Directional surface plasmon polariton scattering by single low-index dielectric nanoparticles: simulation and experiment

Abstract

Directionally scattered surface plasmon polaritons (SPPs) promote the efficiency of plasmonic devices by limiting the energy within a given spatial domain, which is one of the key issues to plasmonic devices. Benefitting from the magnetic response induced in high-index dielectric nanoparticles, unidirectionally scattered SPPs have been achieved via interference between electric and magnetic resonances excited in the particles. Yet, as the magnetic response in low-index dielectric nanoparticles is too weak, the directionally scattered SPPs are hard to detect. In this work, we demonstrate forward scattered SPPs in single low-index polystyrene (PS) nanospheres. We numerically illustrate the excitation mechanism of plasmonic induced electric and magnetic multipole modes, as well as their contributions to forward SPP scattering of single PS nanospheres. We also simulate the SPP scattering field distribution obtaining a forward-to-backward scattering intensity ratio of 50.26:1 with 1 μm PS particle. Then the forward scattered SPPs are experimentally visualized by Fourier transforming the real-space plasmonic imaging to k-space imaging. The forward scattered SPPs from low-index dielectric nanoparticles pave the way for SPP direction manipulation by all types of nanomaterials.