Corrugated-sidewall interband cascade lasers with single-mode midwave-infrared emission at room temperature

We report interband cascade lasers operating in a single spectral mode $(λ≈3.6μm)$ at $−5–30°C$⁠. A corrugated pattern etched into both sidewalls of the 6- and $9-μm$-wide ridges serves to suppress higher-order lateral modes by increasing their loss, and also provides a fourth-order distributed-feedback grating for longitudinal mode selection. Despite the grating’s weak coupling strength, the $9μm$ ridge produced up to 12 mW per facet of single-mode cw output power at $25°C$⁠, with a side-mode suppression ratio of $>30dB$⁠.