Pushing the room temperature continous-wave operation limit of GaSb-based interband cascade lasers beyond 6 $μ$m

Abstract

We present GaSb-based interband cascade lasers 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. Pulsed measurements based on broad area devices show improved performance by applying the recently published approach of adjusting the Ga1−xInxSb 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 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 9 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 interband cascade lasers are especially attractive for mobile and compact sensing systems.

Enhanced performance of InAs-based interband cascade lasers emitting between 10–13 µm

“…Hence, actual internal losses present in these devices could be substantially higher than the estimated values based only on the free-carrier absorption loss. The extra absorption loss might be caused by intersubband transitions in valence band QWs [27,28], which was recently studied and confirmed in ICLs in the 4-7 µm wavelength region [29,30]. How intersubband transitions in the valence band could affect the device performance of LW InAs-based ICLs would be an interesting topic for future research.…”