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O: Oberflächenphysik
O 23: Rastersondentechniken II
O 23.1: Vortrag
Dienstag, 9. März 2004, 15:45–16:00, H36
Near-field optical imaging of single molecules by means of a triangular aperture probe — •D. Molenda1, G. Colas des Francs1, U. C. Fischer1, H. Fuchs1, and A. Naber2 — 1Westfälische Wilhelms-Universität, 48149 Münster — 2Institut für Angewandte Physik, 76131 Karlsruhe
Recently we have introduced a triangular aperture probe for scanning near-field optical microscopy (SNOM) that combines a high optical resolution capability with a high transmission [1]. It turned out that the field pattern of such a probe is highly confined to only one side of the triangular aperture which is in strong contrast to a circular aperture. In order to further investigate the field pattern, we performed measurements of single dye molecules (TDI) embedded in a thin PMMA film. The aim was to map the electrical field components of the aperture in 3 dimensions by imaging a large number of randomly oriented molecular dipoles. The measured fluorescence patterns are compared with theoretical calculations which are based on a field-susceptibility technique. The calculated field patterns are in good agreement with the experiments and thus allow us to infer the dipole orientation of a molecule from the measured image. Due to the highly confined field of the triangular aperture probe we are able to demonstrate an optical resolution of 30 nm.
[1] A. Naber et al., Phys. Rev. Lett. 89, 210801 (2002).