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Instabilités spatiales en milieu de Kerr : réseaux de solitons spatiaux et brisure de symétrie des solitons multimodes dans un guide plan

Abstract : This thesis dealt with a theoretical and experimental study of spatial transverse instabilities arising from the nonlinear interaction of coherent electromagnetic waves with a homogeneous and isotropic Kerr medium in a planar-waveguide configuration — i.e. a transversally one-dimensional configuration or (1+1)D. The goal of this work was to improve the understanding of those phenomena related to solitonic propagation of light in Kerr media. Furthermore, our research is also in line with applied purposes, the high potential of such self-induced and reconfigurable waveguides being great in all-optical and ultrafast signal processing. The major part of our work has been devoted to the process of spatial modulation instability in picosecond pulsed regime. Intrinsically linked to a nonlinear variation of the index of refraction via the optical Kerr effect, this instability can be brought under control in planar-waveguide geometry, thus creating periodic arrays of optically controllable soliton-like beams. Each soliton of the array constitutes a dynamic and self-induced graded-index waveguide. This work dealt both with the generation and the stabilization of such arrays, in view to applications in all-optical and ultrafast parallel information processing. A phenomenological study of spontaneous (arising from the spatial noise superimposed to the incident wave) or induced (from a low-contrast interference pattern) modulation instability has been realized with a planar waveguide of carbon disulfide (CS2) at a 532-nm wavelength. We have shown for the first time to our knowledge the generation and control of arrays of spatial solitons, the stability of which, both transversally and upon propagation, was ensured by the temporal relaxation of molecular reorientation that is responsible for the optical Kerr effect in CS2. Moreover, this inertia of the nonlinear response causes a novel spatiotemporal dynamic, which is responsible for the appearance of a spatially-interleaved secondary array during the pulse duration. A few applications of such soliton arrays, like multiple waveguiding or routing, have finally been discussed. The second part of this thesis was driven in collaboration with the Service d'optique et acoustique from the université libre de Bruxelles. Using a particular arrangement of polarization and individual profiles of a pair of soliton beams, we have demonstrated for the first time experimentally, the propagation of a bound state of such solitons along with its sharp and random symmetry-breaking instability. This instability originates from the strong cross-phase modulation experienced by the soliton pair in the CS2 waveguide and was initiated by noise fluctuations of the laser source used in the experiment. Beyond the universal character of such instability, this preliminary study opens up the way to a possible application to all-optical and ultrafast switching at an arbitrary low power of command.
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https://tel.archives-ouvertes.fr/tel-00008017
Contributor : Cyril Cambournac <>
Submitted on : Wednesday, January 12, 2005 - 9:59:01 AM
Last modification on : Friday, January 15, 2021 - 3:20:42 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:17:12 PM

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  • HAL Id : tel-00008017, version 1

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Cyril Cambournac. Instabilités spatiales en milieu de Kerr : réseaux de solitons spatiaux et brisure de symétrie des solitons multimodes dans un guide plan. Physique [physics]. Université de Franche-Comté, 2003. Français. ⟨tel-00008017⟩

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