Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 11: Plasmonics and Nanooptics II: Microscopy
O 11.4: Vortrag
Montag, 7. März 2016, 16:00–16:15, S054
Coherent broadband nano-spectroscopy through plasmonic nanofocusing — •M. Esmann1, S.F. Becker1, H. Kollmann1, J. Witt1, K.W. Yoo1,2, A. Chimeh1, P. Groß1, R. Vogelgesang1, N.K. Park2, and C. Lienau1 — 1Carl von Ossietzky Universität, Oldenburg, Germany — 2Seoul National University, Seoul, Korea
Plasmonic nanofocusing microscopy enables broadband coherent light scattering spectroscopy with 5 nm spatial resolution. This is used to image optical near-fields around individual metallic nanoparticles. Conceptually, surface plasmon polaritons are launched by a grating coupler on a conical metallic taper and propagate towards the taper apex where they are transformed into highly confined near-fields [1-3]. Upon optical interaction with a sample, far-fields scattered from the apex are collected almost background free. Here, we use coherent white light to excite this isolated, spectrally broadband nano-lightsource at the apex of a monocrystalline gold taper. We then investigate both the spectral and spatial characteristics of optical near-fields around chemically synthesized gold nanorods. We find dipolar plasmon resonances with comparatively high Q-factors of up to 15. These are confirmed by far-field measurements. We simultaneously also image the corresponding near-field pattern in the spatial domain and achieve spatial resolution down to 5 nm. As these measurements are fully coherent, they can be straightforwardly extended to the investigation of coherences in biological or semiconducting systems.
[1] M.I. Stockman, PRL 93, 137404 (2004); [2] S. Schmidt et al., ACS Nano 6, 6040 (2012); [3] M. Esmann et al., BJNANO 4, 603 (2013).