Effects of chemical etching on the surface quality and the laser induced damage threshold of fused silica optics

Effects of deep wet etching on the surface quality and the laser induced damage probability have been studied on fused silica samples. Results obtained with a HF/HNO 3 solution and a KOH solution were compared on both polished pristine surface and scratched surfaces. The hydrofluoric solution radically deteriorated the surface quality creating a haze on the whole surface and increasing considerably the roughness. For both solutions, neither improvement nor deterioration of the laser damage performances has been observed on the etched surfaces while the laser damage resistance of scratches has been increased to the level of the surface. We conclude that laser damage performances are equivalent with both solutions but an acid etching induces surface degradation that is not experienced with basic etching.