Room-temperature continuous-wave operation of quantum-cascade lasers at λ∼4μm

Abstract
High-power cw λ∼4μm quantum-cascade lasers (QCLs) are demonstrated. The effect of different cavity length and laser die bonding is also investigated. For a high-reflectivity-coated 11-μm-wide and 4-mm-long epilayer-down bonded QCL, cw output powers as high as 1.6W at 80K and 160mW at 298K are obtained, and the cw operation is achieved up to 313K with 12mW. The laser exhibits a threshold current density of 1.96kA∕cm2, a slope efficiency of 737mW∕A, and a maximum wall-plug efficiency of 0.9% under cw mode at 298K. In pulsed mode, a maximum average power of 552mW at 298K is achieved at 45% duty cycle and a characteristic temperature is 176K from 80to393K.