Open AccessDouble-layered metal grating for high-performance refractive index sensing
Author(s) -
Guozhen Li,
Yang Shen,
Guoqing Xiao,
Jin Chen
Publication year - 2015
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.23.008995
Subject(s) - fano resonance , refractive index , figure of merit , optics , surface plasmon resonance , plasmon , materials science , grating , localized surface plasmon , surface plasmon , rigorous coupled wave analysis , resonance (particle physics) , optoelectronics , diffraction grating , physics , nanoparticle , nanotechnology , particle physics
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.