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Proceedings Paper

Fano lineshapes of 'Peak-tracking chip' spatial profiles analyzed with correlation analysis for bioarray imaging and refractive index sensing
Author(s): K. Bougot-Robin; S. Li; W. Yue; L. Q. Chen; X. X. Zhang; W. J. Wen; H. Benisty
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Paper Abstract

The asymmetric Fano resonance lineshapes, resulting from interference between background and a resonant scattering, is archetypal in resonant waveguide grating (RWG) reflectivity. Resonant profile shift resulting from a change of refractive index (from fluid medium or biomolecules at the chip surface) is classically used to perform label-free sensing. Lineshapes are sometimes sampled at discretized “detuning” values to relax instrumental demands, the highest reflectivity element giving a coarse resonance estimate. A finer extraction, needed to increase sensor sensitivity, can be obtained using a correlation approach, correlating the sensed signal to a zero-shifted reference signal. Fabrication process is presented leading to discrete Fano profiles. Our findings are illustrated with resonance profiles from silicon nitride RWGs operated at visible wavelengths. We recently demonstrated that direct imaging multi-assay RWGs sensing may be rendered more reliable using “chirped” RWG chips, by varying a RWG structure parameter. Then, the spatial reflectivity profiles of tracks composed of RWGs units with slowly varying filling factor (thus slowly varying resonance condition) are measured under monochromatic conditions. Extracting the resonance location using spatial Fano profiles allows multiplex refractive index based sensing. Discretization and sensitivity are discussed both through simulation and experiment for different filling factor variation, here Δf=0.0222 and Δf=0.0089. This scheme based on a “Peak-tracking chip” demonstrates a new technique for bioarray imaging using a simpler set-up that maintains high performance with cheap lenses, with down to Δn=2×10-5 RIU sensitivity for the highest sampling of Fano lineshapes.

Paper Details

Date Published: 22 May 2013
PDF: 7 pages
Proc. SPIE 8767, Integrated Photonics: Materials, Devices, and Applications II, 876703 (22 May 2013); doi: 10.1117/12.2018316
Show Author Affiliations
K. Bougot-Robin, Hong Kong Univ. of Science and Technology (Hong Kong, China)
S. Li, Hong Kong Univ. of Science and Technology (Hong Kong, China)
W. Yue, King Abdullah Univ. of Science and Technology (Saudi Arabia)
L. Q. Chen, King Abdullah Univ. of Science and Technology (Saudi Arabia)
X. X. Zhang, King Abdullah Univ. of Science and Technology (Saudi Arabia)
W. J. Wen, Hong Kong Univ. of Science and Technology (Hong Kong, China)
KAUST-HKUST Micro/Nanofluidic Joint Lab. (Hong Kong, China)
H. Benisty, Lab. Charles Fabry, CNRS, Univ. Paris Sud (France)


Published in SPIE Proceedings Vol. 8767:
Integrated Photonics: Materials, Devices, and Applications II
Jean-Marc Fédéli; Laurent Vivien; Meint K. Smit, Editor(s)

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