针对太赫兹量子级联激光器光频梳射频信号提取与传输存在的阻抗不匹配问题，设计并提出了一种输入阻抗为20 Ω、输出阻抗为50 Ω的渐变微带线结构，研究了该结构的准TEM模电场分布，并根据S参数建立了相应的LC等效电路模型分析其物理机理。实验中，将渐变微带线结构应用于太赫兹量子级联激光器光频梳射频信号提取与测试，以验证渐变微带线传输射频信号效果，成功测量得到太赫兹量子级联激光器重复频率，其线宽为3.7 kHz，信噪比达到60 dB，在注入电流为700~900 mA范围内重复频率表现为稳定的单模信号，测量得到的最大保持和幅度艾伦方差结果同样表现出重复频率的稳定性。实验结果表明，所设计的渐变微带线具有良好的阻抗匹配效果，能够实现对太赫兹量子级联激光器光频梳射频信号稳定的提取和传输。

太赫兹量子级联激光器（THz QCL）双光梳在光谱检测、测距、成像等领域具有重要应用。双光梳信号严重依赖THz耦合光功率。利用THz QCL激射光为线偏振光的特性，在双光梳光路上插入线偏振片，通过旋转偏振片以达到对THz光强进行调节的作用。系统研究了THz QCL双光梳谱和功率与偏振角度的依赖关系，为实现高稳定THz双光梳光源与应用奠定基础。

We demonstrate the electrical beat note analysis and radio frequency (RF) injection locking of a continuous wave (cw) terahertz quantum cascade laser (QCL) emitting around 3 THz (～100 μm). In free running the beat note frequency of the QCL shows a shift of ～180 MHz with increasing drive current. The beat note, modulation response, injection pulling, and terahertz emission spectral characteristics in the different current regimes I, II, and III are investigated. The results show that in the current regime I close to the laser threshold we obtain a narrower beat note and flat response to the RF modulation at the cavity round trip frequency. The pulling effect and spectral modulation measurements verify that in the current regime I the RF injection locking is more efficient and a robust tool to modulate the mode number and mode frequency of terahertz QCLs.