Experimental and numerical studies of near-field infrared phenomena at nanometer length scales

Broadband near-field infrared spectroscopy is fast emerging as a valuable experimental probe of nanomaterials. Light-matter interactions in polaritonic materials at nanometer length scales can be probed effectively with this experimental technique. When there is strong coupling of light to the probe-sample system in highly polar materials such as insulating SrTiO₃, the phonon-polariton resonances should be described by detailed numerical simulations. More generally, experimental data needs to be accurately modeled to obtain optical properties at nanometer length scales in non-trivial geometries such as multilayered samples (for example, insulating SrTiO₃ crystal with metallic surface), and materials with physical boundaries comparable to the probe apex (for example, nano-platelets of Cu₂S). Near-field infrared spectra of materials with anisotropic dielectric function can also be modeled numerically (for example, rutile TiO₂). We will present our results on the materials described above, thereby establishing the efficacy of detailed numerical simulations for analyzing experimental spectra.