Quasi-Homogeneous Backward-Wave Plasmonic Structures: Theory and Accurate Simulation

TL;DR

This paper demonstrates the existence of backward waves and negative refraction in quasi-homogeneous plasmonic crystals with very small lattice cells, using an advanced finite-difference method for accurate simulation.

Contribution

It introduces the application of FLAME, a novel finite-difference technique, for precise computation of Bloch bands in plasmonic structures exhibiting backward waves.

Findings

Backward waves exist in plasmonic crystals with sub-wavelength lattice cells.

FLAME provides highly accurate solutions by incorporating local analytical approximations.

The method simplifies eigenproblem solving by producing linear equations.

Abstract

Backward waves and negative refraction are shown to exist in plasmonic crystals whose lattice cell size is a very small fraction of the vacuum wavelength (less than 1/40th in an illustrative example). Such ``quasi-homogeneity'' is important, in particular, for high-resolution imaging. Real and complex Bloch bands are computed using the recently developed finite-difference calculus of ``Flexible Local Approximation MEthods'' (FLAME) that produces linear eigenproblems, as opposed to quadratic or nonlinear ones typical for other techniques. FLAME dramatically improves the accuracy by incorporating local analytical approximations of the solution into the numerical scheme.