三倍频激光辐照下DKDP晶体体内本征点缺陷的演化机制研究

Nanosecond third-harmonic laser induced damage of deuterated potassium dihydrogen phosphate (DKDP) crystal is an important scientific issue in damage-resistance research of high-power laser system. The evolution of intrinsic point defects in DKDP under intense laser irradiation has substantial connection with damage precursor properties and the damage resistance of DKDP crystal. For this reason, we propose this project to investigate the evolution of intrinsic point defects in DKDP crystal under third-harmonic laser irradiation. In the project, we are going to build a theoretical electronic transition model in DKDP with nanosecond third-harmonic laser excitation to discuss the mechanism of defect-assisted laser absorption and energy deposition. We will construct an evolution model of intrinsic point defects under third-harmonic laser irradiation, analyze the laser-induced intrinsic point defect generation and recombination progress, and then elucidate the generation/recombination reaction mechanisms at the micro level. The rules of how intrinsic point defect evolution affect the damage precursor properties in DKDP crystal will be revealed. The research results of our proposed project will provide essential scientific evidence to better understand mechanisms of laser-induced damage and laser conditioning of DKDP crystal.

氘化磷酸二氢钾（DKDP）的三倍频激光诱导损伤是高功率激光装置负载能力提升研究中的重要科学问题。强激光加载下DKDP晶体体内本征点缺陷的演变行为与晶体的损伤前驱体特性、晶体的抗激光损伤性能密切相关。本项目拟开展三倍频激光辐照下DKDP晶体本征点缺陷演化机制研究，建立DKDP晶体在三倍频纳秒激光激发下的电子跃迁理论模型，探讨缺陷辅助的激光吸收和能量沉积机制；构建三倍频激光作用下DKDP晶体本征点缺陷演化模型，分析激光诱导DKDP晶体本征点缺陷产生及激光作用下本征点缺陷复合的动力学过程，阐明DKDP晶体体内本征点缺陷产生和复合反应的微观机理；揭示晶体体内本征点缺陷的演化对晶体损伤前驱体特性参数的影响规律。本项目的研究成果将对理解DKDP晶体激光诱导损伤和激光预处理的内在机制提供重要基础和科学依据。

DKDP晶体是制备大口径激光装置终端三倍频频率转换元件的重要材料，其激光诱导损伤问题是制约激光装置输出性能进一步提升的关键因素之一。DKDP晶体体内的本征点缺陷与晶体元件在强激光加载下的抗激光损伤性能密切相关。本项目针对三倍频激光辐照下DKDP晶体体内本征点缺陷的演化问题开展研究，基于缺陷辅助的能量吸收模型计算了晶体在三倍频激光辐照下的吸收跃迁过程，研究了材料初始缺陷水平、激光参数对能量沉积的影响；利用瞬态吸收光谱研究了紫外激光作用下DKDP本征点缺陷产生和复合的动力学过程，明确了产生点缺陷的类型和缺陷演化的时间特性；利用光谱表征、正电子湮灭寿命谱表征等方法研究了三倍频亚纳秒激光作用下DKDP晶体体内本征点缺陷演化特性，并开展了不同激光参数预处理后DKDP晶体的损伤性能提升规律研究。本项目的研究为理解DKDP晶体的激光诱导损伤机理及激光预处理性能提升的物理机制提供了参考和依据。