Plasmonic interaction between nanospheres

TL;DR

This paper introduces new analytical and numerical methods to accurately model the electromagnetic interactions between nearly touching plasmonic nanospheres, overcoming computational challenges and limitations of classical approaches.

Contribution

It develops fully analytic solutions for two plasmonic spheres and a hybrid numerical scheme for multiple spheres, enhancing efficiency and accuracy in near-touching conditions.

Findings

Analytic solutions for two plasmonic spheres derived.

Hybrid numerical scheme effective for multiple spheres.

Methods are accurate even when spheres are nearly touching.

Abstract

When metallic (or plasmonic) nanospheres are nearly touching, strong concentration of light can occur in the narrow gap regions. This phenomenon has a potential application in nanophotonics, biosensing and spectroscopy. The understanding of the strong interaction between the plasmonic spheres turns out to be quite challenging. Indeed, an extremely high computational cost is required to compute the electromagnetic field. Also, the classical method of image charges, which is effective for dielectric spheres system, is not valid for plasmonic spheres because of their negative permittivities. Here we develop new analytical and numerical methods for the plasmonic spheres system by clarifying the connection between transformation optics and the method of image charges. We derive fully analytic solutions valid for two plasmonic spheres. We then develop a hybrid numerical scheme for computing the field distribution produced by an arbitrary number of spheres. Our method is highly efficient and accurate even in the nearly touching case and is valid for plasmonic spheres.