Effective surface conductivity of plasmonic metasurfaces: from far-field characterization to surface wave analysis

TL;DR

This paper demonstrates that an effective surface conductivity tensor can accurately describe the optical properties of anisotropic plasmonic metasurfaces in both near- and far-field regimes, enabling better surface wave analysis and design.

Contribution

It introduces a method to extract and validate an effective surface conductivity tensor from experimental and numerical data for anisotropic metasurfaces.

Findings

Effective surface conductivity tensor accurately describes metasurface optical properties.

Predicted existence of TE- and TM-polarized surface plasmons across a wide frequency range.

Identified topological transition from elliptical to hyperbolic plasmon dispersion.

Abstract

Metasurfaces offer great potential to control near- and far-fields through engineering of optical properties of elementary cells or meta-atoms. Such perspective opens a route to efficient manipulation of the optical signals both at nanoscale and in photonics applications. In this paper we show that by using an effective surface conductivity tensor it is possible to unambigiously describe optical properties of an anisotropic metasurface in the far- and near-field regimes. We begin with retrieving the effective surface conductivity tensor from the comparative analysis of experimental and numerical reflectance spectra of a metasurface composed of elliptical gold nanoparticles. Afterwards restored conductivities are validated in the crosscheck versus semianalytic parameters obtained with the discrete dipole model with and without dipoles interaction contribution. The obtained effective parameters are further used for the dispersion analysis of surface plasmons localized at the metasurface. The effective medium model predicts existence of both TE- and TM-polarized plasmons in a wide range of optical frequencies and describes peculiarities of their dispersion, in particularly, topological transition from the elliptical to hyperbolic regime with eligible accuracy. The analysis in question offers a simple practical way to describe properties of metasurfaces including ones in the near-field zone by extracting effective parameters from the convenient far-field characterisation.