Mid-infrared distributed-feedback interband cascade lasers with continuous-wave single-mode emission to 80 °C

We report continuous-wave (cw) distributed-feedback interband cascade lasers operating in a single spectral mode (λ = 3.7-3.8 μm) at temperatures between 20 and 80 °C. The first-order gratings were realized by patterning high-index germanium layers on top of narrow ridges with relatively thin top claddings. One device generated over 27 mW of cw single-mode output at 40 °C, with a side-mode-suppression ratio >30 dB, while at 80 °C it still emitted >1 mW. At 20 °C, a second device lased in a single spectral mode with <100 mW of drive power. The tuning range was 21.5 nm with temperature and 10 nm with current.