# Influence of spatial dispersion on surface plasmons, nanoparticles and grating couplers

## TL;DR

This paper demonstrates that spatial dispersion significantly influences surface plasmons, nanoparticles, and grating couplers, especially in high permittivity dielectrics, highlighting the need to consider nonlocal effects in plasmonic modeling.

## Contribution

It shows that nonlocality affects surface plasmons and nanoparticle responses, emphasizing the importance of using advanced models like the hydrodynamic model in high permittivity environments.

## Key findings

- Spatial dispersion impacts surface plasmon propagation.
- Nanoparticles larger than 20 nm are sensitive to spatial dispersion.
- High permittivity dielectrics require nonlocality considerations in plasmonic structures.

## Abstract

Recent experiments have shown that spatial dispersion may have a conspicuous impact on the response of plasmonic structures. This suggests that in some cases the Drude model should be replaced by more advanced descriptions that take spatial dispersion into account, like the hydrodynamic model. Here we show that nonlocality in the metallic response affects surface plasmons propagating at the interface between a metal and a dielectric with high permittivity. As a direct consequence, any nanoparticle with a radius larger than 20 nm can be expected to be sensitive to spatial dispersion whatever its size. The same behavior is expected for a simple metallic grating allowing the excitation of surface plasmons, just as in Wood's famous experiments. Importantly, our work suggests that for any plasmonic structure in a high permittivity dielectric, nonlocality should be taken into account.