不同晶向98%高氘晶体的光学及损伤性能研究

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.

高氘代DKDP晶体可作为电光开关、变频器以及光参量啁啾脉冲放大器（OPCPA），是高功率激光系统中的关键光学元件。本研究采用连续过滤快速生长法制备原生高氘代DKDP晶体，并从中切取沿Z方向与Ⅰ型相位匹配方向的样品。通过热重分析仪（TGA）测试表征了该DKDP晶体的氘含量，结果显示本实验样品的氘代率超过98%。紫外-可见-近红外透过光谱测试结果表明，Z切样品在532nm波长处的透过率为92.99%，Ⅰ型切样品在1064nm波长处的透过率为96.07%。Z切样品在1064nm波长下的零概率激光诱导损伤阈值约为40J/cm²，远高于部分高功率激光系统的应用要求。激光偏振状态对Ⅰ型样品的激光诱导损伤特性影响微弱。随后我们研究了氘代率达98%的DKDP晶体在1064nm与532nm激光辐照下的激光诱导损伤形貌。结果表明，晶体内部不同类型缺陷的"微爆炸"效应会引发各异的损伤形貌；且从Ⅰ型相位匹配方向观测时，损伤点周边的大量裂纹呈现出规则取向且一致性较好。本研究可为高氘代DKDP晶体在高功率激光系统中的应用提供参考依据。