基于DSTMS和OH1有机晶体的超宽带太赫兹辐射源及其偏振调控技术的研究

Terahertz (THz) generation based on difference frequency generation (DFG) in organic crystals, is one of the most efficient ways for ultrawidely tunable (0.5-20 THz) and polarization controllable THz sources, which are key devices for THz applications such as biomedical diagnosis, chemical and physical analysis to the substances. The organic crystals utilized in this method possess large second-order nonlinear susceptibilities, wide range satisfying phase-matching condition, small absorption index in the ultrawide THz frequency range, as well as outstanding electro-optical modulation characteristics, etc. As a result, limited by the effective growing method of the organic crystals, there are very few practical organic materials available. More importantly, the output power and the tunability in the ultrawide frequency range for the THz sources are not satisfying by the performance of the organic nonlinear crystals, and the research of polarization modulation for THz wave in the ultrawide frequency range is still in blank. In this program, two new kinds of organic crystals, DSTMS together with OH1, will be adopted complementally in terahertz generation. Contributed to that, the ultrawidely tunable, output stable, polarization controllable and narrow linewidth monochromic THz sources which are compact and portable, are expected through studying the growing mechanism for high-quality organic nonlinear crystals, exploring the phase-matching condition of DFG in the ultrawide THz frequency range, as well as the electro-optical modulation mechanism of the polarization in the ultrawide THz frequency range. The achievements will lay the foundation for high-resolution THz spectroscopy and imaging applications such as material identifying, multispectral imaging and biomedical diagnosis, etc.

超宽带（0.5-20THz）太赫兹（THz）辐射源是生物医学、物质物理化学光谱分析等应用领域的关键器件，基于有机非线性晶体是实现上述THz辐射源最有效的方法之一。该方法应用的有机非线性晶体不仅具有非线性系数高、相位匹配带宽宽、太赫兹波吸收系数小的特点，还有优良的电光调控特性，目前受限于有机晶体的生长技术,高性能有机非线性材料少，相应THz源的输出能量以及调谐范围也不理想，而其偏振调控特性处于研究空白。本项目拟结合利用新型有机非线性晶体DSTMS和OH1差频产生超宽带太赫兹波，通过研究高性能有机非线性晶体生长机理，探索双晶体补偿超宽带准单色赫兹波相位匹配技术以及有机非线性晶体电光偏振调控的方法，最终实现结构简单紧凑的超宽带范围内连续可调谐、输出补偿的准单色窄线宽偏振可调控的太赫兹辐射源，为在物质鉴定分析、多光谱成像以及生物医学诊断等领域的高分辨率THz光谱及成像技术应用奠定基础。

针对当前物质鉴定分析、多光谱成像以及生物医学诊断等领域中对于高分辨率太赫兹光谱及其成像技术的应用需求，申请人在光学太赫兹辐射源已有研究基础上，提出了基于DSTMS晶体和OH1晶体等新型有机晶体的超宽带太赫兹辐射源及其偏振调控技术研究。通过研究并优化有机晶体的生长方法，生长出大尺寸、高质量的DAST晶体、DSTMS晶体和OH1晶体。搭建了基于有机晶体的超宽带可调谐太赫兹辐射源，调谐范围达到0.3-19.6THz，最高输出单脉冲能量达到μJ量级。开展了基于有机晶体的双折射特性及电光效应特性的偏振调控研究。研究了基于有机晶体的超宽带太赫兹辐射源在光谱测量中的应用。本研究对于促进太赫兹辐射源在物质鉴定分析、多光谱成像以及生物医学诊断等领域中的应用具有重要的推动作用。