Planar three–layer sensor structures in the Kretschman configuration supporting the surface plasmon–polariton (SPP) modes are considered in the paper. The structures allow propagation of the SPP modes along the metal–solution interface and are aimed to detect ethanol dissolved in bulk water of various concentrations. Analysis of the resonance characteristics of the SPP mode and sensitivity of the spectral resonance response to changes in the refractive index of the water–ethanol solution is performed using the Fano approximation and effective medium theory in the visible and infrared regions. The spectral regions of maximum sensitivity to changes in the ethanol concentration are discovered. The obtained results open up the possibility of implementation the plasmon structures in sensors outside the water absorption regions and can also be used to design chemical sensors in monitoring of liquids.
$^1$Samara National Research University
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