High-Power Operation of Uncoated Strain-Compensated Quantum Cascade Lasers at 4.8μm

High-power operation of uncoated 22-μm-wide quantum cascade lasers (QCLs) emitting at λ≈4.8μm is reported. The emitting region of the QCL structure consists of a 30-period strain-compensated In_0.68Ga_0.32As/In_0.37Al_0.63As superlattice. For a 4-mm-long laser in pulsed mode, a peak output power is achieved in excess of 2240mW per facet at 81K with a threshold current density of 0.64kA/cm². The effects of varying the cavity lengths from 1 to 4mm on the performances of the QCLs are analysed
in detail and the low waveguide loss of only about 1.4cm^-1 is extracted.