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AbstractAbstract
[en] The chirped pulse amplification demonstrated in 1985 allowed the development of petawatt class laser such as Petal (Petawatt Aquitaine Laser). The increase of power of those facilities is limited by the resistance to laser-induced damage of the optical components placed after the compression stage. The aim of this thesis is to improve the laser-induced damage threshold of those components which are multilayer dielectric mirrors. Three paths of improvement are considered the change of design (number of layer, thicknesses), of materials and/or deposition process. A numerical study allows evaluating the potential improvement brought by two of those paths. This led to the development of a design optimization algorithm that required the prior characterization materials. Consequently, various materials deposited as single layers were laser damage tested and optically characterized to evaluate the adequacy of the materials with the deposition process. The results show a wide discrepancy that cannot be explained by the laws exposed in the literature. However, a good correlation was found between the intrinsic laser-induced damage thresholds in the infrared with the absorption in the ultraviolet confirming the influence of the multiphoton absorption in the laser-induced damage mechanisms. Finally, those experimental results combined with the optimization algorithm allowed the development of mirror samples that exhibit laser-induced damage threshold 73% higher than one of classical mirrors. (author)
[fr]
L'amplification par derive de frequence demontree en 1985 a permis la creation d'installations laser en impulsions courtes tels que Petal (Petawatt Aquitaine Laser). La montee en puissance de ces lasers est limitee par la resistance au flux laser des composants places apres la compression. L'objectif de cette these est d'ameliorer la resistance au flux laser de ces composants qui sont des miroirs qui consiste en un empilement multicouches. Trois approches sont envisagees: le changement de designs des empilements couches minces (nombre de couche, epaisseurs), de materiaux et/ou de procedes de fabrication. Une etude numerique a permis d'envisager theoriquement le changement de materiaux et/ou de design et de quantifier les ameliorations possibles. Cette etude a mene au developpement d'un algorithme d'optimisation des designs qui necessite la caracterisation prealable des materiaux. Par consequent, une variete de materiaux deposes en monocouches a ete testee au flux laser et caracterise optiquement pour evaluer l'adequation materiaux et technique de depot. Les resultats obtenus montrent une forte dispersion qui ne peut etre explique par des lois prealablement etabli dans la litterature. Cependant, une bonne correlation entre le seuil de tenue au flux laser intrinseque dans l'infrarouge et l'absorption dans l'ultraviolet a ete observe ce qui confirme l'influence de l'absorption multi-photonique sur l'endommagement laser en impulsions courtes. Pour finir, l'ensemble de ces resultats experimentaux et de l'algorithme d'optimisation ont permis la fabrication d'echantillons de miroirs qui montrent une amelioration du seuil de tenue au flux laser de 73% par rapport a des miroirs quart d'onde classiquesOriginal Title
Etude des traitements multicouches utilises dans un environnement a faible hygrometrie sur les installations laser de puissance
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23 Oct 2019; 177 p; 165 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; Laser, Matiere et Nanosciences
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Report
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Thesis/Dissertation
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