The Influence of Etching Depth on Surface Molecular Structures and Laser Damage Thresholds of Fused Silica by using Megasonic-assisted HF-based Etching

摘要

The laser induced damage of fused silica optics significantly restricts the output ability of high power laser systems. Hydrofluoric (HF)-based etching is an effective method to increase the laser induced damage thresholds (LIDTs) of fused silica by eliminating impurities and mitigating subsurface defects. In this research, traditional polished fused silica samples were etched for different time in a HF-based etchant (2.3 wt.% HF and 11.4 wt.% NH4F) assisted by a 1.3 MHz megasonic field. The LIDTs were measured by R-on-1 mode. Fourier transform infrared absorption spectra of etched samples were also characterizaed. Results showed that the LIDTs of the fused silica samples increased with the increasing of etching depth, which may due to the elimination of the densified materials induced by the manufacturing process.