Mid-infrared interband cascade lasers with quantum efficiencies >200%

An external differential quantum efficiency exceeding 200% has been observed from 4 μm InAs/InGaSb/AlSb interband cascade lasers under 1 μs pulses and 0.1% duty cycle at 80 K. By increasing the pulse lengths and the repetition rates, average powers >16 mW have been measured with 5 μs pulses at 10% duty cycle, the internal quantum efficiency and the internal loss are determined to be 220% and 14 cm−1, respectively.