Influence of Light Intensification by Subsurface Cracks on KH2PO4 Crystal's Laser Induced Damage Threshold

Abstract

The subsurface damage introduced by single point diamond turning (SPDT) is an important precursor that decrease the laser induced damage threshold (LIDT) of KH2PO4 (KDP) crystal. In this paper, based on the Fourier model theory, the modulation property of subsurface crack is analyzed. Research results indicate that light intensification by subsurface crack is an important mechanism of KDP failure. When the feed speed increases under the certain cutting depth, the subsurface damage depth and LIDT have the inverse changing trend. Namely that the intention of obtaining smaller damage depth by choosing suitable cutting parameters, will be also beneficial to improve the surface LIDT of KDP crystal. The combination of feed and cutting depth decides the damage depth together under the given spindle speed and tool geometry. The small feed is beneficial for improving the LIDT when cutting depth is large, while the situation is opposite when cutting depth is small.