Subsurface damage of fused silica lapped by fixed-abrasive diamond pellets

Minimizing subsurface damage (SSD) is in high demand for optics during grinding, lapping, and polishing. A fixed-abrasive diamond pellet (FADP) has been validated as a potential tool in fast lapping and polishing of hard optical materials. This study inspects and measures the SSD of fused silica developed in lapping and microlapping by FADPs tool through a taper polishing method, assisted with profile measurement and microexamination. A series of experiments is conducted to reveal the influence of lapping parameters on SSD depth and surface roughness, including diamond size, lapping pressure, and velocity, as well as rubber type. Results indicate that SSD depth and surface roughness are mostly sensitive to diamond size but are generally independent of lapping pressure and velocity. Softer rubber can reduce SSD depth and improve surface roughness. The ratio of SSD depth to surface roughness (peak to valley: Rt) is confirmed to be 7.4±1.3, which can predict the SSD depth of fused silica lapped by FADPs with a rapid roughness measurement.