具有高激光损伤阈值的卤化物中红外非线性光学晶体材料的设计合成与性能研究

The nonlinear optical (NLO) crystals to be used in the mid-infrared (mid-IR) region are very important in the fields of laser spectroscopy, optical communication and high intensity laser confront etc. However, the laser damage threshold (LDT) of the currently commercialized mid-IR NLO crystals is too low, so they are difficult to meet the requirements for high intensity laser application. Therefore, to explore novel mid-IR NLO crystal materials with large LDT, strong NLO effect and appropriate mid-IR transmission range has very important academic significance and practical application prospect. In this project, we shall exclude the structural modification from the existing chalcopyrite semiconductor materials, and mainly focus on the structure from insulating compounds such as halides including halide salts and halogenated oxygen-containing salts with wide energy gap so as to show large LDT. The goal of this project is to increase greatly the laser damage threshold of mid-IR NLO crystal material, also to take into account strong NLO effect and wide IR transmission as well as high environmental stability and good crystal growth habit. In the implementation of the project we shall make full use of computer simulation for molecular design and selection of reasonable structure, and then complete the synthesis, structural characterization, performance studies of new materials, and also carry out the crystal growth to a large size. We expect to obtain a number of new mid-IR NLO crystal materials with excellent comprehensive performances, and lay a solid foundation for its practical applications.

中红外波段非线性光学晶体材料在激光光谱、光通讯和战场激光武器对抗等方面有十分重要的应用。目前商用中红外波段非线性光学晶体均存在激光损伤阈值低的缺点，很难满足高强度激光应用的要求，因此开展具有高激光损伤阈值并兼具较大非线性光学效应和较宽红外透过范围的新型中红外波段非线性光学晶体材料的探索具有重要的学术意义和实际应用前景。本项目撇开已有黄铜矿半导体材料的红外非线性晶体结构选型，拟从具有高能隙的绝缘化合物主要是卤代酸盐和卤代含氧酸盐中探索新型中红外非线性光学材料，目标是大幅提高晶体材料激光损伤阈值，兼顾大的非线性光学效应和宽的红外透过范围，同时具有高稳定性和良好晶体生长习性等综合性能。项目实施中充分利用计算机模拟进行合理分子设计和结构选型，进而完成这类新型材料的合成制备、结构鉴定，研究各种性能，开展大尺寸晶体生长，探索出若干个综合性能优良的新型中红外非线性光学晶体材料，为其实际应用打下坚实基础。

目前商用黄铜矿型红外波段非线性光学晶体多属于半导体材料，带隙较窄，激光损伤阈值普遍较低，很难承受高强激光作用，使其应用范围受到很大局限，因此探索具有高激光损伤阈值同时兼具较大非线性光学效应的新型红外波段非线性光学晶体材料成为当前非线性光学材料领域的前沿挑战课题之一，具有重要的学术研究意义和实际应用前景。由于材料的激光损伤阈值与其带隙密切相关，本项目在国家自然科学基金重大研究计划资助下，撇开已有黄铜矿半导体材料的红外非线性光学分子结构选型，着重从含有卤素原子的宽带隙化合物着手，通过合理的分子设计与结构选型，合成了一系列的卤代含氧酸盐和氧酸盐中红外非线性光学材料，比较系统地研究了它们的各种光学性能和热稳定性能，并结合理论计算研究了它们的非线性光学效应的起源，深入探讨了结构与性能之间的关系，得到了多个具有高激光损伤阈值同时具有较强非线性光学效应且综合性能优良的中红外波段非线性光学晶体材料；同时，通过理论计算并结合实验结果较系统地研究了卤化物（包括卤代酸盐）非线性光学晶体材料中分子结构的变化对其非线性光学性能的影响，总结了这类非线性光学材料的结构与性能之间的关系，对新型结构卤化物中红外非线性光学晶体材料的探索提供了有益的指导，并从卤化物中获得了一些具有高激光损伤阈值的非线性光学晶体材料，丰富了卤化物中红外非线性光学晶体材料的研究内容。此外，初步开展了部分综合性能优良的红外波段非线性光学晶体材料的单晶生长探索，为后续相关材料的大尺寸晶体生长及其综合性能评估积累了一定的实验研究经验。