Dresden 2017 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 20: Focussed Session: Frontiers in Exploring and Applying Plasmonic Systems II
(Joint Session of CPP, DS, HL, MM, and O, organized by DS)
DS 20.2: Topical Talk
Dienstag, 21. März 2017, 10:00–10:30, CHE 89
Transverse and Longitudinal Resonances in Plasmonic Gold Tapers — Surong Guo1, Nahid Talebi1, Wilfried Sigle1, Ralf Vogelgesang2, Gunther Richter3, Martin Esmann2, Simon F. Becker2, Christoph Lienau2, and •Peter A. van Aken1 — 1Max Planck Institute for Solid State Research, Stuttgart, Germany — 2Carl von Ossietzky University of Oldenburg, Oldenburg, Germany — 3Max Planck Institute for Intelligent Systems, Stuttgart, Germany
Conically-shaped metallic tapers are one of the most common structures with concomitant capabilities of nanofocusing and field enhancement. We distinguish two different dynamic mechanisms, reflection and phase matching, of surface plasmons excited by relativistic electrons in three-dimensional gold tapers with various opening angles from 5° to 47° which are studied both experimentally and theoretically, by means of electron energy-loss spectroscopy and finite-difference time-domain numerical calculations, respectively. We observe distinct resonances along the taper shaft independent of opening angles. We show that the origin of these resonances is different at different opening angles and results from a competition between two coexisting mechanisms. For large opening angles (> 20°), phase matching between the electron field and that of higher-order angular momentum modes is the dominant contribution because of the increasing interaction length between electron and the taper near-field. In contrast, reflection from the taper apex dominates at small opening angles (< 10°). A gradual transition of these two mechanisms is observed for intermediate opening angles.