High-power (λ∼9 μm) quantum cascade lasers

High-power quantum cascade lasers emitting at lambda>9 mum are demonstrated. Accurate control of layer thickness and interfaces is evidenced by x-ray diffraction. Excellent peak power for uncoated lasers, up to 3.5 W per facet for a 25 mum emitter width, is obtained at 300 K for 75 period structures. The threshold current density at 300 K is only 1.4 kA/cm2. From 300 to 425 K, the laser exhibits a characteristic temperature, T-0, of 167 K. Over 150 mW of average power is measured per facet for a duty cycle of 6%. Simulation of the average power output reveals a thermal resistance of 12 K/W for epilayer-up mounted ridges. (C) 2002 American Institute of Physics.