Long-range surface plasmons in dielectric-metal-dielectric structure with highly anisotropic substrates

Abstract

We present a theoretical study of long-range surface plasmons propagating in a thin metallic film clad between two identical uniaxial anisotropic dielectric crystals. We show that the proper orientation of the optical axis of the crystal with respect to the metal surface enhances the propagation length of surface plasmons. Since the proper orientation depends on surface plasmon frequency, we give the results for the propagation length in a wide range of frequencies, including the telecommunication region. To increase the role of anisotropy, we consider artificial substrates from photonic crystals, which possess an order of magnitude stronger anisotropy than the natural optical crystals. We propose Kronig-Penney model for plasmonic crystal where the substrate is a periodic sequence of dielectric delta peaks. In this model the dispersion relation for surface plasmon has a band structure where the band width tends to zero when the frequency approaches the resonant frequency.