Intraband’s Phase II.5 STTR Program achieves coherent single-longitudinal-mode output from a surface-emitting QCL
The achievement of a coherent, single-longitudinal-mode, surface-emitting beam was presented at Photonics West 2020 and published in the SPIE proceedings . While this demonstration realized 150 mW optical output power, ultimately, arrays of surface-emitting QCLs are expected to achieve multi-Watt-range CW, spatially coherent output powers. This work was made possible by a $1M, 2-year extension to the Intraband and University of Wisconsin Madison’s Phase II STTR programs on QCL surface emitters and surface-emitting arrays under the Navy’s Commercialization Readiness Program.
Surface-emitters (SEs) have many advantages over conventional edge-emitters such as potential for improved high-power reliability, as the SEs can be designed to eliminate failure modes originating at cleaved facets; low manufacturing cost, as they can be tested directly on processed wafers without the need to separate chips; and narrower beam divergence due to their larger emitting apertures. Surface-emitters, employing metal-semiconductor diffraction gratings and laterally resonant high-index-contrast photonic-crystal structures, can potentially achieve 15-W average output powers while maintaining single-spatial and single-frequency mode operation.
 J. H. Ryu, C. Sigler, C. Boyle, J. D. Kirch, D. Lindberg, T. Earles, D. Botez, L. J. Mawst, “Surface-emitting quantum cascade lasers with 2nd-order metal/semiconductor gratings for high continuous-wave performance,” Proc. SPIE 11301, Novel In-Plane Semiconductor Lasers XIX, 113011P (24 February 2020); https://doi.org/10.1117/12.2543595