Gain and Losses and Room-Temperature Operation in Interband Cascade Lasers

Interband cascade laser structures with a different number of cascades and doping types and levels in the separate confinement and in the hole-injection regions were grown. The temperature dependence of the gain and loss coefficients was measured. Although the gain dropped appreciably with increasing temperature, the internal losses remained nearly constant. Internal losses as low as 4.8 cm^-1 were measured at room temperature in an optimized design. Internal quantum efficiency per cascade of 86% is achieved at 240 K. Room-temperature CW operation with a front facet output power of 42 mW was obtained in a 5-cascade structure with a 54% reduced size injection region. The laser operated at 3.8 μm.