Pattern formation by kicked solitons in the two-dimensionnal Ginzburg-Landau medium with a transverse grating

We consider the kick-induced mobility of two-dimensional (2D) fundamental dissipative solitons in models of lasing media based on the 2D complex Ginzburg-Landau (CGL) equation including a spatially periodic potential (transverse grating). The depinning threshold is identified by means of systematic simulations, and described by means of an analytical approximation, depending on the orientation of the kick. Various pattern-formation scenarios are found above the threshold. Most typically, the soliton, hopping between potential cells, leaves arrayed patterns of different sizes in its wake. In the laser cavity, this effect may be used as a mechanism for selective pattern formation controlled by the tilt of the seed beam. Freely moving solitons feature two distinct values of the established velocity. Elastic and inelastic collisions between free solitons and pinned arrayed patterns are studied too.Comment: 15 pages, 20 figures (with 41 sub-figures

The theory of photorefractive resonance for localized beams in two-carrier photorefractive systems

This paper extends the existing theory of two carrier photorefractivity resonance, which is generally applied to Iron doped Indium Phosphide (InP:Fe), to the case of low non-harmonic illumination. The space charge field profile is computed, and the variations of its amplitude, width and position are determined as functions of the background intensity. The effect of photorefractive resonance on these quantities is evidenced, contributing to the understanding of published experimental results in InP:Fe.Comment: Physical Review A: Atomic, Molecular and Optical Physics Accepted (2009) To be publishe

Stabilization of vortex beams in Kerr media by nonlinear absorption

We elaborate a new solution for the problem of stable propagation of transversely localized vortex beams in homogeneous optical media with self-focusing Kerr nonlinearity. Stationary nonlinear Bessel-vortex states are stabilized against azimuthal breakup and collapse by multiphoton absorption, while the respective power loss is offset by the radial influx of the power from an intrinsic reservoir. A linear stability analysis and direct numerical simulations reveal a region of stability of these vortices. Beams with multiple vorticities have their stability regions too. These beams can then form robust tubular filaments in transparent dielectrics as common as air, water and optical glasses at sufficiently high intensities. We also show that the tubular, rotating and speckle-like filamentation regimes, previously observed in experiments with axicon-generated Bessel beams, can be explained as manifestations of the stability or instability of a specific nonlinear Bessel-vortex state, which is fully identified.Comment: Physical Review A, in press, 9 pages, 6 figure

Ultrashort light bullets described by the two-dimensional sine-Gordon equation

By using a reductive perturbation technique applied to a two-level model, this study puts forward a generic two-dimensional sine-Gordon evolution equation governing the propagation of femtosecond spatiotemporal optical solitons in Kerr media beyond the slowly varying envelope approximation. Direct numerical simulations show that, in contrast to the long-wave approximation, no collapse occurs, and that robust (2+1)-dimensional ultrashort light bullets may form from adequately chosen few-cycle input spatiotemporal wave forms. In contrast to the case of quadratic nonlinearity, the light bullets oscillate in both space and time and are therefore not steady-state lumps

Fast build up of photorefractive spatial solitons in iron doped indium phosphide

Conférence OralInternational audiencePhotorefractive (PR) spatial soliton propagation hints that all optical routing can be achieved through soliton interactions. This requires, however, fast build up and sensitivity to telecommunication wavelengths. We have investigated the build up of infrared (1,06m) photorefractive solitons in iron doped indium phosphide (InP:Fe) and shown that PR self focusing occurs at input powers of hundreds of W and intensities in the range of W/cm2, showing a build up time down to the microsecond

Stable nonlinear vortices in self-focusing Kerr media with nonlinear absorption

We have studied the stability properties of nonlinear Bessel vortices in self-focusing Kerr media with nonlinear absorption. Nonlinear Bessel vortices are propagation-invariant solutions of the nonlinear Schrödinger equation with cubic nonlinearity and nonlinear absorption. We have found that these vortices can be stable against perturbations, including the azimuthal perturbations that usually break the cylindrical symmetry of standard vortex solitons in self-focusing Kerr media. This property is seen to arise from the stabilizing effect of nonlinear absorption. Our model is the nonlinear Schrödinger equatio

Filtre SIW d'ordre 6 en bande C avec un couplage croisé. Analyse expérimentale du comportement thermique.

National audienceCet article présente un filtre SIW (Substrate Integrated Waveguide) d'ordre 6 en bande C réalisé sur un substrat d'alumine de permittivité 9.9. Un couplage croisé entre résonateurs non-adjacents est introduit afin d'améliorer les réjections; une contrainte indispensable pour les applications spatiales. La compatibilité avec les circuits planaires est assurée par l'intermédiaire d'une transition microruban spécifique. Des tests en température ont été réalisés afin d'évaluer le comportement du filtre dans un environnement spatial. Les résultats expérimentaux sont en accord avec les simulations

West Nile Virus in Morocco, 2003

West Nile virus (WNV) reemerged in Morocco in September 2003, causing an equine outbreak. A WNV strain isolated from a brain biopsy was completely sequenced. On the basis of phylogenetic analyses, Moroccan WNV strains isolated during the 1996 and 2003 outbreaks were closely related to other strains responsible for equine outbreaks in the western Mediterranean basin