Effect of pad elastic modulus on polishing-induced subsurface damages distribution and laser-induced damage performance of fused silica optics.

Abstract

The plastic subsurface damages distribution and their influence on the laser induced damage performance of fused silica optics polished with different pads are investigated. The elastic interaction model, plastic indentation model and wear relationships are combined together to theoretically characterize the plastic subsurface damages distribution in different polishing processes, which shows consistent results with experiments. It reveals that most of the polishing-induced subsurface damages are plastic damages. A few largest polishing particles in the tail end distribution mainly decide the final depth distribution and density of the polishing-induced plastic subsurface damages. The larger pad elastic modulus will make the few largest polishing particles bear much larger load and generate larger proportion of observable plastic subsurface damages. Using polishing pad with lower elastic modulus is prominent for restricting the generation of fractures and plastic damages and finally makes the polished optics show higher laser induced damage threshold, lower damage density and smaller slope damage probability curve. This research is meaningful for further establishing the quantitative relationships between polishing parameters, subsurface damages distribution and laser induced damage performance in fused silica optics.