Optical and laser damage properties of 98% deuterium DKDP crystal in different crystal orientations

Served as electro-optic switch, frequency converter and the optical parametric chirped pulse amplifier (OPCPA), highly deuterated DKDP crystals are critical optical elements in high power laser systems. In our work, samples taken in Z direction and type-Ⅰ phase-match direction from an as-grown high deuterium DKDP crystal, which was grown by the rapid growth method with continuous filtration. Thermo-gravimetric apparatus (TGA) measurement was applied to obtain the deuterium content of the DKDP crystal. the results showed the deuterium level of the samples in our experiments exceeded 98%. The ultraviolet-visible-near-infrared transmittance spectrum showed that the transmittance of Z-cut at 532nm and Ⅰ-type at 1064nm were 92.99% and 96.07%, respectively. The 0% laser-induced damage threshold of Z-cut in 1064nm was about 40J/cm2, exceeding much more than the application requirement in certain high power laser systems. The polarization state of laser had little effect on the laser-induced damage characteristics of Ⅰ-type sample. Then the laser-induced damage morphologies of 98% DKDP crystals induced by the 1064nm and 532nm lasers were investigated. The results indicated that the "micro-explosion" of different kinds of defects in the bulk led to different damage morphologies, and many cracks in the damage pinpoints presented the regular orientation with better consistency in view of the type-Ⅰ phase-match direction. Our research can provide a reference for the applications of highly deuterated DKDP crystals in high power laser systems.