Relationships between subsurface damage depth and surface roughness of grinded glass optics

Relationships between subsurface damage (SSD) depth and peak to valley surface roughness (Rt ) have been widely studied and present a major interest for an easy assessment of the SSD depth. We seek the relation between SSD depth and other surface roughness parameters using the Abbott-Firestone curve on a large campaign of grinding tests (with different abrasive grain size, grinding speed and grinding mode). The results reveal that the Abbott-Firestone parameter Mr2 , which can be linked to the volume fraction of valley in the roughness profile, is more accurate than Rt for an assessment of the SSD depth and that the relationship between Mr2 and the SSD depth varies when changing the grinding mode. Keywords: subsurface damage, surface roughness, Abbott Firestone, fused silica glass 1. INTRODUCTION Many studies tried to define an empi rical relationship between subsurface damages and surface roughness because these damages under surface, mainly due to the manufacturing steps, limit greatly the lifetime of optical components in high energy laser applications such as Laser Megajoule (LMJ) or National Ignition Facility (NIF)