Building high-damage-threshold surfaces at 351 nm

In the field of the development of LIL and LMJ fusion class high power lasers, CEA has made important efforts to understand and improve laser induced damage threshold of fused silica optics at the wavelength of 351 nm. Since several years, we have focused on optimizing the grinding, polishing and post polishing processes to overcome the existing performances with various industrials and academics partners. In this paper, we describe our understanding of the nature of the polished silica interface and our approach to rich our damage threshold goal. Our efforts were mainly put on reducing the cracks region extension and removing or optimizing the polishing top layer. We give also some details on the influences of each of the polishing process from rough material grinding to post processing. We demonstrate that some order of magnitude in laser damage initiation density can be gained by combining appropriate fabrication steps.