Progress in development of room temperature CW GaSb based diode lasers for 2-3.5 μm spectral region

Recent progress and state of GaSb based type-I lasers emitting in spectral range from 2 to 3.5 μm is reviewed. For lasers emitting near 2 μm an optimization of waveguide core width and asymmetry allowed reduction of far field divergence angle down to 40-50 degrees which is important for improving coupling efficiency to optical fiber. As emission wavelength increases laser characteristics degrade due to insufficient hole confinement, increased Auger recombination and deteriorated transport through the waveguide layer. While Auger recombination is thought to be an ultimate limiting factor to the performance of these narrow bandgap interband lasers we demonstrate that continuous improvements in laser characteristics are still possible by increasing hole confinement and optimizing transport properties of the waveguide layer. We achieved 190, 170 and 50 mW of maximum CW power at 3.1, 3.2 and 3.32 μm wavelengths respectively. These are the highest CW powers reported to date in this spectral range and constitute 2.5-fold improvement compared to previously reported devices.