上海科技大学知识管理系统

Optical feedback is a simple and effective method for tuning laser performance and inducing non-linear dynamics. In this work, we investigate the frequency comb behavior of a terahertz (THz) quantum cascade laser (QCL) under short external cavity optical feedback. A rate equation model is employed to examine the impact of feedback on the spectral linewidth. Numerical simulation indicates that the spectral linewidth is sensitive to the initial phase at high feedback ratios, and the linewidth can be either reduced or broadened. While low feedback ratios lead to a slight increase in linewidth. In the experiment, we reveal that the inter-mode beatnote frequency and its stability vary periodically as the initial feedback phase is changed. Compared to the free-running case without optical feedback, the stability improvement of the inter-mode beatnote signal is clearly observed under certain feedback conditions, which was not experimentally observed for THz QCLs under optical feedback with long external cavities.