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Open AccessFeature PaperArticle

Improved Detection of Plasmon Waveguide Resonance Using Diverging Beam, Liquid Crystal Retarder, and Application to Lipid Orientation Determination

1
Department of Electrooptics and Photonics Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
2
CBMN, UMR 5248 CNRS, Université de Bordeaux, Allée Geoffroy St. Hilaire, 33600 Pessac, France
*
Authors to whom correspondence should be addressed.
Sensors 2019, 19(6), 1402; https://doi.org/10.3390/s19061402
Received: 28 February 2019 / Revised: 14 March 2019 / Accepted: 15 March 2019 / Published: 21 March 2019
(This article belongs to the Special Issue Advances in Plasmonic Sensing)
Plasmon waveguide resonance (PWR) sensors exhibit narrow resonances at the two orthogonal polarizations, transverse electric (TE) and transverse magnetic (TM), which are narrower by almost an order of a magnitude than the standard surface plasmon resonance (SPR), and thus the figure of merit is enhanced. This fact is useful for measuring optical anisotropy of materials on the surface and determining the orientation of molecules with high resolution. Using the diverging beam approach and a liquid crystal retarder, we present experimental results by simultaneous detection of TE and TM polarized resonances as well as using fast higher contrast serial detection with a variable liquid crystal retarder. While simultaneous detection makes the system simpler, a serial one has the advantage of obtaining a larger contrast of the resonances and thus an improved signal-to-noise ratio. Although the sensitivity of the PWR resonances is smaller than the standard SPR, the angular width is much smaller, and thus the figure of merit is improved. When the measurement methodology has a high enough angular resolution, as is the one presented here, the PWR becomes advantageous over other SPR modes. The possibility of carrying out exact numerical simulations for anisotropic molecules using the 4 × 4 matrix approach brings another advantage of the PWR over SPR on the possibility of extracting the orientation of molecules adsorbed to the surface. High sensitivity of the TE and TM signals to the anisotropic molecules orientation is found here, and comparison to the experimental data allowed detection of the orientation of lipids on the sensor surface. The molecular orientations cannot be fully determined from the TM polarization alone as in standard SPR, which underlines the additional advantage of the PWR technique. View Full-Text
Keywords: surface plasmon resonance; plasmon waveguide resonance; liquid crystal; biosensors surface plasmon resonance; plasmon waveguide resonance; liquid crystal; biosensors
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MDPI and ACS Style

Isaacs, S.; Harté, E.; D. Alves, I.; Abdulhalim, I. Improved Detection of Plasmon Waveguide Resonance Using Diverging Beam, Liquid Crystal Retarder, and Application to Lipid Orientation Determination. Sensors 2019, 19, 1402.

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