Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 50: Plasmonics & Nanooptics III: STM and Time-Resolved Methods (joint session O/CPP)

O 50.7: Vortrag

Mittwoch, 3. April 2019, 12:00–12:15, H8

Dynamic imaging of plasmonic nanostructures with an ultrafast point-projection electron microscope — •Germann Hergert¹, Andreas Wöste¹, Jan Vogelsang¹, Dong Wang², Petra Groß¹, and Christoph Lienau¹ — ¹Institut für Physik, Carl von Ossietzky Universität, 26129 Oldenburg, Germany — ²Institut für Werkstofftechnik, TU Ilmenau, 98693, Germany

The motion of electrons inside metallic nanostructures defines their optical properties. The study of this electron motion requires microscopes with few-fs time and nm-spatial resolution. Ultrafast electron microscopy (UEM) is a promising approach towards this goal, combining the spatial resolution of electron microscopes with the temporal resolution of ultrashort laser pulses. So far, the mesoscopic distance between sample and electron emitter limits the temporal resolution in UEM to 100fs.

We solve this problem with a novel electron source in form of a conical gold taper, without direct illumination of the apex. Light is coupled to surface plasmons on the shaft of the tip, which propagate towards the apex, where they cause electron emission.

Implementing this source in our ultrafast point-projection microscope allows minimal sample-emitter distances and therefore enhanced temporal resolution of 20fs [1]. We use this microscope to observe the ultrafast expansion of a photoemitted electron cloud inside a plasmonic nanoresonator in real space, and in addition, we observe a streaking of the probing electrons by the photoemitted charges.

[1] J. Vogelsang et al., Light: Science & Applications 7, 55 (2018)