Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 86: Plasmonics and Nanooptics VI
O 86.7: Talk
Friday, March 15, 2013, 12:00–12:15, H36
Probing optical near-fields by photoemission of electrons with 1 nm resolution — •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
We present a new method of measuring optical near-field enhancement. In our experiments, we use a metal nanotip under laser illumination as an ultrafast source of photoelectrons. Some of the emitted electrons return to the tip surface within one optical cycle of the driving field, where they may gain energy by elastic rescattering [1]. This process crucially depends on the electric field strength in the immediate vicinity of the surface. By measuring the kinetic energy of rescattered electrons, we obtain the enhanced electric field strength within 1 nm from the tip surface [2]. This is close to the length scale of quantum plasmonics, and about an order of magnitude better than the previous record resolution [3].
Our results for the field enhancement factor at tungsten and gold tips are in good agreement with Maxwell simulations. Further simulations of nanotips with varying dielectric function give insight into the plasmonic characteristics of nanotips, which differ significantly from those of nanospheres.
[1] Krüger, Schenk, Hommelhoff, Nature 475, 78 (2011)
[2] Thomas et al., arxiv:1209.5195 (2012)
[3] Raschke et al., ChemPhysChem 6, 2197 (2005)