Improvement of laser damage thresholds of fused silica by ultrasonic-assisted hydrofluoric acid etching

Li Yuan^{1, 2}, Yan Hongwei², Yang Ke², Yao Caizhen², Wang Zhiqiang², Yan Chunyan¹, Zou Xinshu², Yuan Xiaodong², Yang Liming³, Ju Xin^{1, †}

(a) Confocal fluorescence microscope images and (b) PL defect concentrations of the samples. A refers to the sample without etching. B–D are samples etched by the following conditions: 5 wt.% HF, 3 μm removed; 40 wt.% HF, 3 μm removed; and 5 wt.% HF, 6 μm removed. The unit of ppm refers to part per million.