Very High Average Power Quantum Cascade Lasers by GasMBE

Very high average power QCLs are demonstrated within the 5.8-9 μm wavelength range. At longer wavelengths, scaling of the power is demonstrated by increasing the number of emitting regions in the waveguide core. At λ=9 μm, over 3.5 W of peak power per facet has been demonstrated at room temperature for a single 25 μm by 3 mm diode, with an average power of 150 mW at 6% duty cycle. At shorter wavelengths, highly strain-balanced heterostructures are used to create a high conduction band offset and minimize leakage current. At λ=6 μm, utilizing a high reflective coating and epilayer-down mounting of the laser, we demonstrate 225 mW of average power from a single facet at room temperature. Increasing the conduction band offset further and optimizing the doping in the injector region has led to demonstration of >250 mW average power (λ=5.8 μm) at >50 % duty cycle for a 20 μm by 2 mm HR coated diode bonded epilayer-down to a copper heatsink. Also at room temperature, use of Au electroplating and wider ridges has allowed us to further demonstrate, without epilayer-down bonding, 0.67 W average power at 17% duty cycle from a single 40 μm by 2 mm HR coated laser.