Multimode directionality in all-dielectric metasurfaces

TL;DR

This paper demonstrates that all-dielectric nanostructures lacking rotational symmetry can support multiple magnetic dipole resonances, enabling multi-frequency unidirectional scattering and improving metasurface efficiency across telecom bands.

Contribution

It introduces the concept of multimode magnetic resonances in asymmetric dielectric nanostructures and verifies their effects experimentally, advancing metasurface design.

Findings

Multiple magnetic dipole resonances can be spectrally excited in asymmetric dielectric structures.

Constructive interference of magnetic and electric dipoles leads to multi-frequency unidirectional scattering.

Experimental microwave demonstrations confirm theoretical predictions.

Abstract

We demonstrate that spectrally diverse multiple magnetic dipole resonances can be excited in all-dielectric structures lacking rotational symmetry, in contrast to conventionally used spheres, disks or spheroids. Such multiple magnetic resonances arise from hybrid Mie-Fabry-P\'{e}rot modes, and can constructively interfere with induced electric dipole moments, thereby leading to novel multi-frequency unidirectional scattering. Here we focus on elongated dielectric nanobars, whose magnetic resonances can be spectrally tuned by their aspect ratios. Based on our theoretical results, we suggest all-dielectric multimode metasurfaces and verify them in proof-of-principle microwave experiments. We also believe that the demonstrated property of multimode directionality is largely responsible for the best efficiency of all-dielectric metasurfaces that were recently shown to operate across multiple telecom bands.