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Controlled Fano resonances via symmetry breaking in metamaterials for high-sensitive infrared spectroscopy
Author(s): Shuhei Hara; Atsushi Ishikawa; Takuo Tanaka; Yasuhiko Hayashi; Kenji Tsuruta
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Paper Abstract

A high-sensitive polarized surface-enhanced infrared absorption (polarized SEIRA) is proposed and demonstrated by utilizing the resonant coupling of Fano-resonant mode of the asymmetric metamaterials and IR vibrational mode of a polymer nano-film. The asymmetric metamaterials consisting of an Au nano-rod pair with a coupling nano-antenna were fabricated and characterized to demonstrate the controlled Fano resonances at 1730 cm-1, which spectrally overlapped with the C=O stretching vibrational mode. In the co-polarized SEIRA measurement, the C=O mode of the PMMA nano-film was clearly observed as a conventional anti-resonant peak within the Fano line-shape of the metamaterial. For the cross-polarized case, on the other hand, a distinctive dip appeared within a cross-polarized transmission peak of the metamaterial. Since the unwanted background is strongly suppressed in the cross-polarized detection scheme, the signal contrast was dramatically improved, allowing for the attomole detection of the C=O bond in the far-field measurement. Our metamaterial approach achieves the significant improvement of signal-to-background ratio in the far-field measurement, thus paving the way toward the high-sensitive analysis of functional group in direct IR spectroscopy.

Paper Details

Date Published: 16 September 2016
PDF: 5 pages
Proc. SPIE 9918, Metamaterials, Metadevices, and Metasystems 2016, 991814 (16 September 2016); doi: 10.1117/12.2237559
Show Author Affiliations
Shuhei Hara, Okayama Univ. (Japan)
Atsushi Ishikawa, Okayama Univ. (Japan)
RIKEN (Japan)
Takuo Tanaka, RIKEN (Japan)
Tokyo Institute of Technology (Japan)
Yasuhiko Hayashi, Okayama Univ. (Japan)
Kenji Tsuruta, Okayama Univ. (Japan)


Published in SPIE Proceedings Vol. 9918:
Metamaterials, Metadevices, and Metasystems 2016
Nader Engheta; Mikhail A. Noginov; Nikolay I. Zheludev, Editor(s)

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