title: Revealing the subfemtosecond dynamics of orbital angular momentum in nanoplasmonic vortices.
abstract: The ability of light to carry and deliver orbital angular momentum (OAM) in the form of optical vortices has attracted much interest. The physical properties of light with a helical wavefront can be confined onto two-dimensional surfaces with subwavelength dimensions in the form of plasmonic vortices, opening avenues for thus far unknown light-matter interactions. Because of their extreme rotational velocity, the ultrafast dynamics of such vortices remained unexplored. Here we show the detailed spatiotemporal evolution of nanovortices using time-resolved two-photon photoemission electron microscopy. We observe both long- and short-range plasmonic vortices confined to deep subwavelength dimensions on the scale of 100 nanometers with nanometer spatial resolution and subfemtosecond time-step resolution. Finally, by measuring the angular velocity of the vortex, we directly extract the OAM magnitude of light.
authors.affiliation: Department of Electrical Engineering, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors.forename: G
authors.identifier: 0000-0002-3780-6759
authors.initials: G
authors.lastname: Spektor
authors.affiliation: Department of Physics and State Research Center for Optics and Materials Sciences (OPTIMAS), University of Kaiserslautern, Erwin Schroedinger Strasse 46, 67663 Kaiserslautern, Germany.|School of Physics, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: D
authors.initials: D
authors.lastname: Kilbane
authors.affiliation: Department of Physics and State Research Center for Optics and Materials Sciences (OPTIMAS), University of Kaiserslautern, Erwin Schroedinger Strasse 46, 67663 Kaiserslautern, Germany.
authors.forename: A K
authors.identifier: 0000-0001-5856-0367
authors.initials: AK
authors.lastname: Mahro
authors.affiliation: 4th Physics Institute and Stuttgart Center of Photonics Engineering (SCoPE), University of Stuttgart, D-70569 Stuttgart, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Frank
authors.affiliation: 4th Physics Institute and Stuttgart Center of Photonics Engineering (SCoPE), University of Stuttgart, D-70569 Stuttgart, Germany.
authors.forename: S
authors.identifier: 0000-0001-6334-4183
authors.initials: S
authors.lastname: Ristok
authors.affiliation: Department of Electrical Engineering, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors.forename: L
authors.identifier: 0000-0001-9047-766X
authors.initials: L
authors.lastname: Gal
authors.affiliation: Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Lotharstrasse 1-21, 47057 Duisburg, Germany.
authors.forename: P
authors.identifier: 0000-0003-2362-8645
authors.initials: P
authors.lastname: Kahl
authors.affiliation: Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Lotharstrasse 1-21, 47057 Duisburg, Germany.
authors.forename: D
authors.identifier: 0000-0002-6592-4146
authors.initials: D
authors.lastname: Podbiel
authors.affiliation: Department of Physics and State Research Center for Optics and Materials Sciences (OPTIMAS), University of Kaiserslautern, Erwin Schroedinger Strasse 46, 67663 Kaiserslautern, Germany.|I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Mathias
authors.affiliation: 4th Physics Institute and Stuttgart Center of Photonics Engineering (SCoPE), University of Stuttgart, D-70569 Stuttgart, Germany. h.giessen@pi4.uni-stuttgart.de meyerzh@uni-due.de meiro@ee.technion.ac.il ma@physik.uni-kl.de.
authors.forename: H
authors.identifier: 0000-0002-4270-3850
authors.initials: H
authors.lastname: Giessen
authors.affiliation: Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Lotharstrasse 1-21, 47057 Duisburg, Germany. h.giessen@pi4.uni-stuttgart.de meyerzh@uni-due.de meiro@ee.technion.ac.il ma@physik.uni-kl.de.
authors.forename: F-J
authors.identifier: 0000-0002-5878-2012
authors.initials: FJ
authors.lastname: Meyer Zu Heringdorf
authors.affiliation: Department of Electrical Engineering, Technion-Israel Institute of Technology, 32000 Haifa, Israel. h.giessen@pi4.uni-stuttgart.de meyerzh@uni-due.de meiro@ee.technion.ac.il ma@physik.uni-kl.de.
authors.forename: M
authors.identifier: 0000-0002-1644-4365
authors.initials: M
authors.lastname: Orenstein
authors.affiliation: Department of Physics and State Research Center for Optics and Materials Sciences (OPTIMAS), University of Kaiserslautern, Erwin Schroedinger Strasse 46, 67663 Kaiserslautern, Germany. h.giessen@pi4.uni-stuttgart.de meyerzh@uni-due.de meiro@ee.technion.ac.il ma@physik.uni-kl.de.
authors.forename: M
authors.identifier: 0000-0003-3413-5029
authors.initials: M
authors.lastname: Aeschlimann