Excitation of plasmonic waveguide modes using principles of holography

Abstract

A method for development of gratings for effective excitation of surface plasmonic waves using holography principles has been proposed and theoretically analyzed. The case of excitation of a plasmonic wave in a dielectric layer on metal using volume holograms in the dielectric layer has been considered. For comparison, simple periodic gratings with refractive index of the dielectric layer modulated in the plane of the layer and invariable in the direction perpendicular to the layer plane have been considered. The efficiencies of the proposed holograms and gratings optimized for various incidence angles of exciting waves incident on the gratings/holograms from air have been analyzed. Based on this analysis, general enough conditions when holograms can be more efficient than simple gratings have been found out. In particular, a hologram is expected to be more efficient than the grating when the refractive index distribution in the hologram is considerably inhomogeneous (contrary to the gratings) in the direction perpendicular to the layer plane. For example, this may be the case if the exciting wave is incident on a hologram obliquely at a rather large angle or if phase fronts of either exciting wave or a wave being excited are curved. The proposed holographic method is quite universal. As expected, this can be extended for efficient excitation of different types of optical surface waves and modes of optical waveguides.