Constructive and Destructive Interference of Kerker-type Scattering in an Ultra-thin Silicon Huygens Metasurface

TL;DR

This paper demonstrates how interference of multipole modes in a silicon nanodisk metasurface can be engineered to achieve suppressed backward scattering, advancing Huygens source design and metasurface applications.

Contribution

It introduces a novel Kerker-type scattering mechanism involving electric, toroidal, and magnetic quadrupole modes in ultra-thin silicon metasurfaces, verified through experiments and modeling.

Findings

Constructive interference between electric and toroidal dipoles.

Destructive interference between electric dipole and magnetic quadrupole causes suppressed backward scattering.

Model accurately predicts reflection dips and interference effects.

Abstract

High refractive index dielectric nanoparticles have provided a new platform for exotic light manipulation through the interference of multipole modes. The Kerker effect is one example of a Huygens source design. Rather than exploiting interference between the electric dipole and magnetic dipole, as in many conventional Huygens source designs, we explore Kerker-type suppressed backward scattering mediated by the dominant electric dipole, toroidal dipole and magnetic quadrupole. These modes are provided by a designed and fabricated CMOS compatible ultra-thin Silicon nanodisk metasurface with a suppressed magnetic dipole contribution, and verified through multipole decomposition. The non-trivial substrate effect is considered using a semi-analytical transfer matrix model. The model successfully predicts the observed reflection dip. By applying a general criterion for constructive and destructive interference, it is shown that while constructive interference occurs between the electric and toroidal dipole contributions, the experimentally observed suppressed backward Kerker-type scattering arises from the destructive interference between backward scattered contributions due to the total electric dipole and the magnetic quadrupole. Our study paves the way towards new types of Huygens sources or metasurface design, such as for peculiar transverse Kerker scattering.