Interband Cascade Lasers With Low Threshold Powers and High Output Powers

The midwave infrared interband cascade laser (ICL) can operate at threshold power densities 30 times lower than those of the quantum cascade laser. This is ultimately attributable to the much longer interband carrier lifetime, rather than to specifics of the cavity dimensions and mirror reflectivities. The ICL is therefore an attractive candidate for insertion into the portable, battery-powered chemical sensors now being developed for this spectral region. We review the characteristics of ICLs operating at wavelengths from 2.9 to 5.5 μm, and show that their Auger coefficients vary by less than a factor of 3 throughout this range. Consequently, the ICL performance degrades only modestly with increasing wavelength. We report that an epitaxial-side-down-mounted ICL ridge of width 30 μm and λ = 3.7 μm emits more than 300 mW of continuous wave (CW) output power at room temperature with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ≤ 3.1. A distributed-feedback ICL with a fourth-order grating etched into its corrugated sidewalls produces 55 mW of CW power in a single spectral mode at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> = 25 °C.