Nonlocal quasinormal modes for arbitrarily shaped three-dimensional plasmonic resonators

TL;DR

This paper develops a quasinormal mode framework to accurately describe nonlocal optical effects in arbitrarily shaped three-dimensional plasmonic nanoresonators, capturing shifts, damping, and spatial profiles beyond classical models.

Contribution

It introduces a novel quasinormal mode approach for nonlocal plasmonic resonators, enabling efficient analysis of their optical properties and quantum emitter interactions.

Findings

Accurately captures blueshift and damping in nonlocal plasmonic modes

Predicts modified spatial profiles of quasinormal modes

Calculates Purcell factors and spectra considering nonlocal effects

Abstract

Nonlocal effects have been shown to be responsible for a variety of non-trivial optical effects in small-size plasmonic nanoparticles, beyond classical electrodynamics. However, it is not clear whether optical mode descriptions can be applied to such extreme confinement regimes. Here, we present a powerful and intuitive quasinormal mode description of the nonlocal optical response for three-dimensional plasmonic nanoresonators. The nonlocal hydrodynamical model and a generalized nonlocal optical response model for plasmonic nanoresonators are used to construct an intuitive modal theory and to compare to the local Drude model response theory. Using the example of a gold nanorod, we show how an efficient quasinormal mode picture is able to accurately capture the blueshift of the resonances, the higher damping rates in plasmonic nanoresonators, and the modified spatial profile of the plasmon quasinormal modes, even at the single mode level. We exemplify the use of this theory by calculating the Purcell factors of single quantum emitters, the electron energy-loss spectroscopy spatial maps, as well as the Mollow triplet spectra of field-driven quantum dots with and without nonlocal effects for different size nanoresonators. Our nonlocal quasinormal mode theory offers a reliable and efficient technique to study both classical and quantum optical problems in nanoplasmonics.