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Proceedings Paper

Role of local fields and defects in the nonlinear response of metal nanostructures
Author(s): Martti Kauranen; Hannu Husu; Sami Kujala; Brian K. Canfield; Janne Laukkanen; Benfeng Bai; Markku Kuittinen; Jari Turunen; Juha Kontio; Jukka Viheriälä; Tapio Niemi; Eric Chandler; Jeff A. Squier
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Paper Abstract

We show that local fields associated both with overall structural features and with unintended defects can be important in the second-order nonlinear response of metal nanostructures. We first consider noncentrosymmetric T-shaped gold nanodimers with nanogaps of varying size. The reflection symmetry of the T-shape is broken by a small slant in the mutual orientations of the horizontal and vertical bars, which makes the sample chiral and gives rise to a different nonlinear response for left- and right-hand circularly-polarized fundamental light. Measurements of achiral and chiral second-harmonic signals as well as the circular-difference response exhibit a nontrivial dependence on the gap size. All results are explained by considering the distribution of the resonant fundamental field in the structure and its interaction with the surface nonlinearity of the metal. We also prepared arrays of ideally centrosymmetric circular nanodots. Second- and third-harmonic generation microscopies at normal incidence were used to address polarization-dependent responses of individual dots. Both signals exhibit large differences between individual dots. This is expected for second-harmonic generation, which must arise from symmetry-breaking defects. However, similar results for third-harmonic generation suggest that both nonlinear responses are dominated by strongly localized fields at defects.

Paper Details

Date Published: 26 August 2008
PDF: 10 pages
Proc. SPIE 7032, Plasmonics: Metallic Nanostructures and Their Optical Properties VI, 70321J (26 August 2008); doi: 10.1117/12.794220
Show Author Affiliations
Martti Kauranen, Tampere Univ. of Technology (Finland)
Hannu Husu, Tampere Univ. of Technology (Finland)
Sami Kujala, Tampere Univ. of Technology (Finland)
Brian K. Canfield, Tampere Univ. of Technology (Finland)
Janne Laukkanen, Univ. of Joensuu (Finland)
Benfeng Bai, Univ. of Joensuu (Finland)
Markku Kuittinen, Univ. of Joensuu (Finland)
Jari Turunen, Univ. of Joensuu (Finland)
Juha Kontio, Tampere Univ. of Technology (Finland)
Jukka Viheriälä, Tampere Univ. of Technology (Finland)
Tapio Niemi, Tampere Univ. of Technology (Finland)
Eric Chandler, Colorado School of Mines (United States)
Jeff A. Squier, Colorado School of Mines (United States)

Published in SPIE Proceedings Vol. 7032:
Plasmonics: Metallic Nanostructures and Their Optical Properties VI
Mark I. Stockman, Editor(s)

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