Spectral interferometry-based surface plasmon resonance sensing of liquid analyte refractive index change

Theoretical study of a polarimetric setup intended to measure the refractive index change of a liquid analyte is presented. The detection scheme is based on the excitation of surface plasmon resonance in Kretschmann configuration combined with spectral interferometry. The principle of the method is to observe the spectral interference fringes as a result of mixing of two orthogonal linearly polarized waves with an analyzer. The waves are reflected from the base of a coupling prism covered by a thin metal layer used for generation of surface plasmon waves. The polarimetric setup consists of a linear polarizer, a birefringent crystal, a SF10 coupling prism covered by a gold layer and a linear analyzer. The attenuated total reflection at the prism base serves for the excitation of surface plasmon waves. The output optical field is then analyzed by a spectrometer. The phase change of resulting interference spectrum contains the information about the refractive index change of investigated analyte. The shift of phase curve is related to the analyte refractive index change. The model computation is performed in the frame of thin-film optics and the dispersion properties of all included materials are taken into account.