太赫兹量子级联激光器(THz-QCL)是用于实现自混合干涉的半导体激光器。利用自混合干涉效应,实验测量了THz-QCL频谱、线宽增强因子以及反馈光耦合系数。搭建了THz-QCL自混合干涉光路,基于THz-QCL驱动电压,获得了具有高信噪比的自混合干涉信号及其随反馈光光程变化的曲线。通过对自混合干涉信号进行解析,准确获得了THz-QCL在不同工作电流和温度下的激射频谱,频谱的分辨率反比于反馈光光程的变化。基于自混合干涉信号,分析得到了THz-QCL的线宽增强因子以及反馈光耦合系数。所实现的自混合干涉测量技术有望发展为物质的太赫兹频谱识别和测量技术。

A terahertz quantum cascade laser (THz-QCL) is a kind of semiconductor laser, which is suitable to realize the self-mixing interference. In this work, an experimental method based on self-mixing interference effect is demonstrated for the measurements of the emission spectrum, linewidth enhancement factor, and feedback optical coupling coefficient of a THz-QCL. We set up the optical path for self-mixing interferometry with THz-QCL to obtain the self-mixing interference signal with high signal-to-noise ratio as well as its variance with feedback optical distance, based on voltage driven by THz-QCL. By analyzing the self-mixing interference signal, the lasing spectra of THz-QCL under different operating currents and temperatures are obtained accurately. The resolution of spectra is inversely proportional to feedback optical distance. In addition, we investigate the linewidth enhancement factor of THz-QCL and the feedback optical coupling coefficient based on the self-mixing interference signal. The self-mixing interferometry demonstrated here is expected to be further developed into one used for terahertz spectral identification and measurement.