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Interband cascade lasers with longer wavelengths

While much of the previous work on interband cascade lasers (ICLs) has been limited to the 3-4 μm spectral range, it was recently demonstrated at NRL and elsewhere that the low threshold current and power densities characteristic of ICLs can be extended to longer wavelengths. Here we report on the performance of ICLs operating in the 4.6-6.1 μm spectral range. The pulsed threshold current density at room temperature for an ICL emitting at λ = 4.8 μm is 220 A/cm2, the lowest ever reported for a semiconductor laser at such a long emission wavelength. Broad-area devices emitting in the 4.6-4.9 μm range are observed to maintain pulsed external differential quantum efficiencies (EDQEs) of 11-17% when operating at 375 K. An ICL emitting at λ = 5.7 μm exhibits a threshold current density of 450 A/cm2 and EDQE of 27% at room temperature. The Auger coefficients extracted from these thresholds indicate a systematic increase with wavelength, with the value at 6 μm being 3-4 times higher than that at λ = 3.5 μm.