Dielectric theory of interacting excitonic resonances

Abstract

The dielectric function is developed for two interacting excitonic resonances with spatial dispersion. The longitudinal-transverse energy splitting and the reflectivity of these resonances depend very strongly on the energy separation between the resonances. It is shown that simple interpretations of reflection spectra of degenerate resonances split by external fields may yield incorrect oscillator strengths or polarizabilities and resonance frequency shifts. The energy versus wave-vector polariton dispersion relation is obtained and plotted for the materials CdS and ZnO as examples. Effective refractive indices are derived to be used in the generalized multilayer Fresnel formula for oblique incidence of light polarized parallel and perpendicular to the plane of incidence.