On-Chip Passive Phase-Locking for High Coherent Power, Mid-IR Quantum Cascade Lasers

The technical objectives of this proposal are: 1) the design of 8 micron-emitting active-photonic-crystal (APC) quantum-cascade (QC) lasers by using passive phase-locking in a monolithic structure in order to achieve multiwatt-range, diffraction-limited powers; and 2) the development of the key fabrication steps for realizing the proposed APC QC laser. Deep-well (DW) QC lasers will be used in the design since they suppress carrier leakage out of active regions, resulting in electro-optical characteristics much less temperature sensitive than for conventional QC devices; thus allowing for significant increases in average power and wallplug efficiency. At an emission wavelength of 8 microns the estimated increase in average power for a single QC laser is from 0.2 W to 0.5 W. For coherently scaling the power at the chip level, a novel type of APC-type structure is proposed whose elements are DW-QC lasers. The design will be for APC devices of built-in index step an order of magnitude higher than for conventional APC-QC devices, as to achieve stable-beam operation in quasi-CW or CW operation to high coherent powers with high wallplug efficiency. For 8 micron-emitting devices the design will be for usable average powers more than 3 W, delivered in diffraction-limited beams.