Amplitude- and Phase-Resolved Infrared Nanoimaging and Nanospectroscopy of Polaritons in a Liquid Environment

Polaritons allow for strong light-matter coupling and highly sensitive analysis of (bio)chemical substances processes. Nanoimaging the polaritons’ evanescent fields is critically important experimental mode identification field confinement studies. Here we describe two setups polariton nanoimaging spectroscopy in liquid. We first demonstrate mapping localized plasmon polaritons metal antennas with a transflection infrared scattering-type scanning near-field optical microscope (s-SNOM), where tip acts as scattering probe. then total internal reflection (TIR)-based setup, both launching probing ultraconfined van der Waals materials (here phonon hexagonal boron nitride flakes), laying foundation s-SNOM-based interferometry Our results promise manifold applications, example, situ studies between molecular vibrations or chemical reactions at bare functionalized surfaces polaritonic materials.