title: Photoelectron imaging of modal interference in plasmonic whispering gallery cavities.
abstract: We use three-photon photoemission electron microscopy (PEEM) to investigate the interference of coherently excited dipolar and quadrupolar resonant modes of plasmonic whispering gallery resonators formed by circular grooves patterned into a flat Au surface. Optical scattering and cathodoluminescence spectroscopy are used to characterize the cavity resonance spectra for a wide range of cavity radii and groove depths. Using PEEM, we directly resolve the interference between the modal field distribution of dipolar and quadrupolar modes that are coherently excited at λ = 795 nm under oblique incidence. Characteristic asymmetries in the photoelectron images for both TM and TE excitation are a direct consequence of the coherent excitation of the resonant modes.
authors.forename: Pascal
authors.initials: P
authors.lastname: Melchior
authors.forename: Deirdre
authors.initials: D
authors.lastname: Kilbane
authors.forename: Ernst Jan
authors.initials: EJ
authors.lastname: Vesseur
authors.forename: Albert
authors.initials: A
authors.lastname: Polman
authors.forename: Martin
authors.initials: M
authors.lastname: Aeschlimann