Effect of ion beam etching on surface/subsurface structural defect evolution in fused silica optics

Ion beam etching through physical sputtering can also improve the laser-induced damage threshold of fused silica optics without introducing precipitation products or toxic fluoride solution, which makes ion beam etching an attractive alternative method for post-treatment. Researches indicated that ion beam etching could partially remove surface scratches and reduce the surface roughness of fused silica optics. In this study, the effects of ion beam etching on surface/subsurface structural defect evolution of fused silica optics were investigated. The results showed that chemically inert ion beam etching completely removes plastic subsurface structural defects and partially removes surface structural defects. Because of the lack of a sacrificial layer, ion beam etching has much lower removal efficiency for surface structural defects, especially deep structural defects, than for subsurface structural defects.