Spectral beam combining of discrete quantum cascade lasers

In this paper, we report a spectral beam combining technique based on discrete quantum cascade lasers at l~ 4.8 mm. Good beam qualities of M 2 < 1.3 for both fast and slow axes are obtained. The entire spectrum span is approximately 29.1 cm -1 , which is consistent with the theoretical results of grating equation. Maximum beam combining efficiency of 58.9% with output power exceeding 1 W is demonstrated under continuous wave operation at room temperature. The limit of beam combining efficiency is theoretically investigated. The independent temperature control for the discrete lasers circumvented the issue of thermal crosstalk between the lasers on an array and pave the way to high power and high efficiency laser spectral beam combining.