Selective excitation of plasmons superlocalized at sharp perturbations of metal nanoparticles

Abstract

Sharp metal corners and tips support plasmons localized on the scale of the curvature radiussuperlocalized 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.

Key Parameter Controlling the Sensitivity of Plasmonic Metal Nanoparticles: Aspect Ratio

“…With respect to plasmonic sensitivity to refractive index changes surrounding the whole nanoparticle, however, the effect of sharp features diminishes and polarizability of the whole nanoparticles plays a significant role, based on the quasistatic localized plasmon resonance theory . As also suggested in the theoretical work by Gorkunov et al, the plamons at the sharp tips and edges do not necessarily provide a significant contribution to the particle polarizatbility. Instead, the polarizability is mainly controlled by the plasmons determined by the whole particle or, more specifically, the nanoparticle aspect ratio (vide infra).…”

Extended UV detection bandwidth: h-BN/Al powder nanocomposites photodetectors sensitive in a middle UV region due to localized surface plasmon resonance effect

“…Besides, plasmons can be localized by tip-shaped surface perturbations of metallic nanoparticles, and in this case they are called superlocalized plasmons [41]. Nanoparticles of Au, Pt, and Ag are widely studied as the plasmonic nanoantennas because of strong SPR effect in these metals.…”