Combination of scanning ion beam etching and dynamic chemical etching for improving laser damage resistance of fused silica optics

Abstract

A new method that combines scanning ion beam etching (IBE) and dynamic chemical etching (DCE) is proposed to tracelessly remove the subsurface damage (SSD) layer of fused silica optics to improve their laser-induced damage resistant performance. Several characterization techniques are employed to investigate the influence of the etching depth of each individual step on the optical properties of the treated sample surfaces, which helps to provide a guide for its implementation in practice as well as improve our understanding on the mechanism of the proposed combined method. The results indicate that traceless removing of SSD layer is accomplished with a shallow 0.3 μm-IBE treatment. Nevertheless, secondary defects such as metal contaminations are introduced at the same time, which induces optical absorption even higher than that of the conventionally polished sample. These secondary defects can be effectively removed with a 3 μm-DCE treatment, achieving high-quality surface with laser-induced damage threshold much higher than that of the 10 μm-DCE etched sample and surface roughness as low as that of the virgin sample. The combined treatment of scanning IBE and DCE shows an excellent performance in improving the damage resistance of fused silica optics without deteriorating their surface quality.