All-dielectric reciprocal bianisotropic nanoparticles

TL;DR

This paper introduces a new class of all-dielectric nanoparticles with tunable magneto-electric coupling due to broken symmetry, enabling advanced control of light reflection and scattering without metallic components.

Contribution

It demonstrates that symmetry-breaking in dielectric nanoparticles induces bianisotropy, allowing for customizable optical properties and phase control in reflectarray applications.

Findings

Breaking symmetry induces magneto-electric coupling.

Nanoparticles achieve a 2π phase shift with high reflection amplitude.

Array design enables near-perfect transmission outside resonance.

Abstract

The study of high-index dielectric nanoparticles currently attracts a lot of attention. They do not suffer from absorption but promise to provide control on the properties of light comparable to plasmonic nanoparticles. To further advance the field, it is important to identify versatile dielectric nanoparticles with unconventional properties. Here, we show that breaking the symmetry of an all-dielectric nanoparticle leads to a geometrically tunable magneto-electric coupling, i.e. an omega-type bianisotropy. The suggested nanoparticle exhibits different backscatterings and, as an interesting consequence, different optical scattering forces for opposite illumination directions. An array of such nanoparticles provides different reflection phases when illuminated from opposite directions. With a proper geometrical tuning, this bianisotropic nanoparticle is capable of providing a $2\pi$ phase change in the reflection spectrum while possessing a rather large and constant amplitude. This allows creating reflectarrays with near-perfect transmission out of the resonance band due to the absence of an usually employed metallic screen.