Effect on nanoscale damage precursors of fused silica with wet etching in KOH solutions

Abstract

We investigate the nanoscale damage precursors that will cause laser damage initiation on fused silica surface during KOH-based wet etching. Some nanoscale damage precursors, like impurity contamination and chemical structure defects on different etched surface with a KOH solution, are explored through a variety of testing methods at nanoscale spatial resolution. The etched surface roughness and photothermal absorption level are also studied. The results show that KOH-based etching can keep a good surface roughness, reduce impurity contamination significantly, and thus decrease surface photothermal absorption level. However, it can mitigate little chemical structure defect and has a risk of secondary pollution induced by residual deposition such as K2SiO3. The work can be a reference on using KOH-based wet etching technology to mitigate nanoscale damage precursors of fused silica ultraviolet optics.