Battery-operated mid-infrared diode laser frequency combs

Mid-wave infrared (MIR, 3–5 μm) optical frequency combs (OFC) are of critical importance for spectroscopy of fundamentalmolecular absorption features in space and terrestrial applications. Although in this band OFCs can be generated via supercontinuumor difference frequency generation using optical pumping schemes, unprecedented source miniaturizationand monolithic design are unique to electrically-pumped semiconductor laser structures. To date, high-brightness OFCgeneration in this region has been demonstrated in quantum- and interband cascade lasers (QCL/ICL), yet with sub-optimalspectral properties. Here, we show the first MIR quantum well diode laser (QWDL) OFC, whose excellent spectral uniformity,narrow optical linewidths, and milliwatt optical power are obtained at a fraction of a watt of power consumption. Asa proof-of-principle, we show a directly-battery-operated MIR dual-comb source with almost 0.5 THz of optical coverageat 3.04 m obtainable in microsecond timescales. These results indicate the high suitability of QWDL OFCs for futurechip-based real-time sensing systems in the mid-infrared.