Sb-based interband cascade lasers to cover the 3–5 μm spectral window

Semiconductor laser sources for the critical 3–5 um spectral range are evolving and improving rapidly, with significant advancements reported within the last year for three fundamentally different approaches: the intersubband quantum cascade laser (QCL),¹ the type-I quantum well (QW) diode laser,² and the interband cascade laser (ICL).³ Of these three, the most promising candidate to cover the entire wavelength range is the antimonide-based type-II ICL as designed and grown at the Naval Research Laboratory (NRL). Broad area devices have already demonstrated threshold power densities (Pth = current density × voltage) which will enable room temperature (RT) continuous-wave (CW) operation from 2.9 out to 4.6 μm (Fig. 1). The ICL architecture appears uniquely poised not only to offer complete spectral coverage (3–5 μm) but also to operate with low power dissipation. Some of the most recent ICLs display Pth < 0.4 kW/cm² at 300 K (λ ∼ 3.6–4.0 μm), which is more than 20 times lower than the best Pth reported to date for QCLs operating at the same temperature. For this reason, the ICL approach is favored for applications demanding low power and excess heat dissipation, e.g., for long battery lifetimes in the field.