Theory of fishnet negative-index optical metamaterials

TL;DR

This paper develops a microscopic, semi-analytical model to understand fishnet negative-index optical metamaterials, revealing how surface plasmon coupling leads to negative refraction and extending the theory to include gain media for loss compensation.

Contribution

It introduces a detailed microscopic description and a semi-analytical model for fishnet metamaterials at optical frequencies, advancing understanding of their negative-index behavior.

Findings

Accurate formulas for real and imaginary parts of the refractive index.

Explanation of surface plasmon coupling at waveguide intersections.

Extension of the theory to loss-compensated metamaterials with gain.

Abstract

We theoretically study fishnet metamaterials at optical frequencies. In contrast to earlier works, we provide a microscopic description by tracking the transversal and longitudinal flows of energy through the fishnet mesh composed of intersecting subwavelength plasmonic waveguides. The analysis is supported by a semi-analytical model based on surface-plasmon coupled-mode equations, which provides accurate formulas for the fishnet refractive index, including the real-negative and imaginary parts. The model simply explains how the surface plasmons couple at the waveguide intersections and it shines new light on the fishnet negative-index paradigm at optical frequencies. Extension of the theory for loss-compensated metamaterials with gain media is also presented.