Invisible nanowires with interfering electric and toroidal dipoles

TL;DR

This paper investigates how toroidal dipoles contribute to nanowire scattering and demonstrates that destructive interference between electric and toroidal dipoles can render nanowires invisible, with implications for non-invasive sensing.

Contribution

It reveals the role of toroidal dipoles in nanowire scattering and proposes a method to achieve invisibility through dipole interference in dielectric nanowires.

Findings

Toroidal dipoles can be excited in dielectric nanowires in the optical spectrum.

Destructive interference of electric and toroidal dipoles can render nanowires invisible.

Potential applications in non-invasive biological and medical sensing.

Abstract

By studying the scattering of normally incident planewaves by a single nanowire, we reveal the indispensable role of toroidal multipole excitation in multipole expansions of radiating sources. It is found that for both p-polarized and s-polarized incident waves, toroidal dipoles can be effectively excited within homogenous dielectric nanowires in the optical spectrum regime. We further demonstrate that the plasmonic core-shell nanowires can be rendered invisible through destructive interference of the electric and toroidal dipoles, which may inspire many nanowire based light-matter interaction studies, and incubate biological and medical applications that require non-invasive detections and measurements.