Three-dimensional negative index of refraction at optical frequencies by coupling plasmonic waveguides

TL;DR

This paper proposes a novel method to achieve negative refraction at optical frequencies by coupling plasmonic waveguides, enabling the design of low-loss, isotropic metamaterials with negative index near 400 nm wavelength.

Contribution

It introduces a new approach using coupled plasmonic waveguides with modal symmetry control to realize negative index of refraction at optical frequencies.

Findings

Achieved negative index of -1 at 400 nm wavelength.

Demonstrated isotropic negative refraction using multilayer stacks.

Proposed design principles for low-loss optical metamaterials.

Abstract

We identify a route towards achieving a negative index of refraction at optical frequencies based on coupling between plasmonic waveguides that support backwards waves. We show how modal symmetry can be exploited in metal-dielectric waveguide pairs to achieve negative refraction of both phase and energy. By properly controlling coupling between adjacent waveguides, a metamaterial consisting of a one-dimensional multilayer stack exhibiting an isotropic index of -1 can be achieved at a free-space wavelength of 400 nm. The general concepts developed here may inspire new low-loss metamaterial designs operating close to the metal plasma frequency.