Self-Pulsating Semiconductor Lasers: Theory and Experiment

We report detailed measurements of the pump-current dependency of the self-pulsating frequency of semiconductor CD lasers. A distinct kink in this dependence is found and explained using rate-equation model. The kink denotes a transition between a region where the self-pulsations are weakly sustained relaxation oscillations and a region where Q-switching takes place. Simulations show that spontaneous emission noise plays a crucial role for the cross-over.Comment: Revtex, 16 pages, 7 figure

Transverse Patterns in Nonlinear Optical Resonators

The book is devoted to the formation and dynamics of localized structures (vortices, solitons) and extended patterns (stripes, hexagons, tilted waves) in nonlinear optical resonators such as lasers, optical parametric oscillators, and photorefractive oscillators. The theoretical analysis is performed by deriving order parameter equations, and also through numerical integration of microscopic models of the systems under investigation. Experimental observations, and possible technological implementations of transverse optical patterns are also discussed. A comparison with patterns found in other nonlinear systems, i.e. chemical, biological, and hydrodynamical systems, is given. This article contains the table of contents and the introductory chapter of the book.Comment: 37 pages, 14 figures. Table of contents and introductory chapter of the boo

Hysteresis of periodic and chaotic passive q-switching self-pulsation in a molecular laser model, and the stark effect as a codimension-2 parameter

We give a systematic comparison of a molecular model for a CO2 laser with a fast saturable absorber and a reduced version of this model. Overall, we find that there is good agreement between these models. We use numerical continuation algorithms to analyze the bifurcation structure of the equations, and complement the results by numerical simulations to model possible experiments. Our study predicts the existence of isolas of periodic passive Q-switching self-pulsations and a rich structure of Q-intervals of stability for these periodic orbits, where Q represents the incoherent pump of the laser. These intervals correspond to the observed phenomenon known as period-adding cascades. Computed loci of codimension-1 bifurcations show that a small shift of a secondary parameter in the reduced model with respect to that of the complete model substantially improves their quantitative agreement. This parameter is associated with the action of the Stark effect in the absorber. We also discuss a necessary condition for chaotic windows to arise as Q changes

Isolas of periodic passive Q-switching self-pulsations in the three-level:two-level model for a laser with a saturable absorber

We show that a fundamental feature of the three-level:two-level model, used to describe molecular monomode lasers with a saturable absorber, is the existence of isolas of periodic passive Q-switching (PQS) self-pulsations. A common feature of these closed families of periodic solutions is that they contain regions of stability of the PQS self-pulsation bordered by period-doubling and fold bifurcations, when the control parameter is either the incoherent external pump or the cavity frequency detuning. These findings unveil the fundamental solution structure that is at the origin of the phenomenon known as “period-adding cascades” in our system. Using numerical continuation techniques we determine these isolas systematically, as well as the changes they undergo as secondary parameters are varied

Physics and Applications of Laser Diode Chaos

An overview of chaos in laser diodes is provided which surveys experimental achievements in the area and explains the theory behind the phenomenon. The fundamental physics underpinning this behaviour and also the opportunities for harnessing laser diode chaos for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient test-bed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified.Comment: Published in Nature Photonic

Réponse excitable et propriétés neuromimétiques de micropiliers lasers à absorbant saturable

