Excitation of surface plasmon-polaritons in metal films with double periodic modulation: anomalous optical effects

TL;DR

This paper presents a comprehensive theoretical analysis of resonance effects in double periodically modulated metal films, explaining anomalous optical phenomena like enhanced light transmittance and their relation to surface plasmon-polaritons.

Contribution

It generalizes existing one-dimensional theories to two-dimensional structures and applies the results to films with cylindrical inclusions, connecting theory with experimental observations.

Findings

Identification of multiple resonance phenomena in modulated films

Analysis of transformation coefficients near resonances

Comparison with experiments showing enhanced light transmittance

Abstract

We perform a thorough theoretical analysis of resonance effects when an arbitrarily polarized plane monochromatic wave is incident onto a double periodically modulated metal film sandwiched by two different transparent media. The proposed theory offers a generalization of the theory that had been build in our recent papers for the simplest case of one-dimensional structures to two-dimensional ones. A special emphasis is placed on the films with the modulation caused by cylindrical inclusions, hence, the results obtained are applicable to the films used in the experiments. We discuss a spectral composition of modulated films and highlight the principal role of ``resonance'' and ``coupling'' modulation harmonics. All the originating multiple resonances are examined in detail. The transformation coefficients corresponding to different diffraction orders are investigated in the vicinity of each resonance. We make a comparison between our theory and recent experiments concerning enhanced light transmittance and show the ways of increasing the efficiency of these phenomena. In the appendix we demonstrate a close analogy between ELT effect and peculiarities of a forced motion of two coupled classical oscillators.