Effects of acid-etching depth on 355 nm laser-induced damage threshold of fused silica

The effects of chemical etching with a buffered HF solution on fused silica surface were studied by measuring the etched depth, via interferometer and step meter, and etched material mass under different etching time. The depth etching rate and material removal rate became constant after about 8 min etching. The redeposition layer of optical polished surface was about 16 nm, while the subsurface defect layer was deeper than 106 nm. The laser-induced damage threshold and surface roughness before and after chemical etching were also measured. The results showed that, firstly, the damage threshold increased with the removal of the redeposition layer. Then, it decreased with the exposure of the subsurface defects followed by an increase with the increase of etching time. Finally, it was almost