Subsurface defects characterization and laser damage performance of fused silica optics during HF-etched process

Subsurface defects of fused silica optics would vary with HF-etched process. In this paper, the subsurface defects characteristics of HF-etched fused silica optics and their effects on laser induced damage were investigated. The results suggest that most of metal impurities defects (especially Ce element) of fused silica optics can be dissolved in strong acid solution. Subsurface damage can be removed by submerging fused silica optics in HF-based etchants. Laser damage resistance is improved through the removal of metal impurities and subsurface damage. Optical thermal absorption describes the laser absorption characterization of fused silica subsurface layer. A good correlation between optical thermal absorption and laser-induced damage performance is shown in this paper. Laser damage performance deteriorates when the HF-based etching depth exceeds one value, which can be explained by the impurities redeposition and surface roughness increase. Research results have a guiding significance for HF-based etching process technology of fused silica optics.