Core-shell particles as building blocks for systems with high duality symmetry

TL;DR

This paper demonstrates how core-shell dielectric spheres can be engineered to significantly enhance electromagnetic duality symmetry, serving as effective building blocks for advanced metamaterials with high duality properties.

Contribution

It introduces a novel design of core-shell dielectric particles that achieve over an order of magnitude better duality symmetry than previous non-magnetic objects.

Findings

Core-shell particles exhibit significantly improved duality symmetry.

Using these particles as building blocks enhances the duality of composite systems.

The approach enables better approximation of intrinsically dual materials.

Abstract

Material electromagnetic duality symmetry requires a system to have equal electric and magnetic responses. Electromagnetic duality enables technologically important effects like artificial optical activity and zero back-scattering, is a requirement for metamaterials in transformation optics, Huygens wave-front control, and maximal electromagnetic chirality, and appears in topological photonic systems. Intrinsically dual materials that meet the duality conditions at the level of the constitutive relations do not exist in many frequency bands. Nevertheless, discrete objects like metallic helices and homogeneous dielectric spheres can be engineered to approximate the dual behavior. The discrete objects can then be used as building blocks with the objective of obtaining composite systems with high duality symmetry. Here, we exploit the extra degrees of freedom of a core-shell dielectric sphere to obtain a particle whose duality symmetry is more than one order of magnitude better than previously reported non-magnetic objects. We show that the improvement is transferred onto the duality symmetry of composite objects when the core-shell particle is used as a building block instead of homogeneous spheres.