title: Nanoscale Imaging of Local Few-Femtosecond Near-Field Dynamics within a Single Plasmonic Nanoantenna.
abstract: The local enhancement of few-cycle laser pulses by plasmonic nanostructures opens up for spatiotemporal control of optical interactions on a nanometer and few-femtosecond scale. However, spatially resolved characterization of few-cycle plasmon dynamics poses a major challenge due to the extreme length and time scales involved. In this Letter, we experimentally demonstrate local variations in the dynamics during the few strongest cycles of plasmon-enhanced fields within individual rice-shaped silver nanoparticles. This was done using 5.5 fs laser pulses in an interferometric time-resolved photoemission electron microscopy setup. The experiments are supported by finite-difference time-domain simulations of similar silver structures. The observed differences in the field dynamics across a single particle do not reflect differences in plasmon resonance frequency or dephasing time. They instead arise from a combination of retardation effects and the coherent superposition between multiple plasmon modes of the particle, inherent to a few-cycle pulse excitation. The ability to detect and predict local variations in the few-femtosecond time evolution of multimode coherent plasmon excitations in rationally synthesized nanoparticles can be used in the tailoring of nanostructures for ultrafast and nonlinear plasmonics.
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Mårsell
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Arthur
authors.initials: A
authors.lastname: Losquin
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Robin
authors.initials: R
authors.lastname: Svärd
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Miguel
authors.initials: M
authors.lastname: Miranda
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Chen
authors.initials: C
authors.lastname: Guo
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Anne
authors.initials: A
authors.lastname: Harth
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Lorek
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Mauritsson
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Cord L
authors.initials: CL
authors.lastname: Arnold
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.|School of Physics and Technology, and Institute for Advanced Studies, Wuhan University , Wuhan 430072, China.
authors.forename: Hongxing
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Anne
authors.initials: A
authors.lastname: L'Huillier
authors.affiliation: Department of Physics, Lund University , P.O. Box 118, 221 00 Lund, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Mikkelsen
mesh_terms: D008855:Microscopy, Electron, Scanning; D049329:Nanostructures
keywords: ITR-PEEM; multipolar surface plasmons; nanorice; optical antennas; surface plasmon retardation; ultrafast plasmonics