基于光电导天线探测的THz-ATR 系统设计和性能研究

Design and performance study of THz-ATR system based on photoconductive antenna detection

本文设计并搭建了一种基于光电导天线探测的太赫兹衰减全反射(THz-ATR)系统为痕量低浓度生化大分子水溶液传感检测做准备。不同于THz-TDS测试时太赫兹波与被测样品直接接触,THz-ATR系统利用在发生全反射的界面产生的倏逝波进行检测来避免检测时水溶液对太赫兹波的强吸收作用。系统太赫兹光由飞秒光激发砷化铟产生,探测使用半球硅透镜的光电导天线来延后时域光谱中的回波,从而获得高频谱分辨率。对搭建好的THz-ATR系统进行了性能测试,其频率范围为0.2-2THz,动态范围优于50 dB,信噪比为600:1,频谱分辨率可以达到3 GHz。最后探究了不同湿度环境下的光谱特性,为后续实验提供支持。

In this paper,a terahertz attenuated total reflection(THz-ATR)system based on photoconductive antenna detection was designed and built to prepare for the sensing and detection of trace and low-concentration biochemical macromolecular aqueous solutions.Unlike the THz-TDS test,where the terahertz wave is in direct contact with the sample,the THz-ATR system uses the evanescent wave generated at the interface where total reflection occurs to avoid the strong absorption of terahertz waves by the aqueous solution during the test.The system terahertz light is generated by femtosecond light excited by indium arsenide,which detects a photoconductive antenna using a hemispherical silicon lens to delay echoes in the time-domain spectrum,resulting in high-frequency spectral resolution.The performance of the built THz-ATR system was tested,and its frequency range was 0.2-2 THz,the dynamic range was better than 50 dB,the signal-to-noise ratio was 600:1,and the spectral resolution could reach 3 GHz.Finally,the spectral characteristics of different humidity environments were explored to provide support for subsequent experiments.