Measuring the electromagnetic chirality of 2D arrays under normal illumination

TL;DR

This paper introduces a quantitative electromagnetic chirality measure for 2D arrays under normal illumination, enabling comparison and analysis of array designs based on their complex reflection and transmission coefficients.

Contribution

The paper proposes a new electromagnetic chirality measure for 2D arrays that relies solely on reflection and transmission coefficients, facilitating design evaluation and comparison.

Findings

Helical arrays exhibit high electromagnetic chirality.

Substrate effects are less effective in breaking mirror symmetry.

The measure is bounded and useful for near- and far-field applications.

Abstract

We present an electromagnetic chirality measure for 2D arrays of subwavelength periodicities under normal illumination. The calculation of the measure uses only the complex reflection and transmission coefficients from the array. The measure allows the ordering of arrays according to their electromagnetic chirality, which further allows a quantitative comparison of different design strategies. The measure is upper bounded, and the extreme properties of objects with high values of electromagnetic chirality make them useful in both near- and far-field applications. We analyze the consequences that different possible symmetries of the array have on its electromagnetic chirality. We use the measure to study four different arrays. The results indicate the suitability of helices for building arrays of high electromagnetic chirality, and the low effectiveness of a substrate for breaking the transverse mirror symmetry.