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Letter

Tailoring Spatiotemporal Light Confinement in Single Plasmonic Nanoantennas

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Tobias Hanke†, Julijan Cesar†, Vanessa Knittel†, Andreas Trügler‡, Ulrich Hohenester‡, Alfred Leitenstorfer†, and Rudolf Bratschitsch*†

^† Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany

^‡ Institut für Physik, Karl-Franzens-Universität Graz, Universitätsplatz 5, 8010 Graz, Austria

Nano Lett., 2012, 12 (2), pp 992–996

DOI: 10.1021/nl2041047

Publication Date (Web): January 23, 2012

*E-mail: Rudolf.Bratschitsch@physik.tu-chemnitz.de.

§ Author Present Address

Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany.

Section:

Optical, Electron, and Mass Spectroscopy and Other Related Properties

Abstract

Plasmonic nanoantennas are efficient devices to concentrate light in spatial regions much smaller than the wavelength. Only recently, their ability to manipulate photons also on a femtosecond time scale has been harnessed. Nevertheless, designing the dynamical properties of optical antennas has been difficult since the relevant microscopic processes governing their ultrafast response have remained unclear. Here, we exploit frequency-resolved optical gating to directly investigate plasmon response times of different antenna geometries resonant in the near-infrared. Third-harmonic imaging is used in parallel to spatially monitor the plasmonic mode patterns. We find that the few-femtosecond dynamics of these nanodevices is dominated by radiative damping. A high efficiency for nonlinear frequency conversion is directly linked to long plasmon damping times. This single parameter explains the counterintuitive result that rod-type nanoantennas with minimum volume generate by far the strongest third-harmonic emission as compared to the more bulky geometries of bow-tie-, elliptical-, or disk-shaped specimens.