非线性有机材料DAST的研究及应用

随着光通信、光信息处理技术等的快速发展，非线性光学材料越来越受到学术界与工业的关注。与无机非线性光学材料相比，有机非线性光学材料具有响应时间短、易于加工和高非线性系数等优点。其中，4-(4-二甲氨基苯乙烯基)甲基吡啶对甲苯磺酸盐(DAST)是人工设计的一种具有非中心对称性和较强极化率的有机非线性材料。大量理论和实验结果表明，DAST具有高二阶光学非线性系数、高电光系数、大双折射率差和低介电常数等特性，能够产生更快、更强的光学非线性响应，还具有优异的太赫兹波发射及吸收性能，是目前综合性能最优、应用最广、最具研究价值的非线性有机材料。近年光谱研究显示，DAST还表现出各向异性的太赫兹光谱特性。文章系统地总结了DAST晶体在太赫兹波发射、二次谐波产生、电光探测和电光调制等众多领域的国内外研究成果，还概括了我们团队近期在DAST基薄膜、太赫兹光谱、光电特性、超材料等新领域的研究进展。此外，还提出将准相位匹配法用于DAST晶体研究、利用电场或自组装膜诱导生长DAST晶体等新思路。对DAST成果的总结和梳理，将促进非线性DAST有机材料在电光调制器、频率转换器、THz探测器等重要领域的应用与理论研究，使其能够更加广泛地应用在光通信、光信息处理、军事技术等重要领域。

Studies and Applications of Organic Nonlinear Material DAST

With the rapid development of optical communication and optical information processing technology, nonlinear optical materials have attracted considerable attention in both industry and academia. Compared with inorganic non-linear optical materials, organic nonlinear optical materials exhibit the advantages of short response time, easy processing, and high nonlinear coefficient. Particularly, 4-N, N-dimethylamino-4’-N’-methyl-stilbazolium tosylate (DAST) is an artificially-designed organic non-linear material with non-centrosymmetry and strong polarizability. Numerous theoretical and experimental results indicated that DAST is one of the most important and successful organic nonlinear materials. Owing to its high second-order optical nonlinear coefficient, large electro-optic coefficient, large birefringence difference, and low dielectric constant, faster and stronger optical nonlinear responses can be achieved by DAST. Recent spectroscopic results revealed that DAST exhibits anisotropic THz spectral features. In this article, the growth of DAST crystals, and their practical applications in THz wave generation, second harmonic generation, as well as electro-optical detection and electro-optical modulation, are systematically reviewed. Moreover, our recent results about the preparation of DAST-based composite films, THz spectra, optoelectronic properties of DAST modified by carbon nanotubes or graphenes, and novel DAST-based metamaterials, are simultaneously presented. These results suggest a new perspective on DAST and its potential applications in the future. In addition, we have proposed some new ideas about DAST, such as DAST crystal growth induced by an electric filed or self-assembling monolayer, and frequency conversion efficiency of DAST crystal improved by quasi-phase-matching method. The DAST results systematically summarized in this review are helpful for promoting further studies on DAST-based materials and their applications in electro-optic modulators, THz detectors, frequency converters, etc, and consequently, the applications of DAST in optical communications, optical information processing, military technology and other important fields can be further expanded.