Low threshold InAs-based interband cascade lasers with room temperature lasing wavelengths near 4 and 4.4 <b> <i>μ</i> </b>m

Abstract

Mid-infrared laser spectroscopy at wavelengths of 4–5 μm is important for the detection of greenhouse gases, including CO2 at 4.23 μm, N2O at 4.45 μm, and CO at 4.60 μm, with ultra-high sensitivity and selectivity. It can be used in environmental monitoring, real-time industrial process controls, medical diagnosis/therapeutics, and other applications. In this work, we report significant advances in interband cascade lasers (ICLs) with the shortest emission wavelengths among InAs-based ICLs at room temperature (RT). Benefiting from the precise control of the growth parameters in molecular beam epitaxy, ICL structures were epitaxially grown on InAs substrates with high-quality that is validated by a low threshold current density of 1.9 A/cm2 at 80 K. By minimizing the Urbach tail absorption loss in InAs with excellent material quality, broad-area (BA) devices emitting at 4.02 μm in pulsed operation are demonstrated at 300 K with a threshold current density of 232 A/cm2, which is the lowest among the InAs-based ICLs. These BA devices were able to operate with a maximum voltage efficiency of 89% at temperatures up to 258 K in the continuous wave (cw) mode and to 378 K in the pulsed mode, indicating improved thermal dissipation and a sufficient temperature range for narrow ridge devices to achieve cw operation at RT and above. These demonstrated device features suggest high potential of low-cost InAs-based ICLs for real-world applications in a wide mid-infrared wavelength region.