Surface-Emitting, Monolithic Beam-Combined Mid-Wave IR Quantum Cascade Lasers

The technical objectives of this proposal are: (1) demonstrate a 4.6 micron-emitting grating-coupled surface-emitting (GCSE) quantum cascade laser (QCL) designed for incorporation in an Active-Photonic-Crystal (APC) structure; (2) demonstrate a high-index-contrast APC-QCL edge-emitting structure, designed for incorporation of gratings; (3) demonstrate a GCSE-APC-QCL structure; (4) Develop monolithic aperture-filling optics for GCSE-APC QCLs; (5) demonstrate near-diffraction-limited-beam CW operation to > 15 W power, in the 4.5-micron wavelength range, from GCSE-APC QCLs; (6) Develop a plan for monolithically coherent-power-scaling GCSE-APC QCLs to powers exceeding 100 W CW. Step-taper-active (STA) QCLs will be used in the design since they suppress carrier leakage out of the QCL active regions, resulting in electro-optical characteristics much less temperature sensitive than in conventional QCLs; thus, allowing for significant increases in CW power and wallplug efficiency. The design will be for APC devices of a built-in index step at least an order of magnitude higher than in conventional APC-QCLs, as to achieve stable-beam operation in CW operation to high coherent powers with high wallplug efficiency. For 4.6 micron-emitting devices the goal is to obtain usable CW powers as high as 20 W, delivered in near-diffraction-limited beams.