High-power mid-infrared interband cascade lasers

We have grown and fabricated interband cascade lasers (ICLs) with ``W'' active regions. The ICL structures were etched into 140-$\mu $m-wide ridges, with 100-$\mu $m-wide metal strips deposited in the middle, and operated epitaxial-side-up. Initial devices displayed lasing thresholds as low as 12 A/cm$^{2}$ at 78 K, series resistance as low as 0.21 m$\Omega \cdot $cm$^{2}$, and a voltage efficiency of 96{\%}. Cavity length studies on a series of ICLs with 5, 10, and 15 stages determined that the internal losses at 78 K were 16, 27, and 37 cm$^{-1}$, respectively, while the internal efficiencies were $\approx $ 80{\%} in all cases. Pulsed operating temperatures as high as 300 K were obtained, and a 5-stage device with 0.5 mm cavity length had a wallplug efficiency per facet of $\approx $ 20{\%} without facet coatings. A 3-mm-long laser with high-reflection (95{\%}) and anti-reflection (5{\%}) coatings produced $>$1.1 W of cw output power at 78 K.