Features of the extreme events observed in the all-solid state laser with a saturable absorber

Extreme events (sometimes also called optical rogue waves), in the form of pulses of extraordinary intensity, are easily observed in its chaotic regime if the Fresnel number of the cavity is high. This result suggests that the nonlinear interaction among transverse modes is an essential ingredient in the formation of extreme events in this type of lasers, but there is no theoretical description of the phenomenon yet. We report here a set of experimental results on the regularities of these extreme events, to provide a basis for the development of such a description. Among these results, we point out here: i) the decay of the correlation across the transversal section of the laser beam, and ii) the appearance of extreme events even if the time elapsed since the previous pulse is relatively short (in terms of the average inter-pulse separation), what indicates the existence of some unknown mechanism of energy storage. We hypothesize that this mechanism is related with the imperfect depletion of the gain by some of the transversal modes. We also present evidence in support of this hypothesis.Comment: 9 pages, 9 figure

Influence of a Modulated Parameter on Hantavirus Infection

We study the dynamical behavior of a model commonly used to describe the infection of mice due to hantavirus (and, therefore, its possibility of propagation into human populations) when a parameter is changed in time. In particular, we study the situation when the ecological conditions (e.g., climate benignity, food availability, and so on) change periodically in time. We show that the density of infected mice increases abruptly as the parameter crosses a critical value. We correlate such a situation with the observed sudden outbreaks of hantavirus. Finally, we discuss the possibility of preventing a hantavirus epidemic.Fil: Torre, Maria Susana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física Arroyo Seco; ArgentinaFil: Acquaviva, Anaïs. Université de la Nouvelle Calédonie; FranciaFil: Boyer, Jean-Marc. Université de la Nouvelle Calédonie; FranciaFil: Tredicce, Jorge Raul. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Temporal dynamics of semiconductor lasers with optical feedback

We measure the temporal evolution of the intensity of an edge emitting semiconductor laser with delayed optical feedback for time spans ranging from 4.5 to 65 ns with a time resolution from 16 to 230 ps, respectively. Spectrally resolved streak camera measurements show that the fast pulsing of the total intensity is a consequence of the time delay and multimode operation of the laser. We experimentally observe that the instabilities at low frequency are generated by the interaction among different modes of the laser.We acknowledge support of the European Community TMR program, the NSF Optoelectronic Computing System Center, the NSF (ECS 95-02888), CICYT Project No. TIC95-0563, and DGICYT Project No. SAB95-0674.Peer Reviewe

Deterministic optical rogue waves

Experimental observations of rare giant pulses or rogue waves were done in the output intensity of an optically injected semiconductor laser. The long-tailed probability distribution function of the pulse amplitude displays clear non-Gaussian features that confirm the rogue wave character of the intensity pulsations. Simulations of a simple rate equation model show good qualitative agreement with the experiments and provide a framework for understanding the observed extreme amplitude events as the result of a deterministic nonlinear process.Peer ReviewedPostprint (published version

Spatial structure of broad-area vertical-cavity regenerative amplifiers

We investigate the spatial structure of broad-area vertical-cavity regenerative amplifiers injected with a homogeneous beam. The emerging patterns have a predominantly sixfold rotational symmetry, verifying the recent prediction of formation of hexagons. The length scale is controllable by means of detuning and follows the prediction for tilted waves.Peer reviewe

Les solitons de cavité (étude expérimentale)

L étude expérimentale des structures spatiales localisées indépendantes et contrôlables nommées solitons de cavité dans une cavité semi-conductrice, constitue le cadre du travail présenté dans ce mémoire. Cette étude qui repose sur une expérience d injection optique dans le plan transverse d un laser semi-conducteur à cavité verticale (VCSEL), nous a permis de définir les régions de paramètres où ces structures existent, ainsi que les différentes caractéristiques de leur allumage aussi bien spontané que contrôlé. La possibilité de définir leurs positions ainsi que celle de les mouvoir en utilisant un faisceau d injection composé de franges d interférences ou possédant un gradient de phase, a aussi été démontrée. Dans le but de pouvoir contrôler le transitoire de ces structures, une étude sur celui des lasers de classe B a été réalisée. La suppression du pic de surintensité, des oscillations de relaxations et la réduction du temps de retard présent lors de ce transitoire ont été réalisées de manière expérimentale, en utilisant une technique basée sur la connaissance de l espace de phase de ces lasers.The experimental study of independent and controllable spatially localized structures ( cavity solitons ) in a semiconductor cavity constitutes the body of work presented in this thesis. This study, based on optical injection in the transverse plane of vertical cavity semiconductor laser (VCSEL), has permitted us to define the regions in parameter space where these structures exist. We have also determined the different characteristics of their spontaneous as well as controlled switch-on. In addition, we have demonstrated the feasibility of defining their positions as well as moving them by using an injection beam composed of interference fringes or having a phase gradient. With the goal of controlling the transients of these structures, we have studied transient effects in class B lasers. By exploiting our knowledge of the phase space of these lasers, we studied experimentally the suppression of the overshoot peak, relaxation oscillations and the reduction of the retardation time present in these transients.NICE-BU Sciences (060882101) / SudocSudocFranceF

Powerful radiation propagation in nonlinear structures with periodically modulated index of refraction

NICE-BU Sciences (060882101) / SudocSudocFranceF