Modélisation de la diffraction des faisceaux lasers d'ordres supérieurs

Abstract

Since the invention of lasers, this magical device that generates a very special and very interesting light has invaded research laboratories and industrial boxes. And since the laser light is coherent, the phenomenon of diffraction appears during each passage of a laser beam by an obstacle. The theoretical and experimental work presented in this thesis is focused on shaping by diffraction modeling by amplitude objects laser beams of the Hermite-Gaussian type. The problems concerning the calculation of diffraction integrals have been dealt with differently, Analytical expressions have been developed to accurately describe the diffraction behavior of Hermite Gauss HGm0 beams by diaphragms and stops on the whole focal region, including the focal plane. Through the simulations made on the analytical results found, it has been confirmed the validity of the various mathematical developments that have been proposed. The beam shaping performed showed that we can get beams have interesting forms. Foremost, we give an overview of the literature on HG laser beam theory, followed by the generation of these using the SLM. The generated beams will serve as a basis for studying the effect of truncation by a diaphragm on them. The results obtained have shown that it is possible to generate lower order HG beams from those of higher orders , using a robust method based on truncation by a diaphragm. The interest in terms of costs is then significant. The interpretation of this result, was completed by a very precise analysis of quality factor M2. We also showed that, a simple high pass filter (stop) is capable of self healing the initial beam based on Abbé experience