Multiple Kerker anapoles in dielectric microspheres

TL;DR

This paper demonstrates how pure dipolar illumination can reveal dipolar scattering regimes, Kerker conditions, and hybrid anapoles in dielectric microspheres regardless of size, with experimental validation using focused Gaussian beams.

Contribution

It introduces a method to observe dipolar regimes and anapoles in dielectric spheres under dipolar illumination, independent of size and refractive index, and confirms experimental feasibility.

Findings

Kerker conditions relate to duality symmetry and asymmetric scattering.

Hybrid anapoles are identified as non-radiating sources.

Dipolar features are reproducible with focused Gaussian beams.

Abstract

High refractive index dielectric spheres present remarkable light-scattering properties in the spectral range dominated by dipolar modes. However, most of these properties are absent for larger spheres under plane wave illumination. Here, we propose to unravel dipolar regimes regardless of the sphere size and refractive index by illuminating with a pure dipolar field. This type of illumination ensures that the scattering response of the sphere is purely dipolar. In this scenario, we show that Kerker conditions are not only related to duality symmetry and a strong backward-to-forward asymmetric light-scattering, but also to the appearance of non-radiating sources: the so-called hybrid anapoles. Finally, we show that all the abovementioned scattering features under dipolar illumination are reproducible with an experimentally accessible tightly-focused Gaussian beam.