Fascinating and impressive innovations in infrared (IR) analytics have been put forth in the recent years. In this context, exceptional developments in IR laser technology such as e.g. quantum cascade lasers (QCLs), dual comb or super continuum sources enable a new generation of IR methods with outstanding analytical and sensing possibilities. Spectroscopic methods from the classical IR techniques to the more advanced ones, like photothermal, microscopic or ellipsometric instruments have been taken forward. For sensitive ellipsometric far-field mid-IR imaging, lateral resolutions down to the 100 µm range are achieved so far. The work of Alexander Ebner et al. represents a significant improvement of such resolution, down to the diffraction-limit. The article launches a QCL-based micro-ellipsometric set-up using a photoelastic modulator and a read-out with a boxcar integrator, with the possibility of hyperspectral scanning at spatial resolutions better than 13.3 µm, with the laser wavelength being tunable in the 9 to 11 µm range. Compared to related FTIR-techniques the device allows measurement times reduced by a factor of 60000 at excellent noise performance. These specific advantages enable sensitive hyperspectral experiments in reasonable measurement times, which fulfils multiple current requirements in catalysis, bioanalytics, material and environmental research. In particular, complementary hyperspectral amplitude- and phase-related ellipsometric images can be analyzed with respect to chemical and structural properties and their inhomogeneities.

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