强激光辐照下DKDP晶体中H/D类结构缺陷诱导晶体损伤的机制和规律研究

DKDP crystal is one of the most optimum candidates for the frequency conversion in large-aperture high-power laser system.As high-power laser propagates through the crystal, laser-induced damage will be serious, which limits the output capability of the laser system. Studies show that the defect-assisted nonlinear absorption is one of the most important mechanisms for the damage. It is significant to clarify the influence of every defect on the damage. In our previous research on the crystal growth and crystal damage, we found that H/D structral defect dominates the reasons for the damage of DKDP crystals at present. Thus, we propose to research on the mechanism and regularity of the H/D structral defect in DKDP crystal inducing crystal damage under strong laser irradiation. This project will firstly investigate the distribution of the H/D structral defect and its influcence factors. Then the assisted mechanism of the H/D structral defect on the nonlinear absorption will be explored further. Finally,we intend to establish the connection of H/D defect-assisted nonlinear absorption and the damage properties. The research results will provide theoretical basis and references for improving the quality of DKDP crystal and the optimizing of its application strategy.In addition, the research will constitute a basis for solving the bottleneck problem of crystal damage in intense laser drivers.

DKDP晶体是大口径强激光系统中最佳的紫外倍频材料之一，强激光下DKDP晶体出现严重的体损伤，成为制约强激光系统能量提升的瓶颈。缺陷辅助的非线性吸收是引起晶体损伤的重要机制，明确各种缺陷对晶体损伤的影响一直以来是晶体损伤研究的重点。通过多年来对DKDP晶体生长及损伤过程的深入研究，我们发现H/D类结构缺陷是现阶段制约晶体损伤性能提升的关键。据此，本项目将研究强激光辐照下DKDP晶体中H/D类结构缺陷诱导晶体损伤的机制和规律。拟首先研究H/D类结构缺陷的分布规律及影响因素，探索H/D类结构缺陷对晶体非线性吸收的辅助机制，建立H/D类结构缺陷辅助非线性吸收和晶体损伤的关联性。该项目研究成果将为DKDP晶体生长工艺及晶体使用策略优化提供科学依据，为解决工程装置中DKDP晶体损伤这一瓶颈问题奠定基础。

H/D类结构缺陷辅助的非线性吸收是引起DKDP晶体损伤的重要机制。本项目基于生长动力学分析论证了H/D类结构缺陷形成机制，其形成包含生条件波动、杂质金属离子吸附、H/D键与PO4耦合作用及生长位错畸变等四类机制。在此基础上研究了KDP/DKDP晶体的非线性吸收性能，采用多光子吸收模型对非线性吸收特性进行了分析，研究指出激光激发过程可能引发了新缺陷产生。最后，从微观和宏观层面研究了非线性吸收和损伤的关联性，发现了非线性吸收系数和H/D类缺陷寿命的关联性，证实了非线性吸收是引发晶体损伤的前级过程。通过以上研究使得H/D类结构缺陷、非线性吸收和损伤的关联模型更为清晰明确，该项目研究成果将为DKDP晶体生长工艺及晶体使用策略优化提供了依据,为解决强激光装置面临DKDP晶体严重损伤的瓶颈问题奠定了基础。