High-performance interband cascade lasers for λ = 3-5.5 µm

We report that various recent design modifications and optimizations have produced significant advances in the performance of interband cascade lasers (ICLs) for the mid-IR spectral band. Figure 1 illustrates the progression with time of ICL pulsed threshold current densities, as compared to some of the lowest reported results for quantum cascade lasers. All of the ICL devices were standard 150-μm-wide broad-area ridges with 2 mm cavity lengths. Note that thresholds for all of the latest generation of ICL designs (labeled Gen3) decreased substantially, to the 170-260 A/cm² range. Figure 2 shows threshold power densities (P_th = current density × voltage) as a function of wavelength for the last four generations of 5-stage devices. Note that the Gen3 power densities are substantially lower than any of the earlier results, and that they fall below the dashed curve corresponding to probable room-temperature cw operation at wavelengths as long as 5.5 μm.