Off-resonance field enhancement by spherical nanoshells

TL;DR

This paper investigates how spherical nanoshells made of metal and dielectric materials can enhance local electromagnetic fields outside of resonance conditions, with potential applications in nonlinear photonics.

Contribution

It introduces the concept of off-resonance field enhancement in spherical nanoshells and links it to Fano resonances, expanding understanding of nanoscale light-matter interactions.

Findings

Field enhancement occurs outside resonance regions ('dark states').

Optimal conditions lead to stronger internal dielectric field enhancement.

Potential for nonlinear photonics applications using nonlinear dielectric materials.

Abstract

We study light scattering by spherical nanoshells consistent of metal/dielectric composites. We consider two geometries of metallic nanoshell with dielectric core, and dielectric coated metallic nanoparticle. We demonstrate that for both geometries the local field enhancement takes place out of resonance regions ("dark states"), which, nevertheless, can be understood in terms of the Fano resonance. At optimal conditions the light is stronger enhanced inside the dielectric material. By using nonlinear dielectric materials it will lead to a variety nonlinear phenomena applicable for photonics applications.