Destructive methods for detecting subsurface defects of fused silica optics

Subsurface damage will be generated in grinding, lapping and polishing process, the subsurface defects such as micro cracks, scratches and residual stress will decrease the anti-laser-induced damage ability of fused silica optics. How to quickly and accurately detect subsurface damage becomes a vital problem in the field of optics manufacturing. In this paper, subsurface damage morphology and depths of fused silica optics were detected and analyzed by HF acid etching, taper polishing and MRF slope polishing methods. The results show that there are some differences in the test results of subsurface damage depth by different detection methods, the subsurface damage depths obtained by HF acid etching method are larger than those obtained by taper polishing and MRF slope polishing methods. The larger the abrasive particles are, the more serious the phenomenon of brittle fracture in surface and subsurface will be, and the greater the depth of subsurface defects will be.