February 2023

Modulation instability (MI) is a phenomenon exhibited by waves propagating in nonlinear dispersive media, in which weak amplitude perturbations at different frequencies are subject to gain. In the scalar description of wave propagation in optical fibres governed by the nonlinear Schrödinger equation (NLSE), MI can occur only in the anomalous dispersion regime, and this was the first form of MI to be observed [1]. Soon after this observation, however, it was predicted that the coherent interaction of two different circularly polarised waves of the same frequency propagating in a birefringent fibre would give rise to modulation instability in both the normal and the anomalous dispersion regimes [2,3]. To our knowledge this prediction has not been experimentally verified. Modulation instability has however, been observed in the normal dispersion regime by pumping highly birefringent fibres with intense red or green pulses [4,5]. This form of MI arises from the incoherent interaction of two linearly polarised pulses propagating down the fast and slow axes of the fibre simultaneously. In these highly birefringent fibres, the terms which give rise to the coherent MI can be neglected in view of the large wavevector mismatch between the orthogonal modes. We report here the first observation of "polarisation modulation instability" (PMI). This instability possesses different characteristics depending on whether the pump is on the fast or slow axis.
A 1×7 fiber coupler with optically induced grating
Authors: Weinert-Rączka Ewa
Published: February 2023

The interest in multiple core couplers increasing in last few years is connected with their potential applications to the optical fibre networks. One of the common geometries is the 1×7 single-mode fiber coupler, consisted of central core and six identical cores situated on the ring, which exhibits a capability of optical power splitting and a good coupling uniformity [1-4]. The ammount of power switched from the central core to the ring ones depends on the geometry of the device. Power dependent switching between central core and ring cores can be obtained in the 1×7 fiber coupler with Kerr nonlinearity [5].
Reduction of the Stimulated Raman Scattering Threshold due to Rayleigh Scattering and End Reflections
Authors: Forghieri Fabrizio , Chraplyvy A. R. , Tkach R. W.
Published: February 2023

As high power lasers become available in the low-loss wavelength region of the optical fibers, it becomes of increasing interest to understand in detail the onset of the nonlinear effects that limit the amount of continuous wave power that can be launched in the fiber. Stimulated Brillouin scattering (SBS) is the nonlinear effect with lowest threshold [1], but due its narrow gain bandwidth this effect can be easily suppressed by using incoherent sources or by dithering the frequency [2]. Stimulated Raman scattering (SRS) has a threshold of the order of 1 W, but its large bandwidth makes it difficult to counteract, therefore it is in practice the limiting effect whenever high powers have to be transmitted through optical fiber.
Rotating Ring Bright Solitons
Authors: Afanasjev V. V.
Published: February 2023

Optical solitons have been observed experimentally for the first time as temporal solitons in optical fibers and then as spatial solitons — self-trapped beams [1-3]. As the circular-symmetry beam in a Kerr medium is unstable displaying blow-up and collapse, spatial solitons have been observed in bulk media as soliton strips or in planar waveguide geometries.
Cascaded Nonlinear Directional Couplers in AlGaAs
Authors: Aitchison J. S. , Villeneuve A. , Stegeman G. I.
Published: February 2023

There is a growing interest in the use of ultrafast, nonlinear optical devices as potential signal processing elements in future telecommunications systems. One of the most promising materials for such devices is AlGaAs, operated at half the band gap. To date a number of integrated, nonlinear, all-optical switching devices have been demonstrated, for example, directional couplers[1], Mach-Zehnder interferometers[2] and X-junctions[3]. However, the experimental results reported have concentrated on single nonlinear elements. In order to make practical nonlinear elements, for information switching and signal processing, a number of devices must be connected in series to perform different tasks. In this submission we report on the first experimental observation of switching in two cascaded directional couplers.
Spatial Solitons Caused by Cascaded Second-Order Nonlinearity in LiNbO3 Planar Waveguide
Authors: Baek Y. , Schiek R. , Stegeman G. I.
Published: February 2023

Self-trapped optical solitons were proposed from the early days of nonlinear optics and their demonstration based on the third-order nonlinearity have been reported in both the temporal and spatial regimes. 1-3 Recently it has been predicted that a cascaded second-order nonlinearity can produce effects similar to third-order nonlinearities with orders of magnitude higher nonlinear phase shifts. In fact, large nonlinear phase shifts have already been reported.4-5 Presented here is the first demonstration of spatial solitons due to the cascaded second-order nonlinearity.
A Nonlinear Antiresonant GaP/AIP Multilayer Waveguide for Efficient, Surface-Emitted Optical Mixing
Authors: Dai H. , Normandin R. , Delåge A.
Published: February 2023

