Optimum Forward Light Scattering by Spherical and Spheroidal Dielectric Nanoparticles with High Refractive Index

TL;DR

This paper demonstrates that spheroidal high-refractive index dielectric nanoparticles can achieve significantly higher forward light scattering than spherical ones by optimizing particle shape to overlap electric and magnetic dipole resonances, enabling efficient nanoantenna design.

Contribution

It introduces the concept that spheroidal particles can surpass spherical particles in forward scattering efficiency by shape optimization for resonance overlap.

Findings

Spheroidal particles achieve higher forward scattering than spherical particles.

Optimal particle shape minimizes backscattering while maximizing forward scattering.

Resonance overlap of electric and magnetic dipoles enhances scattering performance.

Abstract

High-refractive index dielectric nanoparticles may exhibit strong directional forward light scattering at visible and near-infrared wavelengths due to interference of simultaneously excited electric and magnetic dipole resonances. For a spherical high-index dielectric, the so-called first Kerker's condition can be realized, at which the backward scattering practically vanishes for some combination of refractive index and particle size. However, Kerker's condition for spherical particles is only possible at the tail of the scattering resonances, when the particle scatters light weakly. Here we demonstrate that significantly higher forward scattering can be realized if spheroidal particles are considered instead. For each value of refractive index exists an optimum shape of the particle, which produces minimum backscattering efficiency together with maximum forward scattering. This effect is achieved due to the overlapping of magnetic and electric dipole resonances of the spheroidal particle at the resonance frequency. It permits the design of very efficient, low-loss optical nanoantennas.