Continuous Wave Quantum Cascade Lasers With Reduced Number of Stages

Abstract

Experimental data for 15-stage 5.6- $\mu \text{m}$ quantum cascade lasers based on Al0.78In0.22As/In0.69Ga0.31As active region composition are presented. Pulsed slope efficiency, threshold current density, and wall-plug efficiency for a $2.1~\text {mm} \times 10.4~\mu \text{m}$ device with a high reflection-coated back facet were measured to be 1.45 W/A, 3.1 kA/cm2, and 18%, respectively. Corresponding continuous wave values for the same parameters were measured to be 1.42 W/A, 3.7 kA/cm2, 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.