基于氧-卤阴离子结构调控的中红外非线性光学晶体结构设计及性能研究

非线性光学晶体是固体激光器获得中红外激光的核心基础材料，在军事和民用的许多领域拥有重要应用。目前商业化的硫、磷属晶体带隙小、激光损伤阈值低、不利于高功率激光产生。本项目拟以带隙大、激光损伤阈值高的金属氧化物和卤化物为研究对象，以“结构基元+取向控制”的结构设计模式将两者进行有序结合。一方面利用氧、卤阴离子配体的电负性差异，通过调节它们在配位多面体中的比例，增加结构基元的微观极化强度；另一方面根据氧、卤阴离子配位时亲核性的不同，调控微观结构基元的空间取向，设计合成出系列具有大倍频、高激光损伤阈值的中红外非线性光学新晶体；并通过其构效关系研究，揭示结构中氧、卤阴离子比例及基元取向对材料倍频效应、激光损伤阈值和红外透光特性等的影响规律和机理；并对综合性能优异的晶体开展厘米级单晶生长研究，加工晶体器件，评估应用前景。项目将能为中红外非线性光学晶体的高效设计提供新思路，丰富非线性光学晶体的材料体系。

Nonlinear optical (NLO) crystal is the key material for solid-state laser to obtain mid-IR laser, which has important applications in military and civil fields. At present, the commercialized chalcogenide and phosphide NLO crystals have small band gaps and low laser damage thresholds (LDTs), which are not conducive to their application for producing high-power mid-IR laser. In this project, metal oxides and halides with large band gaps and high LDTs will be studied. They will be combined orderly in the structural design mode of designing fundamental building units (FBUs) and controlling orientations. On the one hand, we will use the electronegativity difference of oxygen and halogen anion ligands to increase the micro polarization intensity of FBUs by adjusting their proportion in the coordinated polyhedra. On the other hand, we will also adjust the orientation of micro FBUs by using the different nucleophilicity of oxygen and halogen anions. By doing these, we will design and synthesize a series of mid-IR oxygen-halide NLO crystals with large second harmonic generation (SHG) and high LDTs. Through the study of structure-activity relationship, the influence mechanism of the proportion of O2- and F- anions and the orientation in the FBUs on SHG, LDTs and infrared transmission will be revealed. We will also grow the the crystal with excellent comprehensive performance and evaluate their application as mid-IR NLO crystals. The project will provide new ideas for the efficient design of mid-IR NLO crystals and enrich the material system of NLO crystals.