Surface integrity of precision ground fused silica for high power laser applications

Surface integrity of optics used in high power laser systems is vital to their successful application. Reduction of subsurface damage is demanded during their processing. Rapid grinding of large and complex shape optics can be performed using the BoX® ultra precision grinding machine. Importantly, the depth of subsurface damage induced, even at high material removal rates, has been shown to be very small in comparison to previous studies. In this paper, grinding experiments have been conducted to verify the amount of defects beneath ground fused silica surfaces produced under selected processing conditions. The subsurface damage levels were revealed using a sub-aperture polishing process in combination with an etching technique. Observed subsurface damage can be separated in two distinct depth zones characterised as ‘process’ and ‘machine dynamics’ related.