Ultraviolet Laser-Induced Damage Characteristics of 70% Deuterated Potassium Dihydrogen Phosphate Crystals

Bulk damage of deuterated potassium dihydrogen phosphate (DKDP, KD2PO4) crystal can be induced by intense laser irradiation, severely restricting the output of high- power laser energy and the usage of DKDP crystals in high-power laser systems. In this paper, laser-induced damage threshold (LIDT) and damage growth characteristics of DKDP crystal under 355 nm laser irradiation were systematically studied. The bulk laser-induced damage (LID) density of the crystal increased exponentially with the increase of the laser irradiation fluence. LID closely relates to the growth defects called precursors. Laser conditioning could effectively enhance the LID resistance by modifying the precursors. The LID density of DKDP crystals decreases after laser conditioning, and the increasing conditioning fluence can reduce the LID density. Damage growth after the initial LID by 1-on-1 measurement is different from that by R-on-1 measurement since the process of R-on-1 measurement leading to initial LID is equal to the laser conditioning procedure. The study in this paper provides a reference for improving the application of DKDP crystal in high-power laser systems.