The conditions for the preservation of duality symmetry in a linear medium

TL;DR

This paper investigates the specific conditions under which electromagnetic duality symmetry can be preserved in linear media, extending the concept of optical helicity and exploring the properties and feasibility of duality symmetric materials.

Contribution

It generalizes the definition of optical helicity to linear media and discusses the conditions and properties of media that can preserve duality symmetry.

Findings

Conditions for duality symmetry preservation identified

Generalized optical helicity in linear media formulated

Decoupling of opposite helicities shown in duality symmetric media

Abstract

Electric magnetic duality symmetry is well understood in vacuum. For light propagating through a medium this symmetry is typically broken. We investigate under what conditions duality transformation is preserved in a linear medium and employ these conditions to generalise the definition of optical helicity to a general linear medium. We will discuss some unique properties duality symmetric media possess, provided they exist and reformulate Maxwell's equation in such a way that they explicitly show the decoupling of opposite helicities. The feasibility of constructing a duality symmetric medium is discussed.