Optical Chirality of Time-Harmonic Wavefields for Classification of Scatterers

TL;DR

This paper develops a theoretical framework to classify scatterers based on their electromagnetic chirality response, introducing concepts like duality and helicity, and validates these with model examples and experimental comparisons.

Contribution

It introduces a comprehensive method to classify scatterers by their chiral electromagnetic responses using T-matrix analysis and new symmetry concepts.

Findings

Classification of scatterers based on chirality and duality.

Analysis of spherical and non-spherical particles with high refractive index.

Comparison with experimental data confirms theoretical predictions.

Abstract

We derive expressions for the scattering, extinction and conversion of the chirality of monochromatic light scattered by bodies which are characterized by a T-matrix. In analogy to the conditions obtained from the conservation of energy, these quantities enable the classification of arbitrary scattering objects due to their full, i.e. either chiral or achiral, electromagnetic response. To this end, we put forward and determine the concepts of duality and breaking of duality symmetry, anti-duality, helicity variation, helicity annhiliation and the breaking of helicity annihilation. Different classes, such as chiral and dual scatterers, are illustrated in this analysis with model examples of spherical and non-spherical shape. As for spheres, these concepts are analysed by considering non-Rayleigh dipolar dielectric particles of high refractive index, which, having a strong magnetic response to the incident wavefield, offer an excellent laboratory to test and interpret such changes in the chirality of the illumination. In addition, comparisons with existing experimental data are made.