Pushing the Room Temperature Continuous-Wave Operation Limit of GaSb-Based Interband Cascade Lasers beyond 6 µm

Abstract

GaSb-based interband cascade lasers (ICLs) emitting at a center wavelength of 6.12 µm at 20 °C in continuous-wave operation up to a maximum operating temperature of 40 °C are presented. Pulsed measurements based on broad area devices show improved performance by applying the recently published approach of adjusting the Ga (Formula presented.) InxSb layer thickness in the active region to reduce the valence intersubband absorption. The W-quantum well design adjustment and the optimization of the electron injector, to rebalance the electron and hole concentrations in the active quantum wells, improved the device performance, yielding room temperature current densities as low as 0.5 kA cm−2 for broad area devices under pulsed operation. As a direct result of this improvement together with optimizations of the waveguide design, the long wavelength limit for GaSb-based ICLs in continuous-wave operation could be extended. For an epi-side down mounted 23 µm wide and 2 mm long device with nine active stages and high-reflectivity back facet, the threshold power is below 1 W and the optical output power is over 25 mW at 20 °C in continuous-wave mode. Such low-threshold and low-power consumption ICLs are especially attractive for mobile and compact sensing systems.