Homogenization of resonant chiral metamaterials

TL;DR

This paper investigates the conditions under which chiral metamaterials can be effectively homogenized, revealing that strong coupling or excessive dilution can hinder homogenization, and provides analytical tools to predict these limits.

Contribution

It introduces an analytical criterion and a predictive tool for homogenization limits in chiral metamaterials, considering the effects of meta-atom density and coupling strength.

Findings

A critical density exists for homogenization of chiral metamaterials.

Strong coupling can prevent homogenization entirely.

Excessive dilution leads to photonic crystal-like features.

Abstract

Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as e.g. propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size a critical density exists above which increasing coupling between neighboring meta-atoms prevails a reasonable homogenization. On the contrary, a dilution in excess will induce features reminiscent to photonic crystals likewise prevailing a homogenization. Based on Bloch mode dispersion we introduce an analytical criterion for performing the homogenization and a tool to predict the homogenization limit. We show that strong coupling between meta-atoms of chiral metamaterials may prevent their homogenization at all.