Excitability is a well known property of biological neurons. In excitable systems, the response to a perturbation above the excitable threshold is of all-or-none type. Other properties exist in neurons such as the refractory periods and temporal or spatial summation of input stimuli.Excitability has been demonstrated in many III-V semiconductor material devices. Thanks to their nonlinear properties it could be possible to realize neuromimetic and all-optical signal processing with high speed and low energy consumption. Thanks to progress in fabrication techniques it is possible to fabricate high quality micropillar laser with saturable absorber. Thus, using micropillars it could be possible to realize neural photonic networks analog to neural networks.In this thesis work, I studied neuron-like properties of a micropillar laser with a saturable absorber. My main results are : 1) fabrication of micropillars has been improved leading to an increase of their robustness and a reduction of the laser threshold. 2) well known properties of biological neurons, such as excitability, existence of refractory periods, temporal summation, have been demonstrated experimentally and have been numerically analyzed with the Yamada model. 3) propagation effects of excitations have been demonstrated in one-dimensional structures : wire lasers and chains of coupled micropillars.The demonstration of neuromimetic properties in micropillar lasers with saturable absorber and the evidence of propagation of excitations pave the way to neuromorphic networks based on coupled micropillars for neuromimetic signal processing like information encoding with excitable pulses and realization of optical memories.L'excitabilité est une propriété bien connue des neurones biologiques. Il s'agit d'une réponse de type tout-ou-rien à une perturbation au delà d'un seuil caractéristique appelé seuil excitable. D'autres propriétés importantes existent dans les neurones comme les périodes réfractaires et la sommation temporelle ou spatiale de stimuli d'entrée.L'excitabilité a été étudiée dans certains composants actifs à semiconducteur et notamment les composants à semiconducteurs III-V. Leurs propriétés neuro-mimétiques pourraient permettre de traiter l'information de façon tout-optique avec une grande bande passante et une faible consommation.Grâce aux nouvelles techniques de micro-nano fabrication, il est devenu possible de fabriquer des micropiliers lasers à absorbant saturable. Ces micropiliers pourraient permettre la réalisation de réseaux de micropiliers couplés excitables analogues à des réseaux de neurones photoniques.Dans cette thèse j'ai étudié les propriétés neuro-mimétiques de micropiliers lasers à absorbant saturable intégré. Les principaux résultats de cette thèse sont les suivants : 1) la technique de fabrication des micropiliers a été améliorée conduisant à une augmentation de leur durée de vie et une diminution du seuil laser. 2) des propriétés de base des neurones biologiques, comme l'excitabilité, l'existence des périodes réfractaires, la sommation temporelle, ont été mises en évidence expérimentalement et analysées à l'aide du modèle de Yamada. 3) des effets de propagation d'excitations ont été démontrés dans des structures unidimensionnelles : des lasers ligne et des chaînes de micropiliers couplés.La démonstration des propriétés neuromimétiques de micropiliers lasers à absorbant saturable et la mise en évidence de la propagation d'excitations ouvrent la voie à la réalisation de réseaux de micropiliers couplés pour les traitements neuromimétiques des signaux qui pourront être exploités pour de la logique codée à l'aide de pics excitables ainsi que pour du stockage d'information dans des circuits mémoires tout-optiques

Universality in modelling non-equilibrium pattern formation in polariton condensates

The key to understanding the universal behaviour of systems driven away from equilibrium lies in the common description obtained when particular microscopic models are reduced to order parameter equations. Universal order parameter equations written for complex matter fields are widely used to describe systems as different as Bose-Einstein condensates of ultra cold atomic gases, thermal convection, nematic liquid crystals, lasers and other nonlinear systems. Exciton-polariton condensates recently realised in semiconductor microcavities are pattern forming systems that lie somewhere between equilibrium Bose-Einstein condensates and lasers. Because of the imperfect confinement of the photon component, exciton-polaritons have a finite lifetime, and have to be continuously re-populated. As photon confinement improves, the system more closely approximates an equilibrium system. In this chapter we review a number of universal equations which describe various regimes of the dynamics of exciton-polariton condensates: the Gross-Pitaevskii equation, which models weakly interacting equilibrium condensates, the complex Ginsburg-Landau equation---the universal equation that describes the behaviour of systems in the vicinity of a symmetry--breaking instability, and the complex Swift-Hohenberg equation that in comparison with the complex Ginsburg-Landau equation contains additional nonlocal terms responsible for spacial mode selection. All these equations can be derived asymptotically from a generic laser model given by Maxwell-Bloch equations. Such an universal framework allows the unified treatment of various systems and continuously cross from one system to another. We discuss the relevance of these equations, and their consequences for pattern formation.Comment: 19 pages; Chapter to appear in Springer&Verlag book on "Quantum Fluids: hot-topics and new trends" eds. A. Bramati and M. Modugn

Modelling multimode dynamics of semiconductor ring lasers

In this thesis, a modal decomposition method and a time-frequency-domain formalism for the analysis of multimode dynamics of semiconductor ring laser are developed. The diffusion coefficient is suggested as a crucial parameter to take into account. The directional switching dynamics and dependence on the operation parameters has been studied. The lasing wavelength switching accompanied by directional flipping have also been studied. In this framework, a prior selection of the lasing mode is seen as a key factor for the numerical results

Laser Systems for Applications

This book addresses topics related to various laser systems intended for the applications in science and various industries. Some of them are very recent achievements in laser physics (e.g. laser pulse cleaning), while others face their renaissance in industrial applications (e.g. CO2 lasers). This book has been divided into four different sections: (1) Laser and terahertz sources, (2) Laser beam manipulation, (3) Intense pulse propagation phenomena, and (4) Metrology. The book addresses such topics like: Q-switching, mode-locking, various laser systems, terahertz source driven by lasers, micro-lasers, fiber lasers, pulse and beam shaping techniques, pulse contrast metrology, and improvement techniques. This book is a great starting point for newcomers to laser physics