Imaging the Hidden Modes of Ultrathin Plasmonic Strip Antennas by Cathodoluminescence

Type
Article

Authors
Barnard, Edward S.
Coenen, Toon
Vesseur, Ernst Jan R.
Polman, Albert
Brongersma, Mark L.

KAUST Grant Number
KUS-C1-015-21

Date
2011-10-12

Abstract
We perform spectrally resolved cathodoluminescence (CL) imaging nanoscopy using a 30 keV electron beam to identify the resonant modes of an ultrathin (20 nm), laterally tapered plasmonic Ag nanostrip antenna. We resolve with deep-subwavelength resolution four antenna resonances (resonance orders m = 2-5) that are ascribed to surface plasmon polariton standing waves that are confined on the strip. We map the local density of states on the strip surface and show that it has contributions from symmetric and antisymmetric surface plasmon polariton modes, each with a very different mode index. This work illustrates the power of CL experiments that can visualize hidden modes that for symmetry reasons have been elusive in optical light scattering experiments. © 2011 American Chemical Society.

Citation
Barnard ES, Coenen T, Vesseur EJR, Polman A, Brongersma ML (2011) Imaging the Hidden Modes of Ultrathin Plasmonic Strip Antennas by Cathodoluminescence. Nano Lett 11: 4265–4269. Available: http://dx.doi.org/10.1021/nl202256k.

Acknowledgements
The authors would like to thank Ragip A. Pala for assistance in preparation of the samples used in this work. The Stanford part of this work is supported by the Center for Advanced Molecular Photovoltaics (Award No KUS-C1-015-21), made by King Abdullah University of Science and Technology (KAUST). CL experiments were performed at AMOLF and are part of the research program of FOM that is financially supported by NWO. Work at AMOLF is also supported by NanoNextNL, a nanotechnology program of the Dutch Ministry of Economic Affairs. It is also part of the research program “Microscopy and modification of nanostructures with focused electron and ion beams” that is cofinanced by FEI Company.

Publisher
American Chemical Society (ACS)

Journal
Nano Letters

DOI
10.1021/nl202256k

PubMed ID
21879729

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