基于DAST的有机太赫兹晶体结构设计、生长机理和构效关系研究

有机非线性光学晶体具有非线性系数大，结构设计简单和易剪裁等优点，在THz波产生和探测方面有重要应用价值。而具有“离域大π键”结构的DAST晶体是目前产生THz波效率最高的晶体，但该晶体存在热稳定性差，空气中使用寿命短和可控生长困难等问题，制约其在THz领域的应用。本项目拟从DAST的阴阳离子二元“离域大π键”结构出发，设计具有共轭骨架、强电荷转移能力的新型非中心对称有机晶体结构。通过创新功能基元空间排列设计，提高晶体结构的非中心对称性和晶体生长稳定性。结合晶体生长机理研究，创新有机晶体生长装置设计，实现大尺寸高质量晶体的可控生长。分别利用差频和光整流法测试晶体THz性能，优化相位匹配方式，解决THz波辐射转换效率低的问题。结合晶体结构设计，建立关键功能基元及其空间取向排列对晶体结构、生长稳定性和THz性能的作用机理，发展有应用价值的新型有机THz晶体，形成自主知识产权。

The organic nonlinear optical crystals have important application values in terahertz (THz) wave generation and detection owing to their large nonlinear optical coefficient, simple design and tailoring in structure, etc. Especially the DAST crystal with“delocalization large π”structure, is regarded as one of the most efficient organic crystals in THz waves generation so far. But the applications in the fields of THz of DAST crystal are restricted due to its poor thermal stability, shorter lifespan in air, and difficulties in controlling crystal growth and so on. From these prblems, we aim to design new types of non-centrosymmetric organic crystal structures with conjugate skeletons and strong charge transfer abilities based on the anion-cation binary “delocalization large π” structure of DAST. The central asymmetry of crystal structures and crystal growth stability will be improved by modifying spatial arrangement design of functional elements. The crystal growing apparatus will be developed coupled with the crystal growth mechanism and the controlling growth of large-size and high-quality crystals will be realized. The THz properties will be tested using optical rectification (OR) and difference frequency generation (DFG) methods and the problem of low efficiency of laser-to-THz wave radiation conversion will be solved by optimizing phase matching. Combining the design of crystal structure, the mechanisms of the main functional elements and their spatial orientation arrangement acted on crystal structure, growth stability and THz performance can be established. New organic terahertz crystals with potential application values will be obtained and independent intellectual property rights will be formed.