具有π共轭平面结构单元的新型红外非线性光学材料的设计、合成、晶体生长和性能研究

It is very challenging to get the correct understanding of the composition-structure-property relationship for IR nonlinear optical (NLO) materials. Planar structural units with π conjugated electrons have been proved to be one of the best NLO-active structural units in the UV and visible range. However, the study on IR NLO materials with such units is very limited. In our previous study on BaHgSe2, we identified, for the first time, the trigonal planar [HgSe3] unit as a new kind of basic functional groups to confer large NLO susceptibilities and physicochemical stability in IR NLO materials. Based on these encourging results, we propose in this project to carry out a systematic investigation of IR NLO materials containing planar structural units. Our research will include (1) design andl synthesis of IR NLO materials with planar structural units such as HgQ3（Q=S,Se,Te）and GaP3 groups. We wil optimize the arrangement of the functional groups by the controlling effect of cations; (2)crystal growth of suitable materials and the detailed measurements of the NLO and other properties of the crystals; (3) systematic investigation of the influencing rules of the composition, connectivity, packing density of the planar structural units on the various properties of the IR NLO materials to provide guidance for searching new crystals structurally different from the traditional chalcopyrite materials . This project will open a new direction for the study of IR NLO materials. It will also have important inspiration for the molecular design and exploration of function-oriented crystalline materials and help to improve China's international status in the study of IR NLO crystals.

准确认识红外非线性光学材料的组分-结构-性能之间关系是极具挑战性的工作。具有π共轭体系的平面结构单元在紫外和可见光区已被证实是一类最佳非线性光学效应基团，但含此类基团的红外非线性光学材料研究十分匮乏。申请人在BaHgSe2中首次发现效应大且结构稳定的红外平面效应基团HgSe3。本项目拟在前期工作基础上，深入研究含有平面效应基团的红外非线性光学材料，包括：①继续设计合成含HgQ3（Q=S,Se,Te）和GaP3等平面基团的红外材料，利用阳离子调控作用实现基团优化排列；②选择材料生长块状晶体，详细测定晶体的非线性光学等性质；③总结平面效应基团组成元素、连接方式、堆积密度等因素对材料性质的影响规律，为寻找结构不同于传统黄铜矿类材料的新型晶体提供指导。本项目将开辟红外非线性光学材料研究的一个新方向，对功能导向晶态材料的分子设计和探索有重要启示，有利于提高我国在红外非线性光学晶体研究方面的国际地位。

具有π共轭体系的平面结构单元在紫外和可见光区已被证实是一类最佳非线性光学效应基团，由于它们具有较大的微观二阶敏感性和各向异性，在构建良好的紫外和深紫外非线性光学材料方面，已经取得了巨大的成就。但是具有π共轭体系的平面结构单元在红外非线性光学材料中的研究十分匮乏。2016年我们在BaHgSe2中首次发现效应大、结构稳定的红外平面效应基团HgSe3。根据周期表中对角线元素性质相似性原则，我们在Ag6HgSiSe6 材料中进一步发现AgSe3平面基团也和HgSe3类似，对其强非线性效应（d32 = 43pm/V）做出主要贡献。并发现了KHg4Ga5Se12，K2ZnSn3Se8，Hg2GeSe4和Zn3P2S8等多种性能优良的新型红外非线性光学材料。此外BaHgSe2晶体的生长研究获得进展，单次合成多晶原料30g以上，生长出厘米级的BaHgSe2单晶。