Mid-Infrared Frequency Comb from a Ring Quantum Cascade Laser

Abstract

Frequency combs based on quantum cascade lasers (QCLs) are very attractive for dual comb spectroscopy, with continuous improvement in their performance. Average powers of ∼1 Watt and frequency coverage over 100 cm−1 have been demonstrated. Despite the significant improvement in their performance, QCL-based frequency combs still suffer the instabilities within the QCL cavity [1]. Among them, spatial hole burning (SHB) effect is speculated to play an important role in destabilizing the comb operation [2]. However, due to the intrinsic standing wave nature of the Fabry-Pérot (F-P) cavity, effectively eliminating the SHB effect poses a major challenge. Therefore, new cavity structures are needed to solve the problem.