Continuous Wave Quantum Cascade Lasers With Reduced Number of Stages

Experimental data for 15-stage 5.6-μm quantum cascade lasers based on Al
_0.78
In
_0.22
As/In
_0.69
Ga
_0.31
As active region composition are presented. Pulsed slope efficiency, threshold current density, and wall-plug efficiency for a 2.1 mm × 10.4 μm device with a high reflection-coated back facet were measured to be 1.45 W/A, 3.1 kA/cm
²
, and 18%, respectively. Corresponding continuous wave values for the same parameters were measured to be 1.42 W/A, 3.7 kA/cm
²
, and 12%. Demonstrated continuous wave optical power level exceeding 0.5 W per millimeter of cavity length makes quantum cascade lasers with reduced number of stages suitable for high power infrared applications.