A strain-balanced, InP-based quantum cascade laser structure designed for light emission at 4.6μm was grown by metal-organic chemical vapor deposition. A maximum total optical power of 1.6W was obtained in continuous-wave mode at 300K for uncoated devices processed in buried heterostructure geometry with stripe dimensions of 5mm by 9.5μm. Corresponding maximum wall plug efficiency and threshold current density were measured to be 8.8% and 1.05kA∕cm2, respectively. Fully hermetically packaged laser of identical dimensions produced in excess of 1.5W under the same conditions.

Published Version

Published Version

Strain-balanced In0.6Ga0.4As/Al0.56In0.44As quantum cascade lasers emitting at a wavelength of 7.1 μm are reported. The active region is based on a three-phonon-resonance quantum design with a low voltage defect of 120 meV at injection resonance. A maximum wall-plug efficiency of 19% is demonstrated in pulsed mode at 293 K. Continuous-wave output power of 1.4 W and wall-plug efficiency of 10% are measured at the same temperature, as well as 1.2 W of average power in uncooled operation. A model for backfilling of the lower laser level which takes into account the number of subbands in the injector is presented and applied to determine the optimum value of the voltage defect to maximize wall-plug efficiency at room temperature, which is found to be ~100 meV, in good agreement with experimental results.

A strain-balanced, Al0.7In0.22As/In0.72Ga0.28As/InP quantum cascade laser structure, designed for light emission at 4.7µm using the non-resonant extraction design approach, was grown by molecular beam epitaxy. Laser devices were processed in tapered buried heterostructure geometry and then mounted on AlN/SiC composite submounts using hard solder. A 10 mm long laser with 7.5µm-wide central section tapered up to 20µm at laser facets generated over 4.5W of single-ended CW/RT optical power at 283K. Maximum wallplug efficiency of 16.3% for this laser was reached at 4W level. Reliability of over 2,000h has been demonstrated for an air-cooled system delivering optical power of 3W in a collimated beam with overall system efficiency exceeding 10%.