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Q: Fachverband Quantenoptik und Photonik
Q 34: Ultrashort laser pulses: Applications
Q 34.6: Talk
Tuesday, March 19, 2013, 15:15–15:30, F 142
Nanoscale probing of optical field enhancement by electron rescattering — •Sebastian Thomas1, Michael Krüger1, Michael Förster1, Markus Schenk1, and Peter Hommelhoff1,2 — 1Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Gemany — 2Universität Erlangen-Nürnberg, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany
The enhancement of optical electric fields in the vicinity of nanostructures enables the localization of electromagnetic energy on the nanoscale. We present a new method of measuring the local field with a resolution of 1 nm. Experimentally, we study the photoemission of electrons from a metal nanotip under laser illumination. In this setup, some of the emitted electrons return to and scatter from the tip surface within one optical cycle of the driving field [1]. By measuring the kinetic energy of these electrons, we obtain the enhanced field strength within 1 nm from the tip surface [2]. A comparison with the field strength we calculate from focal and laser parameters yields the field enhancement factor. Our results are in good agreement with Maxwell simulations.
The resolution of 1 nm is about an order of magnitude better than previous work [3] and close to the length scale of quantum plasmonics, where quantum mechanical effects near the tip surface are expected to reduce the local field strength [4]. We discuss the implications.
[1] M. Krüger, M. Schenk, P. Hommelhoff, Nature 475, 78 (2011)
[2] S. Thomas et al., arxiv:1209.5195 (2012)
[3] M. Raschke et al., ChemPhysChem 6, 2197 (2005)
[4] J. Zuloaga, E. Prodan, P. Nordlander, ACS Nano 4, 5269 (2010)