American Institute of Physics, Applied Physics Letters, 13(120), p. 131102, 2022
DOI: 10.1063/5.0081817
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Super-resolution microscopy in the visible is an established powerful tool in various disciplines. In the long-wave infrared (LWIR) spectral range, however, no comparable schemes have been demonstrated to date. In this work, we experimentally demonstrate super-resolution microscopy in the LWIR range ([Formula: see text]m) using IR-visible sum-frequency generation. We operate our microscope in a wide-field scheme and image localized surface phonon polaritons in 4H-SiC nanostructures as a proof-of-concept. With this technique, we demonstrate an enhanced spatial resolution of [Formula: see text], enabling to resolve the polariton resonances in individual sub-diffractional nanostructures with sub-wavelength spacing. Furthermore, we show that this resolution allows us to differentiate between spatial patterns associated with different polariton modes within individual nanostructures.