Localized Facet Joule Heating of Mid-infrared Quantum Cascade Lasers

The self-heating or so-called joule-heating effect is detrimental for mid-infrared quantum cascade lasers (MIR QCLs), especially when a high-power electrical current is injected. In this abstract, strong localized heat confinement is observed on the laser facet within a small region between the electroplated gold (EP-Au) layer and the air interface located on the top of the ridge waveguide by employing spatially resolved time-domain thermoreflectance (SR-TDTR) microscopy. In addition, hot spots are clearly observed on this EP-Au layer close to the laser facet due to the imperfect facet cleaving. These results shed light on the significance and improvement of the MIR QCLs thermal management.