Large cavity quantum cascade lasers with InP interstacks

Multicore quantum cascade lasers with large cavities show low optical losses, high saturation intensity, and low beam divergence. We present a four active core laser based on InGaAs-AlInAs material system emitting at 10.5 mu m. To improve thermal conductance, InP interstacks were used to separate active regions. Selective lateral etching of the active regions was used to reduce optical losses. Peak powers up to 4.6 W, average powers up to 310 mW, and wall-plug efficiencies up to 4.6% were measured at 300 K. A far field with full width at half maximum of 18.7 degrees and 49.8 degrees in the lateral and in the growth direction, respectively, was observed.