Planar Chirality of Plasmonic Multi-Split Rings

TL;DR

This paper presents an analytical framework for planar chiral multi-split rings, revealing how their geometry and impedance loads influence magneto-electric coupling and enabling detection of chirality through optical measurements.

Contribution

It introduces a novel Fourier series-based model for analyzing planar chiral rings with arbitrary splits and loads, advancing understanding of their electromagnetic properties.

Findings

Planar chirality causes magneto-electric coupling in split rings.

Impedance loads can generate dissymmetric current distributions.

Chirality can be detected via reflection and transmission measurements.

Abstract

We develop an analytical framework for the analysis of planar chiral multi-split rings, based on a Fourier series expansion of the induced current. The number, width, and location of each split (gap) is arbitrary. Provision is made for the possibility of inserting lumped active or passive impedance loads in the gaps. The model demonstrates the hallmark of planar chirality and its consequent magneto-electric coupling as a function of the parameters of the splits and impedance loads. It is demonstrated that impedance loads sequenced in a clockwise or anti-clockwise fashion allow for generation of dissymetric current distributions in the plane, like for geometric (structural) chirality. We also determine the effect of planar chirality on the relevant dyadic polarizability components of a split ring. Reflection and transmission coefficient characteristics of regular arrays of such rings are determined with the aid of the periodic method of moments. Phase-coherent detection of the sense of handedness and incoherent detection of planar chirality per se by measurement of the field intensity are shown to be possible, in both the reflection and transmission characteristics. These results are relevant to both coherent and incoherent detection at optical and suboptical wavelengths.