A microscopic view of the electromagnetic properties of sub-wavelength metallic surfaces

TL;DR

This paper provides a detailed microscopic analysis of surface waves, specifically surface plasmon polaritons and quasi-cylindrical waves, on metallic surfaces with sub-wavelength indentations, elucidating their properties and interactions.

Contribution

It introduces a closed-form expression for quasi-CWs and presents a microscopic model explaining energy exchange between SPPs and quasi-CWs.

Findings

Identification of two distinct surface waves involved.

Derivation of a closed-form expression for quasi-CW.

Microscopic model explaining wave energy exchange.

Abstract

We review the properties of the surface waves that are scattered by two-dimensional sub-wavelength indentations on metallic surfaces. We show that two distinct waves are involved, a surface plasmon polariton (SPP) and a quasi-cylindrical wave (quasi-CW). We discuss the main characteristics of these waves, their damping characteristic lengths and their relative excitation weights as a function of the separation distance from the indentation and as a function of the metal conductivity. In particular we show that derive a closed-form expression for the quasi-CW, which clarifies its physical origin and its main properties. We further present an intuitive microscopic model, which explains how the elementary SPPs and quasi-CWs exchange their energies by multiple-scattering to build up a rich variety of near- and far-field optical effects.