Tunable characteristic of phase-locked quantum cascade laser arrays* *Project supported by the National Basic Research Program of China (Grant Nos. 2018YFA0209103 and 2018YFB2200504), the National Natural Science Foundation of China (Grant Nos. 61991430, 61774146, 61790583, 61674144, 61774150, and 61805168), the Beijing Municipal Science & Technology Commission, China (Grant No. Z201100004020006), and the Key Projects of the Chinese Academy of Sciences

Abstract

A multimode interference (MMI) structure is designed to simplify the fabrication of quantum cascade laser (QCL) phase-locked arrays. The MMI geometry is optimized with a sufficient output channel distance to accommodate conventional photolithography and wet etching process by which power amplifier array is fabricated without using the complicated two-step etching-regrowth or dry etching technique. The far-field pattern with periodically modulated peaks reveals that the beams from the arrays are phase-locked. Furthermore, the frequency tuning performance of the MMI-based phase-locked arrays is studied using the Littrow-configuration external cavity structure. A wavelength tuning range of more than 60 cm−1 is demonstrated, which will eventually realize the high power, frequency tunable, large-scale phase-locked arrays, and their application in spectroscopy.