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

TL;DR

This paper demonstrates GaSb-based interband cascade lasers operating at 6.12 μm in continuous-wave mode up to 40°C, with improved design enabling low threshold power and high efficiency suitable for portable sensing applications.

Contribution

The study introduces a novel device design and optimization approach that extends the continuous-wave operation limit of GaSb-based ICLs beyond 6 μm at room temperature.

Findings

Continuous-wave operation at 6.12 μm up to 40°C.

Threshold power below 1 W at 20°C.

Optical output power over 25 mW at 20°C.

Abstract

We present GaSb-based interband cascade lasers emitting at a center wavelength of 6.12 $\mu$m at 20$^\circ$C in continuous-wave operation up to a maximum operating temperature of 40$^\circ$C. Pulsed measurements based on broad area devices show improved performance by applying the recently published approach of adjusting the GaInSb 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 $\mu$m 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$^\circ$C in continuous-wave mode. Such low-threshold and low-power consumption interband cascade lasers are especially attractive for mobile and compact sensing systems.