Laser-induced damage resistance improvement of fused silica optics by wet etching process

In this thesis, laser-induced damage resistance improvement of fused silica optics is investigated in the nanosecond regime. This material is used on high power laser facilities such as the Laser Megajoule. In order to improve the optics life time and to ensure the nominal operation of this facility, laser induced damage has to be controlled. This phenomenon is an irreversible modification of the components surface because of the interaction between the laser beam and precursors defects. These defects are a consequence of the synthesis of silica and the polishing of the optics and their presence can be reduced by a wet etching. This process consists in an erosion of the surface using a chemical solution however optical properties must remain unchanged. In this thesis, we focus on the wet etching process and we conduct three studies. The first one is about the characterization of the polishing induced contamination and the capability of a wet etching to remove it from the surface. The second and the third analyzes are about the impact of the wet etching respectively on the surface and on the scratches. These studies allow us to evaluate the influence of the wet etching parameters as the chemical solution, the system used and the deep etched. Finally, the highlights obtained thanks to these studies enable to optimize the wet etching process and improve the laser induced damage resistance of components without compromising their optical properties. (author)