Predicting the Performance of Surface Plasmon Resonance Sensors Based on Anisotropic Substrates
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Predicting the Performance of Surface Plasmon Resonance Sensors Based on Anisotropic Substrates Eloise P. Rodrigues1
· Arthur A. Melo1 · Antonio M. N. Lima1
Received: 29 April 2020 / Accepted: 9 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The aim is to investigate how the sensing features of a surface plasmon resonance sensor based on the Kretschmann configuration are affected when the optical substrate is an anisotropic medium. The investigation considers the use of two different uniaxial anisotropic crystals, one made of barium titanate and another made of lithium niobate, as the optical substrate. It also considered that the sensor operates in the angular interrogation mode at the gold–water interface. The Fresnel equations and the finite element method were employed to determine the sensing features. The present study revealed that both formulations provide almost identical results for the resonance angle (difference less than 1%). On the other hand, the two formulations provide results with significant differences for additional features like the sensitivity and the full width at half maximum. Keywords Anisotropic medium · Surface plasmon resonance · Angular interrogation mode · Kretschmann configuration
Introduction Surface plasmon resonance (SPR) is a photoelectric phenomenon that occurs at the metal-dielectric interface when a p-polarized light (the electric field of the wave is normal to the plane of incidence) beam strikes the metallic surface [1]. It involves the charge oscillation of the electrons at the metal surface which, when in the resonance condition, confines the energy of the incident field at the interface, resulting in a significant loss of reflected light intensity. The resonance condition depends on the type of metallic layer and its related thickness, on the material used as the optical substrate, on the wavelength and angle of incidence of the incident light beam, among other aspects [2]. By augmenting the wave vector of incident photons by using prisms [3], waveguides [4], or even corrugated and periodic structures, such as diffractive gratings [5], one can create the proper coupling between the Eloise P. Rodrigues
[email protected] 1
Programa de P´os-Graduac¸a˜ o em Engenharia El´etrica (PPgEE), Centro de Engenharia El´etrica e Inform´atica (CEEI), Universidade Federal de Campina Grande (UFCG), Rua Apr´ıgio Veloso, 882, Universit´ario, Campina Grande, Para´ıba 58429–900, Brazil
surface plasmon wave (SPW) and the incident optical wave for the resonance to exist. Usually, the manufacture of these coupling devices is based on transparent, isotropic, and linear optical materials, which operate in the attenuated total reflection (ATR) mode. However, this condition is not easily achieved when the coupling devices are made of anisotropic and nonlinear optical materials. The main difficulty relies on the peculiarity of the electromagnetic wave propagation in this type of material. In an anisotropic and uniaxial (birefringent) medium, f
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