High single-mode powers from interband cascade lasers

Mid-infrared interband cascade lasers (ICLs) that operated in continuous-wave (cw) mode at temperatures up to 62°C have been previously demonstrated. However, spectroscopic applications such as gas sensing also require emission into a single spectral mode that can be tuned over a wide wavelength range by varying the injection current and/or temperature. A step in that direction is this report of an ICL with a corrugated distributed feedback (DFB) pattern etched into the ridge sidewalk. The corrugations serve the dual purpose of suppressing higher-order lateral modes by increasing their loss, while also providing distributed feedback. The present work reports cw operation to 72°C, and also broad-area devices displaying pulsed threshold current densities as low as 375 A/cm² at 27°C. The characterization of a series of narrow ridges with widths ranging from 3.2 to 15.1 μm confirmed that the degradations of threshold current density and differential slope efficiency were modest for widths down to 5.1 μm. The 11.1 and 13.0-μm-wide uncoated ridges produced up to 45 mW per facet of cw power at 20°C, and displayed maximum wallplug efficiencies of 3.5% per facet.