Low Threshold, Long Wavelength Interband Cascade Lasers With High Voltage Efficiencies

We report on the substantial advancement of long wavelength InAs-based interband cascade lasers (ICLs) utilizing advanced waveguides formed from hybrid cladding layers and targeting the 10- $12~\mu \text{m}$ wavelength region. Modifications in the hole injector have improved carrier transport in these ICLs, resulting in significantly reduced threshold voltages ( $\text{V}_{\text {th}}$ ) as low as 3.62 V at 80 K. Consequently, much higher voltage efficiencies were observed, peaking at about 73% at $10.3~\mu \text{m}$ and allowing for large output powers of more than 100 mW/facet. Also, low threshold current densities ( $\text{J}_{\text {th}}$ ) of 8.8 A/cm2 in cw mode and 7.6 A/cm2 in pulsed mode near $10~\mu \text{m}$ were observed; a result of adjustments in the GaInSb hole well composition intended to reduce the overall strain accumulation in the ICL. Furthermore, an ICL from the second wafer operating at a longer wavelength achieved a peak voltage efficiency of 57% at $11.7~\mu \text{m}$ , with a peak output power of more than 27 mW/facet. This ICL went on to lase beyond $12~\mu \text{m}$ in both cw and pulsed modes, representing a new milestone in long wavelength coverage for ICLs with the standard W-QW active region.