Infrared Scanning Near-Field Optical Microscopy (Ir-Snom) For Thermal Profiling Of Quantum Cascade Lasers

In this work, we present the development of an infrared scanning near-field optical microscope (IR-SNOM) for thermal imaging. As an example, we explore thermal imaging of quantum cascade lasers (QCLs). QCLs are attractive infrared (IR) sources for chemical detection due to their tunability and wide emission range spanning from mid-wavelength to long-wavelength infrared radiation (MWIR and LWIR). However, they require high performance cooling systems and have limited use at low power in continuous wave (CW) operation due to the potential for thermal failure of the device. Thermal imaging can help identify mechanisms and points of failure during laser operation. Because the size of the features of QCLs (similar to 1 mu m) are much smaller than the wavelength of the emitted thermal radiation, IR-SNOM is an ideal technique to image the spatial thermal profile of QCLs during operation to guide design improvement.