Nonlocal quasinormal modes for arbitrarily shaped three-dimensional plasmonic resonators

Abstract

Nonlocal effects have been shown to be responsible for a variety of\nnon-trivial optical effects in small-size plasmonic nanoparticles, beyond\nclassical electrodynamics. However, it is not clear whether optical mode\ndescriptions can be applied to such extreme confinement regimes. Here, we\npresent a powerful and intuitive quasinormal mode description of the nonlocal\noptical response for three-dimensional plasmonic nanoresonators. The nonlocal\nhydrodynamical model and a generalized nonlocal optical response model for\nplasmonic nanoresonators are used to construct an intuitive modal theory and to\ncompare to the local Drude model response theory. Using the example of a gold\nnanorod, we show how an efficient quasinormal mode picture is able to\naccurately capture the blueshift of the resonances, the higher damping rates in\nplasmonic nanoresonators, and the modified spatial profile of the plasmon\nquasinormal modes, even at the single mode level. We exemplify the use of this\ntheory by calculating the Purcell factors of single quantum emitters, the\nelectron energy-loss spectroscopy spatial maps, as well as the Mollow triplet\nspectra of field-driven quantum dots with and without nonlocal effects for\ndifferent size nanoresonators. Our nonlocal quasinormal mode theory offers a\nreliable and efficient technique to study both classical and quantum optical\nproblems in nanoplasmonics.\n