Regensburg 2016 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 18: Plasmonics and Nanooptics I: Microscopy
HL 18.3: Talk
Monday, March 7, 2016, 15:45–16:00, S054
Improving the lateral near-field confinement in a nanofocusing SNOM — •Simon F. Becker1, Martin Esmann1, KyungWan Yoo1,2, Petra Groß1, Ralf Vogelgesang1, NamkYoo Park2, and Christoph Lienau1 — 1Carl von Ossietzky Universität, Oldenburg, Germany — 2Seoul National University, Seoul, Korea
The lateral near-field confinement in apertureless scanning near-field optical microscopy (SNOM) experiments is typically governed by the tip radius of the probe used. Here, we discuss how to improve the confinement beyond this limitation using a nanofocusing SNOM taper.
We approach such a taper [1,2] to a thin, semitransparent gold film. Angle-resolved images of elastically scattered radiation transmitted through the film [3,4] show a steep increase in the detected signal over the last few nanometers. We compare the experimental results to finite element method simulations and find this steep increase to be a clear signature of gap plasmon formation in the gap between tip and sample. The lateral confinement of these fields is proportional to the geometric mean of tip-sample distance and tip radius. Hence, gap plasmons may enable decreasing the confinement to sizes typically found for interaction cross-sections of single quantum emitters. Combining this spectrally broadband effect with the background-free detection available with nanofocusing SNOM seems promising for nanospectroscopic investigations of dense and heterogeneous quantum emitter systems.
[1] M.I. Stockman, PRL 93, 137404 (2004); [2] S. Schmidt et al., ACS Nano 6, 6040 (2012); [3] M. Esmann et al., BJ Nano 4, 603 (2013); [4] S.F. Becker et al., (submitted).