A two-step physical-chemical etching technique to improve laser damage resistance of fused silica

A two-step physical-chemical etching method, namely large incident angle ion beam etching followed by HF etching, is proposed to remove the damage precursors in fused silica surface to achieve good surface quality and significantly improve the laser damage resistance of fused silica. Ion beam etching with large incident angle is utilized to remove the metal impurities and most subsurface defects in fused silica surface, which can reduce the removal amount of subsequent HF etching of fused silica, thus suppressing the replication and expansion of the subsurface defects, deposition of reaction products and deterioration of surface shape during the HF etching process. After that, HF etching is used to remove the atomic-scale damaged layer and reduce the P–V value of the reflection surface shape induced by ion beam etching. Therefore, a better laser damage performance of fused silica can be obtained by the two-step etching method compared with single ion beam etching and single HF etching. The results show that the two-step physical-chemical etching can be developed to fabricate high-quality and high damage-resistant fused silica optical components with small etching amount and good surface quality for high-power laser application.