Toroidal optical activity

TL;DR

This paper demonstrates a novel form of optical activity caused by toroidal dipole moments, which cannot be explained by traditional electric and magnetic multipoles, expanding understanding of light-matter interactions.

Contribution

It provides experimental and numerical evidence for optical activity driven by toroidal dipoles, a previously overlooked multipole contribution.

Findings

Optical activity observed cannot be explained by electric/magnetic multipoles.

Toroidal dipole moments are essential to account for the observed optical activity.

Experimental results confirm the role of toroidal multipoles in optical phenomena.

Abstract

Optical activity is ubiquitous across natural and artificial media and is conventionally understood in terms of scattering from electric and magnetic moments. Here we demonstrate experimentally and confirm numerically a type of optical activity that cannot be attributed to electric and magnetic multipoles. We show that our observations can only be accounted for by the inclusion of the toroidal dipole moment, the first term of the recently established peculiar family of toroidal multipoles.