title: Geometric interpretations for resonances of plasmonic nanoparticles.
abstract: The field of plasmonics can be roughly categorized into two branches: surface plasmon polaritons (SPPs) propagating in waveguides and localized surface plasmons (LSPs) supported by scattering particles. Investigations along these two directions usually employ different approaches, resulting in more or less a dogma that the two branches progress almost independently of each other, with few interactions. Here in this work we interpret LSPs from a Bohr model based geometric perspective relying on SPPs, thus establishing a connection between these two sub-fields. Besides the clear explanations of conventional scattering features of plasmonic nanoparticles, based on this geometric model we further demonstrate other anomalous scattering features (higher order modes supported at lower frequencies, and blueshift of the resonance with increasing particle sizes) and multiple electric resonances of the same order supported at different frequencies, which have been revealed to originate from backward SPP modes and multiple dispersion bands supported in the corresponding plasmonic waveguides, respectively. Inspired by this geometric model, it is also shown that, through solely geometric tuning, the absorption of each LSP resonance can be maximized to reach the single channel absorption limit, provided that the scattering and absorption rates are tuned to be equal.
authors.affiliation: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China.|Nonlinear Physics Centre, Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200, Australia.|The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Rupert F
authors.initials: RF
authors.lastname: Oulton
authors.affiliation: Nonlinear Physics Centre, Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Yuri S
authors.initials: YS
authors.lastname: Kivshar