Interband cascade lasers with high continuous-wave output powers at room temperature

We discuss approaches to increasing the cw output power of the interband cascade lasers (ICLs) for the midwave infrared spectral region. While most of the attention to date has been focused on reducing the operating power of the ICL, the optimization for maximum output power proceeds in a different direction. We find that increasing the number of stage is beneficial, in that it boosts the slope efficiency with only a modest penalty due to higher threshold power density and extra heating. The critical figure of merit for realizing high-power ICLs is the internal loss, which can be estimated from the external differential quantum efficiency (EDQE) per stage. The internal loss can be controlled by varying the thickness of the low-doped GaSb separate-confinement layers (SCLs). We demonstrate room-temperature EDQEs approaching 45% for broad-area 7-stage ICLs with 800-nm-thick SCLs.