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              In systems through which flows of energy or matter propagate, it is possible to observe self-organization phenomena. The system can leave its thermodynamical equilibrium state. Its components self-organize themselves in « dissipative structures », also called « patterns ». In optics, we observe such patterns in the transverse dimensions of laser beams during their propagation in certain nonlinear materials.This thesis aims to study the patterns observed in a photorefractive single feedback system. The forward beam and the beam reflected by the mirror interfere in the photorefractive crystal and modify its electro-optical properties. This modification influences in return the propagation of the beams. If the incident beam is sufficiently powerful, the system reaches the « modulation instability » threshold : the observation of the backward beam reveals that the intensity has self-organized in patterns.Particularly, we deal in depth with two axes of research. Firstly, we study the influence of an orbital angular momentum of the input beam (therefore called a « vortex » beam) on the pattern formation process. This property influences the self-organization phenomenon and the dynamics of the transverse structures. Moreover the results provided by a numerical model of the wave mixing process are in a good accordance with the experimental observations. Secondly, we study the highly nonlinear regime obtained with a classical gaussian pump but very powerful. We show by a statistical analysis that the turbulent state far from the instability threshold contains some extreme events, also called « rogue waves ».
            """ ;
    dct:identifier "NNT: 2013SUPL0020" ;
    dct:issued "2026-05-05T20:56:57.706276"^^xsd:dateTime ;
    dct:language "fr" ;
    dct:modified "2026-05-05T20:56:57.706281"^^xsd:dateTime ;
    dct:publisher <https://rec.harvest-normandie.data4citizen.com/organization/cce9db95-46d9-4dc2-84b6-764215d0a002> ;
    dct:title "Dynamics of optical patterns in a photorefractive system" ;
    dcat:contactPoint [ a vcard:Organization ;
            vcard:fn "CCSD" ] ;
    dcat:distribution <https://rec.harvest-normandie.data4citizen.com/dataset/oai-hal-tel-00965596v1/resource/6c08f7db-7ad2-40ca-9cd6-736507c95fc1> ;
    dcat:keyword "auto-organisation",
        "feedback-system",
        "infoeu-reposemanticsdoctoralthesis",
        "nonlinear-optics",
        "optical-vortex",
        "optique-nonlineaire",
        "rogue-waves",
        "self-organization",
        "spiotherengineering-sciences-physicsother",
        "systeme-a-retroaction",
        "theses",
        "vagues-scelerates",
        "vortex-optique" ;
    dcat:landingPage <https://theses.hal.science/tel-00965596> .

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    dct:issued "2026-05-05T20:56:57.718427"^^xsd:dateTime ;
    dct:modified "2026-05-05T20:56:57.689534"^^xsd:dateTime ;
    dct:title "Dynamics of optical patterns in a photorefractive system" ;
    dcat:accessURL <https://theses.hal.science/tel-00965596> .

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