Surface-emitting nonlinear waveguide devices, based on coherent sum-frequency (SF) mixing of two counter-propagating guided waves, have attracted increasing interest for their potential applications in future high throughput all-optical fiber communication networks. Several authors have recently reported success with the proof-of-concept demonstrations of passive and laser-integrated nonlinear waveguide devices as wavelength sensors for frequency control of DFB lasers.[1], parametric spectrometers for DWDM demultiplexing [2] and serial-to-parallel-convertors for 100Gb/s TDM demultiplexing [3]. From the view point of practical systems implementation, one key parameter for these devices is the overall SF conversion efficiency because it ultimately dictates the signal-to-noise ratio and bit error rate (BER). For devices using quasi-phase-matched (QPM) AlGaAs multilayers structure, the efficiency is further affected by two somewhat related factors: the absorption of the SF light by the waveguide materials and the coupling efficiency of the input signal. Since the band gap of GaAs is smaller than the SF light photon energy for the wavelength that we are interested in, strong absorption occurs as the SF light propagating towards the waveguide surface. On the other hand, for thin guides, large mismatchs between waveguide thickness and fiber core size results large coupling losses. In order to improve the optical coupling, we have recently demonstrated a device employing a nonlinear antiresonant reflecting optical waveguide (NARROW) geometry [4]. The NARROW structure allows large coupling efficiency with fibers by providing a thick guiding core with high modal discrimination. We have obtained coupling efficiency of ~15% from a 8-μm core diameter fiber to a 2.6 μm thick NARROW device. Further improvement in coupling efficiency, however, is limited by the SF light absorption of the thick nonlinear layers.
Surface Emitting Second Harmonic Generation in Poled Polymer Waveguides
Authors: Otomo A. , Stegeman G.I. , Horsthuis W.H.G. , Möhlmann G.R.
Published: February 2023

The mixing of counter propagating guided waves to generate second harmonic radiation normal to the surface was initially demonstrated in Ti in-diffused LiNbO3 waveguides over a decade ago.[1] Although the signals were too small to be useful in practice, several applications were demonstrated or proposed, including picosecond signal processing, [2] picosecond optical transient digitizers,[3] and spectrometers.[4] The device potential of this phenomenon for ultra fast signal processing, waveguide division demultiplexing, etc., has attracted attention recently.[5] Since the signal at the harmonic frequency only traverses the waveguide depth, applications to blue and green light source can be realized by using huge resonant nonlinearities which is over 400pm/V. In the last few years, several works in GaAs based waveguides were reported and the conversion efficiency was improved dramatically by using a form of quasi-phase matching in multi layered structures. On the other hand, organic polymers have also been shown to have great potential for second order nonlinear optical applications because they have large nonlinearities and ease of fabrication. Using very large second order nonlinearities in poled polymers, signals are easily detectable with uncooled CCD arrays on a single shot basis and all the device applications become realistic. Here we discuss surface emitting second harmonic generation (SHG) devices in 4-dimethylamino-4′-nitrostilbene (DANS) side-chain polymers.
Bright temporal solitons in AlGaAs waveguides at 810 nm
Authors: Villeneuve Alain , Dumais Patrick , Morel Alain , Aitchison J. Stewart
Published: February 2023

We report the experimental observation of bright temporal solitons propagating within an AlGaAs waveguide at 810 nm. A gradual narrowing of the output pulsewidth has been measured as a function of input power.
Quasi-Phasematched Second Harmonic Generation in AlGaAs Waveguides Prepared by Wafer-Bonding
Authors: Yoo S. J. B. , Bhat R. , Caneau C. , Koza M. A.
Published: February 2023

Quasi-phasematched SHG is observed in an AlGaAs waveguide epitaxially grown on a template where a periodic domain inversion is achieved by wafer bonding and OMCVD regrowth.
Squeezed Vacuum Generation using a Quasiphasematched LiNbO3 Waveguide Parametric Amplifier
Authors: Serkland D.K. , Fejer M.M. , Byer R.L. , Yamamoto Y.
Published: February 2023

We have measured phase-sensitive amplification and quadrature squeezing using a quasiphasematched LiNbO3 waveguide degenerate parametric amplifier. We observed a 14% reduction in the noise in one quadrature, compared to the vacuum state, which is in quantitative agreement with our phase-sensitive amplification measurements.
Exact soliton solutions of the cubic-quintic complex Ginzburg-Landau equation
Authors: Akhmediev N. , Afanasjev V. V. , Soto-Crespo J. M.
Published: February 2023

Soliton solutions of the 1-D complex Ginzburg-Landau equations (CGLE) are analyzed. We apply the same approah to look for stationary solutions of both the cubic and quintic CGLE, and fing general solutions in both cases. We reveal the singularities of the general solutions and find some families of special solutions which exist at those values of the coefficients where the general solutions cannot be applied. The stability of the special solutions is investigated numerically.