Selective excitation of plasmons superlocalized at sharp perturbations of metal nanoparticles

TL;DR

This paper investigates how sharp features on metal nanoparticles can support superlocalized plasmons, enabling highly selective and intense local light enhancement useful for nano-antenna applications.

Contribution

It introduces a hybridization model of superlocalized and ordinary plasmons on nanoparticles with sharp perturbations, revealing mechanisms for selective excitation and hot-spot formation.

Findings

Superlocalized plasmons are supported at sharp corners and tips.

Hybridization between superlocalized and ordinary plasmons enhances local fields.

Nanoparticles can act as nano-antennas with highly localized light enhancement.

Abstract

Sharp metal corners and tips support plasmons localized on the scale of the curvature radius -- superlocalized plasmons. We analyze plasmonic properties of nanoparticles with small and sharp corner- and tip-shaped surface perturbations in terms of hybridization of the superlocalized plasmons, which frequencies are determined by the perturbations shape, and the ordinary plasmons localized on the whole particle. When the frequency of a superlocalized plasmon gets close to that of the ordinary plasmon, their strong hybridization occurs and facilitates excitation of an optical hot-spot near the corresponding perturbation apex. The particle is then employed as a nano-antenna that selectively couples the free-space light to the nanoscale vicinity of the apex providing precise local light enhancement by several orders of magnitude.