Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 7: Plasmonics and Nanooptics I
O 7.2: Talk
Monday, March 11, 2013, 10:45–11:00, H31
Quantitative mapping of plasmonic near-field intensity using infrared far-field vibrational spectroscopy — •Daniel Dregely1, Frank Neubrech1, Huigao Duan2, and Harald Giessen1 — 14th Physics Institute and Research Center SCoPE, University of Stuttgart, Germany — 2Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, Hunan University, P.R. China
Nanoantennas confine electromagnetic fields at visible and infrared wavelengths to volumes of only a few cubic nanometers. Assessing their near-field distribution offers fundamental insight into light-matter coupling and is of special interest for applications such as radiation engineering, attomolar sensing, antenna enhanced vibrational spectroscopy [1], and nonlinear optics. Most experimental approaches to measure near-fields employ either diffraction-limited far-field methods or intricate near-field scanning techniques. Here, by diffraction-unlimited far-field spectroscopy in the infrared, we map the intensity of the electric field in the vicinity of plasmonic nanoantennas with 10 nm spatial accuracy. Specifically, we place a patch of probe molecules at different locations in the near-field of a resonant antenna and extract the molecular vibrational excitation. We map the field intensity along a dipole antenna and confirm our findings with numerical simulations. Furthermore, we quantify the near-field intensity of a gap-type antenna, observing a 5.9 times vibrational strength enhancement inside the gap.
[1] F. Neubrech et al., Phys. Rev. Lett. 101, 157403 (2008).