Near-field enhancement by waveguide-plasmon polaritons in a nonlocal metasurface

TL;DR

This paper demonstrates that coupling waveguide-plasmon polaritons with a nanoparticle lattice significantly enhances near-field intensity, enabling highly nonlocal metasurfaces for advanced optical applications.

Contribution

It introduces a novel approach of combining waveguide-plasmon polaritons with nanoparticle lattices to achieve unprecedented near-field enhancement in metasurfaces.

Findings

Near-field intensity increased by a factor of 80 over single-particle resonance.

Achieved 7-fold enhancement over traditional lattice-resonance.

The method enables highly nonlocal optical metasurfaces for various applications.

Abstract

Localized surface plasmons in metal nanoparticles are widely used in nano-optics to confine and enhance optical fields. It has been previously shown that, if the nanoparticles are distributed periodically, an additional enhancement can be achieved by coupling the localized surface plasmons to the diffraction orders of the lattice, forming surface lattice resonances. In this work, we study an even further improvement of the near-field enhancement by placing a metal-dielectric slab waveguide beneath the lattice of the particles to excite coupled waveguide-plasmon polaritons. These excitations can extend over many periods of the lattice, making the metasurface highly nonlocal. We numerically demonstrate that the approach can provide a significant extra increase in the near-field intensity -- by a factor of 80 over that produced by a single-particle plasmon resonance and by 7 over the lattice-resonance enhancement. The described enhancement mechanism can be used to design extraordinarily efficient nonlocal optical metasurfaces for many applications, including surface-enhanced Raman spectroscopy, fluorescence spectroscopy, nonlinear optics, and solar energy harvesting.