Heating Dynamics of Pulse-Pumped Quantum-Cascade Lasers

Measuring the active area temperature is reported as indispensable method for increasing reliability and performance as well as for failure analysis of all semiconductor devices [1] . For quantum-cascade lasers (QCLs), temperature control seems to be of special importance due to higher operating voltages and lower efficiency leading to increased heat generation comparing to laser diodes. For all semiconductor lasers, non-contact methods such as thermoreflectance [2] and interferometry [1] seem to be the most wide-spread due to the possibility of combination of mK-scale temperature and sub-μm spatial resolution without any special modification of the object. However, thermoreflective and interferometric heating measurements are limited to the surface and proved to be well-suited for visualizations of the temperature distributions only at the laser facets and allow little room for study of the in-depth temperature distribution inside the analyzed device. Also, study of heating dynamics at nanosecond scale with these methods seems to be cumbersome [3] .