Low voltage-defect quantum cascade laser with heterogeneous injector regions.

We demonstrate an In(0.635)Al(0.356)As/In(0.678)Ga(0.322)As strain compensated quantum cascade laser that employs heterogeneous injector regions for low voltage defect operation. The active core consists of interdigitated undoped and doped injectors followed by nominally identical wavelength optical transitions. The undoped injector regions are designed with reduced voltage defect while the doped injectors are of a more conventional design. The measured average voltage defect is less than 79 meV. At 80 K, a 2.3 mm long, back facet high reflectance coated laser has an emission wavelength of 4.7 mum and outputs 2.3 W pulsed power with a peak wall-plug efficiency of 19%.