Probing the Ultimate Limits of Plasmonic Enhancement

TLDR

Metals support surface plasmons that localize light to subwavelength regions, and the resulting field enhancements set ultimate limits for nonlinear and quantum optical phenomena. A semiclassical model of the electronic response of a metal imposes strict bounds on ultimate field enhancement, validated by optical scattering experiments on gold nanoparticles positioned a few angstroms from a gold film. The dominant limiting factor is the intrinsic nonlocality of the metal’s dielectric response, and the derived bounds constrain all nanophotonic systems.

Abstract

Metals support surface plasmons at optical wavelengths and have the ability to localize light to subwavelength regions. The field enhancements that occur in these regions set the ultimate limitations on a wide range of nonlinear and quantum optical phenomena. We found that the dominant limiting factor is not the resistive loss of the metal, but rather the intrinsic nonlocality of its dielectric response. A semiclassical model of the electronic response of a metal places strict bounds on the ultimate field enhancement. To demonstrate the accuracy of this model, we studied optical scattering from gold nanoparticles spaced a few angstroms from a gold film. The bounds derived from the models and experiments impose limitations on all nanophotonic systems.