Optically pumped mid-infrared type-II W lasers on InAs substrates

The authors report the design, MBE growth, processing and characterisation of mid-infrared type-II W lasers grown on InAs. Optical pumping by a 980 nm laser diode produced CW lasing to 78 K, where the emission wavelength was 3.52 μm. Pulsed operation was observed to 265 K with pumping by a Q-switched 2.1 μm Ho:YAG laser. The differential power conversion efficiency per facet for the 40-period structure was as high as 4.6% at T = 30 K in the CW mode. The threshold at low temperatures was extremely low, e.g. 20 W/cm² at T = 20 K. The characteristic temperature for CW lasing at 10 K < T < 78 K was 26 K, while for pulsed operation in the range T = 78 - 200 K it was 36 K.