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Double-layered metal grating for high-performance refractive index sensing.

Authors
  • Li, Guozhen
  • Shen, Yang
  • Xiao, Guohui
  • Jin, Chongjun
Type
Published Article
Journal
Optics Express
Publisher
The Optical Society
Publication Date
Apr 06, 2015
Volume
23
Issue
7
Pages
8995–9003
Identifiers
DOI: 10.1364/OE.23.008995
PMID: 25968735
Source
Medline
License
Unknown

Abstract

The detection of minuscule changes in the local refractive index by localized surface plasmon resonances (LSPRs), carried by metal nanostructures, has been used successfully in applications such as real-time and label-free detection of molecular binding events. However, localized plasmons demonstrate 1-2 orders of magnitude lower figure of merit (FOM) compared with their propagating counterparts. Here, we propose and experimentally demonstrate a high-performance refractive index sensor based on a structure of double-layered metal grating (DMG) with an FOM and FOM* reaching 38 and 40 respectively under normal incidence. Such a high FOM and FOM* arise from a result of a sharp fano resonance, which is caused by the coherent interference between the LSPR from the individual top gold stripes and Wood's anomaly (WA). Moreover, a small conformal decay length of ~68 nm is determined in DMG, indicating that the DMG is a promising candidate for label-free biomedical sensing.

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