We report the operation of a III-V interband laser at a wavelength beyond 5 μm and temperatures above 90 K. The active region consists of a strain compensated broken gap four layer superlattice of InAs/Ga0.6In0.4Sb/InAs/Al0.3Ga0.42In0.28As0.5Sb0.5 grown by molecular beam epitaxy. The maximum operating temperature under 2.01 μm pulsed optical excitation was 185 K at a wavelength of 5.2 μm. The peak pump intensity at the 80 K threshold was 62 kW/cm2, and the characteristic temperature (T0) of the threshold intensity was 37 K. This T0 is comparable to the best observed values for 3–4.5 μm lasers based on the InAs/GaInSb material system.

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We show how temporally and spatially resolved lasing spectra may be interpreted to obtain quantitative information on the lattice temperature and refractive index distribution in an optically pumped GaInAsSb/AlGaAsSb quantum well 1.8 μm midwave-infrared laser. We present this technique as a method for evaluating and comparing high power laser structures in terms of optical and thermal efficiency. We also suggest how this method might provide insight into the particulars of filamentation and heat transport in both electrically and optically pumped structures.