太赫兹量子阱探测器偏振特性研究

Terahertz (THz) quantum-well photodetector have lots of advantages such as small size, stable performance, fast response and selected absorption of the polarized terahertz light. It is an important narrow spectrum detector in 2 to 7 THz region and has significant application prospects in terahertz communication and imaging. In this project, we calculate the polarization extinction ratio of the detector by employing the modal expansion approach to optimize the grating strucure parameters of the detector, and then fabricate the corresponding devices. The Fourier transform spectrometer is used to characterize the polarization photocurrent spectra of the devices with comparable grating parameters. And the polarization extinction ratio acquired from the spectra is analyzed and compared with the calculated value. Direct response to the polarized light is studied by employing the black body and the terahertz quantum-cascade laser as the source, respectively. The experimental results and the calculated values are comparing with each other. Device with the best polarization extinction ratio value is optimized. Finally, based on the linear polarization property of the light from the terahertz laser, the response ability to fast change polarized light is studied via rapidly rotating the polarization film. The possibility of this detector as the fast demodulating device in 2 to 7 THz region can be further confirmed via this applying project, which will provide an experimental basis for the performance demonstration of the fast polarization modulator and developing new terahertz modulating and demodulating methods in the future.

太赫兹（THz）量子阱探测器具有体积小、性能稳定、响应速度快以及对偏振光选择吸收等特点，是2-7 THz频段非常重要的一种窄谱探测器，在THz通信与成像方面具有重要的应用前景。本申请项目拟针对THz量子阱探测器的偏振吸收特性，采用模态扩展方法从理论上对探测器的偏振消光比进行计算，获得最优化光栅结构参数并制备相应的器件；采用傅里叶变换光谱仪测量分析器件的偏振光电流谱和消光比；以黑体辐射源和THz量子级联激光器为光源分别测量器件对偏振光的直接响应，对比实验测量值和理论计算值，优选出偏振消光比最好的器件；利用THz量子级联激光器输出激光的线偏振特性，通过快速旋转偏振片研究THz量子阱探测器对快速变化偏振光的响应能力。通过本申请项目的研究，进一步验证THz量子阱探测器作为2-7 THz频段快速解调器件的可行性，为未来快速偏振调制器性能的实验验证、开发新的THz调制解调手段奠定实验基础。

太赫兹量子阱探测器（THz QWP）是2-7 THz频段非常重要的一种窄谱探测器，它具有结构简单、可靠性高、体积小、响应速度快等特点，由于其独特的低维结构，其对辐射的探测具有偏振选择特性，因此在THz通信与成像方面具有重要应用前景。本项目围绕THz QWP的偏振选择特性，设计并制备了不同占空比的一维金属光栅耦合结构THz QWP，重点研究了器件的偏振光电流谱随光栅结构参数的变化，获得了不同光栅参数下器件的偏振探测消光比，分析了不同探测频点处偏振消光比变化趋势的差异性，结果表明，光栅结构器件中GaAs材料LO声子共振吸收过程具有比峰值探测频率处更好的偏振选择特性；采用Bias Tee信号叠加与放大技术，搭建了基于THz量子级联激光器（QCL）的快速发射接收系统，在国际上率先实现了对0.5 GHz调制THz光的直接探测，开发出对偏振敏感的THz快速探测模块，实现了对水平偏振THz自由电子激光脉冲信号的有效表征，获得用户好评。本项目的研究成果将为研究LO声子共振吸收型THz QWP器件及其在偏振光探测方面的应用提供了很好的实验支撑，同时也为研究基于THz QWP的偏振解调技术、THz椭偏技术，开发相应的应用模块奠定了很好的实验基础。