Multiwatt long wavelength quantum cascade lasers based on high strain composition with 70% injection efficiency.

A strain-balanced, AlInAs/InGaAs/InP quantum cascade laser structure, designed for light emission near 9 µm, was grown by molecular beam epitaxy. Laser devices were processed in buried heterostructure geometry. Maximum pulsed and continuous wave room temperature optical power of 4.5 and 2 W and wallplug efficiency of 16% and 10%, respectively, were demonstrated for a 3mm by 10 µm laser mounted epi-side down on an AlN/SiC composite submount. Pulsed laser characteristics were shown to be self-consistently described by a simple model based on rate equations using measured 70% injection efficiency for the upper laser level.