Widely Tunable Mid-Wave Infrared Surface Emitting Lasers for Wide Angle Beam Steering

This Small Business Innovation Research Phase I project aims at monolithically integrating high power edge emitting continuous wave (cw) quantum cascade lasers (QCLs) with waveguides and surface emitting sub-wavelength gratings in silicon-on-sapphire (SoS) enabling 70 percent surface emission of emitted QCL light and narrow beam wide angle 55 degrees by 20 degrees two-dimensional (2D) beam steering between 4-5micron wavelength range. Conventional surface emission with second order metallized gratings, photonic crystal gratings, buried gratings, and ring cavities have complexities in design and fabrication that need to be overcome to achieve high cw surface emission. Furthermore, wide angle 2D beam steering needs minimum element spacing of the order of wavelength which will be challenging to achieve when combined simultaneously with high power requirement. In our method, an edge emitting QCL is bonded to a SoS wafer. High intensity cw emission from demonstrated cw edge-emitting QCLs is completely evanescently coupled to demonstrated silicon waveguides in SoS and emitted from the surface using demonstrated mid-infrared sub-wavelength gratings in SoS. 2D wide angle beam steering can be achieved by wavelength tuning the multiple evanescently coupled DFB QCLs to silicon integrated waveguides, and phase shifting via thermal tuning, as demonstrated.