On-chip wavelength beam combined DFB quantum cascade laser arrays.

Quantum cascade lasers (QCLs) are essential for a wide range of mid-infrared (mid-IR) applications. Achieving wavelength beam combining (WBC) of QCLs on a chip scale is highly desirable for power scaling and/or broadband emission multi-wavelength output while maintaining a single output beam. We propose a straightforward architecture that monolithically integrates five distributed feedback (DFB) QCLs with an arrayed waveguide grating (AWG), using III-V semiconductor waveguides. The AWG channel wavelengths are carefully designed to align with the corresponding DFB emissions. An amplifier is also incorporated at the output to boost the total power. After the deposition of anti-reflection coatings on the output facet, the best-performing laser element achieved a peak power of 3 W under pulsed operation, with at least 1.75 W from the other channels. These results mark a significant step toward the realization of on-chip high-power WBC QCLs.