Fused silica is widely used in high-power laser systems because of its good optical performance
and mechanical properties. However, laser damage initiation and growth induced by 355 nm laser illumination
in optical elements have become a bottleneck in the development of high energy laser system. In order to
improve the laser-induced damage threshold (LIDT), the fused silica optics were treated by two types of
HF-based etchants: 1.7%wt. HF acid and buffer oxide etchant (BOE: the mixture of 0.4%wt. HF and 12%wt.
NH4F), respectively, for varied etching time. Damage testing shows that both the etchants increase the damage
threshold at a certain depth of material removal, but further removal of material lowers the LIDT markedly.
The etching rates of both etchants keep steady in our processing procedure, ~58 μg/min and ~85 μg/min,
respectively. The micro-surface roughness (RMS and PV) increases as etching time extends. The hardness (H)
and Young’s modulus (E) of the fused silica etched for diverse time, measured by nano-indenter, show no
solid evidence that LIDT can be related to hardness or Young’s modulus.