Quantum-cascade lasers based on an active region with low sensitivity to thickness fluctuations

The results of the study of ridge quantum-cascade lasers of the 8 $\mu$m spectral range based on the design of the active region with escape from the lower laser level through scattering by a longitudinal optical phonon and subsequent extraction of charge carriers into the injector layers through the miniband are presented. The use of an active region based on 35 periods forming a cascade and the use of InP waveguide claddings with a thickness of $\ge$3.5 $\mu$m, along with the use of additional confining InGaAs layers, made it possible to realize effective heat removal from the active region and a high optical confinement factor ($\sim$68%). Increasing the injector doping level made it possible to realize a peak output optical power of the order of $\sim$3.6 W with a total wall-plug efficiency of about $\sim$6%.