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Etude du spectre d'émission de lasers à rétroaction répartie dans des couches minces de polymères excités par plusieurs faisceaux

Abstract : The aim of this thesis is the study of the optically induced laser effect in a polymer thin film doped with a laser dye and excited by multiple laser beams. The laser emission is created by a distributed feedback effect (or DFB) obtained by a temporary longitudinal modulation of the gain induced in the active medium. Using a transient Bragg grating permits to obtain some spectral accordability properties and a lifetime of laser emission around the lifetime of the pump beam.
First, the studied materials are caracterized by a single beam excitation. This study permits to confirm the gap of accordability in the gain spectrum and the tranverse nature of the emitted mode in the waveguide. Experimentally DFB excitation is performed using a Lloyd interferometer which permits a tunability of the device through variation of the interfringe.
Then, these results are used to study the influence of the number of pump beams according to two parameters: the temporal delay between the pumps beams and the order of Bragg reflexion used to obtain the laser emission. This study explains the link between these parameters and the number of emitted laser emission. This number increases for higher reflexion order for coherent superposition of the pumps. The dynamics of the induced gratings was studied by the temporal shifting of the pump beams. Two theorical models are presented. The first is based on a geometrical study of the incident wave vectors on the film and takes into account their inteactions, the second leans on the refractive index saturation of the medium. These models are in good agreement with the experimental results.
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Submitted on : Wednesday, July 4, 2007 - 4:38:08 AM
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  • HAL Id : tel-00159743, version 1

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Adrien Vespérini. Etude du spectre d'émission de lasers à rétroaction répartie dans des couches minces de polymères excités par plusieurs faisceaux. Physique Atomique [physics.atom-ph]. Université d'Angers, 2006. Français. ⟨tel-00159743⟩

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