Etching behavior of ground fused silica and light enhancement modulated by surface/subsurface cracks

Abstract

Abstract The mechanical defects (scratches/cracks) originated from grinding processing need to be dislodged so that improving the optical performance of fused silica. In this paper, HF‐based (HF represents hydrofluoride acid) etchant was used as a subsequent fabrication for loose‐abrasive ground fused silica, and the surface morphology and characteristics of samples were evaluated, meanwhile, the electric/light field distribution around treated cracks was simulated using the finite difference time domain (FDTD) method. The results show that sufficient material removal amount blunts the cracks to be a series of parabolic‐shaped and smooth craters fused with each other, whose diameter and depth grow as a power function with etched depth. Triple subsurface defect depth should be removed so as to mitigate surface roughness to be ∼2.46 µm and promote transmission from initial 22.55%–54.02%. FDTD simulation results reveal that deep etching alleviates the light intensification factor (LIF) of craters within 1.8 as the diameter‐to‐depth ratio of craters is increased over 10. Moreover, a thickness removal model of ground fused silica involving the cracks distribution characteristics, cracks etching behavior as well as the LIF variation of craters is established, in which the supposed etched depth is determined to promote the manufacturing efficiency and laser damage resistance of the material.