Type-II mid-infrared lasers

Recent progress towards the realization of high-power, non-cryogenic (quasi-)cw mid-IR lasers based on the "W" configuration of the active region is reported. Type-Il diodes with AlGaAsSb broadened-waveguide separate confinement regions are the first III-V interband lasers to achieve room-temperature pulsed operation at a wavelength longer than 3 mu m. For cw operation, T-max was 195 K and P-out = 140 mW was measured at 77 K. Optically-pumped W lasers recently attained the highest cw operating temperatures (290 K) of any semiconductor laser emitting in the 3-6 mu m range. For a lambda = 3.2 mu m device at 77 K,the maximum cw output power was 0.54 W per uncoated facet. In order to maximize the absorption of the pump in the active region, an optical pumping injection cavity (OPIC) structure was used to create an etalon cavity for the 2.1 mu m pump beam. The pulsed incident pump intensity at threshold was only 8 kW/cm(2) at 300 K for this edge-emitting mid-IR laser. The differential power conversion efficiency was 9% at 77 K and 4% at 275 K, which indicates promising prospects for achieving high cw output powers at TE-cooler temperatures following further optimization.