Phonon Polaritons in Calcite Microcubes

Phonon polaritons arise from phonon-photon coupling in ionic crystals. These hybrid phenomena enable sub-diffraction confinement of light with potential applications in nanophotonics such as wavefront manipulation, sensing, and infrared non-linear effects. Due to their metallic character at infrared wavelengths (i.e., negative permittivity), ionic crystals can excite phonon polariton modes within their Reststrahlen bands. Calcite (CaCO₃), a naturally hyperbolic material, exhibits hyperbolicity within its two Reststrahlen bands. In this work, we investigate phonon polaritons in calcite microcubes grown through ammonium carbonate diffusion. The grown microcubes are of the order of 10 µm in size. We determine the direction of the optical axis of the material using Raman Spectroscopy. We study the nature of the phonon polariton modes excited using experimental techniques including Fourier Transform infrared (FTIR) reflectivity, and Raman scattering mapping. We measured several phonon polariton modes from the calcite microcubes within the Reststrahlen bands with specific polarization selectivity given by the optical axes of the material.

This presentation would be ideally scheduled after the talk by E. Caudill entitled "Infrared Plasmon-Polariton Modes in Hyperbolic Metamaterials Made from III-V Semiconductor Multilayers"