Resonant reflectance dips induced by coupled surface plasmon polaritons in thin metal-film/dielectric superlattices

The optical reflectance of metal films changes dramatically as the film thickness becomes thinner than the electron mean free path. We have developed a transfermatrix formalism for deducing the dispersion relations of the electromagnetic waves in infinite and semi-infinite metal-dielectric superlattices by taking into account the presence of the size effect and coupled plasmon waves. This work shows that the resonance frequency occurring at the reflecting dip increases while the bandwidth decreases as the thickness of the dielectric films increases. Reducing the values of p and q shifts the resonance frequency upward and yields multiple numbers of minimum reflectivity.