The field of plasmonics investigates how electromagnetic fields can be confined into sub- wavelength dimensions. This discipline constitutes a major subset of nano-photonics, and is enabled by the rich physics of light-matter interactions at the nano-scale. However, at the lower end of the length scales involved in plasmonic devices, metals are often shaped to have dimensions that approach the thickness of only a few atomic layers, which makes classical local electrodynamics insufficient due to the emergence of nonlocal and quantum effects that are not included in the model.
In this thesis we focus specifically on nonlocal effects, investigating their impact in exper- imentally relevant plasmonic nanostructures. In order to describe the spatial dispersion in the metal permittivity, we develop a full three-dimensional nonlocal hydrodynamic solution of Maxwell’s equations in frequency domain, complementing it with analytical closed form solutions where possible.
In this way, effects of nonlocal electron-electron interactions in the dielectric response of metals are taken into account in a phenomenological fashion, offering deep insights into the way spatial dispersion modifies the electromagnetic response of plasmonic nano- structures.
The geometries we investigate are driven by both plane wave and electron beam sources, mimicking experimental conditions. We use our numerical approach to perform an exhaustive analysis of the impact of nonlocality in the plasmonic response of five ex- perimentally relevant plasmonic structures: plasmonic hourglass metal-insulator-metal waveguides, kissing metallic nanowires, nanofocusing metallic tips, three-dimensional nanocrescent light harvesters, and coupled metallic nanoprisms under electron beam excitation.
Our results demonstrate the complexity of the interplay between nonlocal and geometric effects taking place in the structures under investigation. We discuss the different sens- itivities to both effects of the various plasmonic modes supported by these structures.