Signal Processing Based On SPR Sensor

Surface Plasmon Resonance is a type phenomenon of Physical optics.An evanescent wave is produced by a light beam suffering total internal reflection at the interface between glass and metal film. The evanescent wave penetrates into the metal film and excites surface plasmon wave. At certain incident angle of light or wavelength, the vector for evanescent wave will match the vector for surface plasmon wave and thus result in a resonance. Surface Plasmon wave, which oscillates and propagates along the upper surface of the metal film, absorbs some energy of the incident polarized light from the evanescent wave, and cause a decrease of the total internal reflected light intensity. The exact location of the resonance peak of reflected light can be determined using a charge coupled device (CCD) detector. The binding of molecules onto the upper metal surface causes a change in refractive index of the surface medium that can be observed as a shift in resonant angle or wavelength. This shift can be used in the identification of refractive index of interested samples. The main contents are as follows:(1) The fundamental principle of SPR sensors is presented. The main background of our work and the new progress of SPR sensor technology are briefly discussed.(2) The theory of surface plasmon wave is formulated. The condition for SPR is presented. Based on the structure of SPR sensor, the influence of some parameters (FWHM of light source, the thickness of the film, and the central wavelength of light source et al.) on the performance of sensor is investigated.(3) The detailed function of every component of the senor is discussed. The digital characteristics of output are analyzed and the mathematical methods of data processing based on the characteristics are investigated.(4) In order to enhance the sensitivity and the resolution of the SPR sensor, the noise of the CCD should be reduced as much as possible. Wavelet analysis is considered as a very useful tool for reducing of the effect of the noises. The concept and application of Wavelet analysis is briefly discussed. The wavelet, one of powerful tools for ameliorating the signal to noise rate, is creatively introduced into the SPR research. The noise can be removed from the signal and the smoothed SPR spectra are obtained without any distortion.