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HL: Fachverband Halbleiterphysik

HL 61: Plasmonics and Nanooptics VII: Applications and Other Aspects

HL 61.5: Vortrag

Mittwoch, 22. März 2017, 16:00–16:15, TRE Ma

Ultrafast imaging of electric fields around nanostructures — •Jan Vogelsang, Germann Hergert, Petra Groß, and Christoph Lienau — Institut für Physik, Carl von Ossietzky Universität, 26129 Oldenburg, Germany

The combination of high spatial resolution electron microscopes and high temporal resolution laser spectroscopy promises experiments in unexplored spatio-temporal regimes. E.g., many fundamental photoinduced processes such as coherent charge and energy transport phenomena occur on few-fs time scales. However, in today's ultrafast electron microscopes the time resolution is so far limited to ~100fs: The electrons propagate over mesoscopic distances, which gives rise to electron pulse broadening due to dispersion.

Recently, we demonstrated a new, plasmon-driven electron source that tackles this challenge: Adiabatic nanofocusing of surface plasmons on sharply etched metallic tapers concentrates light in a nanometric volume and efficiently induces electron emission. Direct illumination of the emission site is avoided and hence the apex-sample-distance can be chosen arbitrarily small (Nano Lett. 15, 4685, 2015).

Here, we show first ultrafast electron micrographs with few-nm spatial and few-ten-fs temporal resolution. We record an ultrafast change of the electric field near carbon nanostructures after laser excitation. It deflects the probing electrons which directly maps the field distribution to the 2d electron detector. The results prove that the simple, but efficient working principle of a lensless point-projection microscope is ideal for maintaining the ultrashort duration of electron pulses.