Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 23: Symposium: Ultrafast Nanooptics III
O 23.3: Vortrag
Dienstag, 27. März 2007, 11:45–12:00, H38
Light confinement via grating coupling of surface plasmons onto nanoscopic metal tips — •Claus Ropers1, Catalin Neacsu1, Thomas Elsässer1, Martin Albrecht2, Markus Raschke1,3, and Christoph Lienau1,4 — 1Max-Born-Institut, D-12489 Berlin — 2Institut für Kristallzüchtung, D-12489 Berlin — 3Department of Chemistry, University of Washington, Seattle, WA 98195-1700 — 4Institut für Physik, Carl von Ossietzky Universität Oldenburg, D-26129 Oldenburg
Localized and delocalized surface plasmon polaritons (SPPs) promise an unprecedented amount of microscopic light control and confinement. Structuring the surface of metals with nanometer precision allows for a tailoring of the SPP excitation and propagation. This may lead to new forms of nano-focusing, as proposed theoretically for tapered SPP waveguides. In this context, the achievement of highly localized light at the apex of a metal nano-tip is particularly desirable, as currently most apertureless near-field optical techniques are affected by considerable far-field background light.
Here, we realize a local femtosecond light source by focusing SPPs on nano-fabricated metallic tips with with radii down to 10 nm. By the use of focused ion beam milling, one-dimensional gratings are written onto the tip shaft, several micrometers away from the apex. Illumination of the grating with a broadband 7-fs Ti-sapphire oscillator leads to resonant excitation of SPPs, which travel to the tip apex and are reradiated. The clear spatial separation of the excitation from the tip end carries great potential as a novel light source in near-field microscopy.