Dynamics of optical patterns in a photorefractive system
type: Dataset
description: 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 ».
identifier: NNT: 2013SUPL0020
issued: 2026-05-05T20:56:57.706276
language: fr
modified: 2026-05-05T20:56:57.706281
contact point: Organization
  fn: CCSD
keyword: auto-organisation
keyword: feedback-system
keyword: infoeu-reposemanticsdoctoralthesis
keyword: nonlinear-optics
keyword: optical-vortex
keyword: optique-nonlineaire
keyword: rogue-waves
keyword: self-organization
keyword: spiotherengineering-sciences-physicsother
keyword: systeme-a-retroaction
keyword: theses
keyword: vagues-scelerates
keyword: vortex-optique
landing page: https://theses.hal.science/tel-00965596

Dynamics of optical patterns in a photorefractive system
type: Distribution
format: HTML
issued: 2026-05-05T20:56:57.718427
modified: 2026-05-05T20:56:57.689534
access URL: https://theses.hal.science/tel-00965596

test_moissonnage_selune
type: Agent