Excitation of Josephson plasma waves in a layered high-temperature superconductor slab embedded in a high refractive index dielectric

The nonlocal optical response of a layered high-temperature superconductor slab embedded in a dielectric medium is theoretically studied. It is assumed that the layers inside the high-temperature superconductor are parallel to the slab surfaces. We calculate its p-polarization optical spectra by using an average permittivity tensor which depends on both the frequency and the wave vector of the electromagnetic wave. Consequently, additional electromagnetic modes just above the characteristic Josephson plasma frequency, being in the terahertz range, are generated. It is shown that the p-polarization reflectivity spectra for a Bi2Sr2CaCu2O8 + delta (Bi2212) superconductor slab, embedded in high refractive index dielectric, exhibit prominent dips breaking the total internal reflection. For very small superconductor slab thicknesses, the optical spectra resonances are associated with Fabry-Perot resonances of the short-wavelength electromagnetic modes. In contrast, the long-wavelength electromagnetic modes, having anomalous dispersion relation, are excited at relatively-large slab thicknesses and manifest themselves as strong resonances in both absorption and transmissivity spectra, suppressing the specular reflectivity.