Tailoring dielectric resonator geometries for directional scattering and Huygens' metasurfaces

TL;DR

This paper presents a methodology for designing dielectric resonators with tailored geometries to achieve directional scattering and Huygens' metasurfaces, by overlapping electric and magnetic dipole resonances using multipolar analysis and perturbation theory.

Contribution

The authors introduce a systematic approach to modify dielectric resonator geometries for controlled resonance overlap, enabling low-loss, scalable metasurface applications across various frequency bands.

Findings

Resonator geometry modifications enable resonance overlap.

Directional scattering achieved via first Kerker condition.

Resonance tuning applicable across microwave to infrared frequencies.

Abstract

In this paper we describe a methodology for tailoring the design of metamaterial dielectric resonators, which represent a promising path toward low-loss metamaterials at optical frequencies. We first describe a procedure to decompose the far field scattered by subwavelength resonators in terms of multipolar field components, providing explicit expressions for the multipolar far fields. We apply this formulation to confirm that an isolated high-permittivity cube resonator possesses frequency separated electric and magnetic dipole resonances, as well as a magnetic quadrupole resonance in close proximity to the electric dipole resonance. We then introduce multiple dielectric gaps to the resonator geometry in a manner suggested by perturbation theory, and demonstrate the ability to overlap the electric and magnetic dipole resonances, thereby enabling directional scattering by satisfying the first Kerker condition. We further demonstrate the ability to push the quadrupole resonance away from the degenerate dipole resonances to achieve local behavior. These properties are confirmed through the multipolar expansion and show that the use of geometries suggested by perturbation theory is a viable route to achieve purely dipole resonances for metamaterial applications such as wave-front manipulation with Huygens' metasurfaces. Our results are fully scalable across any frequency bands where high-permittivity dielectric materials are available, including microwave, THz, and infrared frequencies.