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Microlasers : Dynamique de Couplage et de Polarisation

Abstract : This work takes place within the general framework of the study of the oscillators coupling. Two aspects are approached which respectively concern the coupling by proximity of two microchip lasers within a same wafer and the interactions between polarisation modes in quasi isotropic microchip YAG lasers.
The experimental study of the two coupled continuous lasers reveals three different dynamic regimes which appear successively as the frequency detuning of the lasers cavities decreases: i) almost independent lasers, ii) periodic and chaotic instabilities and iii) phase locking.
Contrary to most previous studies, the model developed to account for laser coupling introduces a complex coefficient linking the field amplitudes. It remarkably reproduces all the experimental results. This leads us to propose a reliable measurement method of this coupling coefficient. A detailed study of the origins of the coupling, i.e. the overlap between laser modes and the non uniform profile of the gain and of the refraction index, allows to derive an analytical expression of the coupling coefficient which reproduces well the evolution of its real and imaginary parts versus the distance between lasers.
The polarisation dynamics of microchip YAG lasers, and in particular, of the Nd3+,Cr4+:YAG lasers, brings into play the stress-induced birefringence, the gain anisotropy induced by a linearly polarised pump beam and the anisotropy of the saturable absorber. According to the relative importance of these various anisotropies, the laser emits in one and/or the other of the birefringence eigenmodes or can have, in some cases detailed here, a linear polarisation perpendicular to one of the absorber crystal axes.
The experimental observations could be reproduced analytically and/or numerically using a model which accounts for the temporal evolution of the field components along the birefringence eigenaxes as well as that of their relative phase. The basis of this model are discussed.
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Submitted on : Tuesday, July 4, 2006 - 4:36:41 PM
Last modification on : Wednesday, October 21, 2020 - 3:41:26 AM
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  • HAL Id : tel-00083926, version 1

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Géraud Bouwmans. Microlasers : Dynamique de Couplage et de Polarisation. Physique Atomique [physics.atom-ph]. Université des Sciences et Technologie de Lille - Lille I, 2001. Français. ⟨tel-00083926⟩

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