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Theses

Laser à fibre multimode avec remise en forme de faisceau par diffusion Brillouin stimulée

Abstract : Lots of efforts are actually made to develop fiber laser sources to address a variety of applications in science or industry. Thanks to an excellent thermal dissipation ability due to its intrinsic properties, doped fiber can handle high average power. However, the light confinement in the fiber core as well as the interaction lengths give rise to nonlinear effects as stimulated Brillouin scattering (SBS) in the case of a laser with a narrow spectral width. The purpose of this PhD work is to develop a high energy fiber laser source with both a good spatial beam quality and a narrow spectral width in order to be used in coherent LIDAR applications. The approach followed has consisted in fist obtaining the energy and then work ob the beam quality. Thanks to an amplification chain, the last stage being constituted of a multimode Erbium-Ytterbium co-doped fiber, 1,5 μm laser pulses with an energy of more than 1 mJ has been obtained. The very large fiber core avoid the apparition of SBS but the transverse profile of the beam is highly multimode. To recover a good beam quality, a nonlinear reshaping stage has been introduced, using the beam cleanup property of Brillouin effect in a graded index multimode fiber. Moreover, an original scheme of Brillouin amplification has been proposed and studied to maintain the spectral purity of the source.
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  • HAL Id : tel-00864743, version 1

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Bastien Steinhausser. Laser à fibre multimode avec remise en forme de faisceau par diffusion Brillouin stimulée. Optique [physics.optics]. Université Paris Sud - Paris XI, 2009. Français. ⟨tel-00864743⟩

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