Surface plasmon resonance based sensing of aqueous solutions using spectral interferometry

Abstract

This paper deals with a polarimetric setup to measure the refractive index change of aqueous solutions. The experimental method is based on the surface plasmon resonance effect in the Kretschmann configuration combined with spectral interferometry. In order to retrieve surface plasmon resonance-induced differential phase change, a windowed Fourier transform was adopted to extract the phases from two spectral interferograms, one corresponding to the reference material (air) and the second to the analyte (NaCl aqueous solution). The shift of phase curve is related to the analyte refractive index change. The refractive index of the NaCl aqueous solutions (0, 2 and 5 percent) was measured by the Abbe refractometer at a wavelength of 589.3 nm and compared with theoretical one, calculated by the Lorentz–Lorenz equation. An excellent agreement between the values was confirmed. The resonance wavelengths as extremes of the surface plasmon resonance-induced differential phase changes retrieved from spectral interference signals were compared with the resonance wavelengths determined from spectral reflectance measurements. A good agreement between the values was confirmed.