Bulk And Surface Damage Thresholds Of Crystals And Glasses At 248 nm

Abstract

We used 20 ns, 248 nm pulses to study surface and bulk damage in bare, polished samples of UV-transmitting glasses, fluoride crystals, and isomorphs of potassium dihydrogen phosphate (KDP). The intent was to test enough samples to establish the safe operating limits for currently available windows and crystals finished by routine techniques for optical fabrication. In fluoride crystals, thresholds for bulk inclusion damage and for rear-surface damage were comparable. The median rear-surface threshold was 16 J/cm2. The fluence limit in fused silica windows was determined by the threshold for rear-surface damage, which ranged from 5 to 9 J/cm2. For the isomorphs of KDP, the limiting fluence was the threshold for front-surface damage, which ranged from 3 to 9 J/cm2.