Detection of strong light-matter interaction and near-field mapping on a single resonator with a thermal transducer

thin layer of a mid-IR transparent polymer is inserted inside a metallic nano-resonator, where a photonic mode and an intersubband transition are strongly coupled. Acting as a non-perturbative transducer, and without essentially modifying the optical response, the polymer allows the detection of absorbed optical power in the form of thermal expansion due to heat dissipation. This innovative approach permits to identify - at the nano-resonator level - the typical anti crossing characteristic of the polaritonic system, and to perform direct imaging of the electromagnetic fields buried within the optical cavity.