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.