Study Of Characteristics And Applications Of Surface Plasmon Resonance Sensing Based On Liquid Prism Coupling Method

Surface plasmon resonance(SPR) has become an important tool for chemical, biological and physical sensing applications. Based on monitoring of amplitude characteristics, the Kretschmann- Raether configuration with solid prism SPR sensors are widely discussed in current reports and commercialized. Phase-sensitive SPR has recently emerged as an upgrade of this technology to resolve the sensitivity issue. Profiting from a sharp phase jump under SPR and ultra-sensitive tools of its control, this technology offers 10~1000 times improvement of the detection limit. The SPR sensing system has been discussed for several decades, and the systems with high sensitivity, wide dynamic range, high signal to noise ratio, compact structure, micromation and micro-sample are always the goals of this field. A new liquid prism coupled SPR sensing configuration is proposed in this paper. The studies of the SPR sensing characteristics based on liquid prism coupled, the characteristics of the liquid prism coupled SPR configuration based on angular and phase interrogations, liquid prism SPR sensing configuration for the measurement of the chromatic dispersion of liquid and the liquid prism rather than sample SPR configuration are discussed based on the liquid prism configuration and electromagnetic theory.A simplified liquid prism SPR refractive index sensing configuration based on self adaptive angular interrogation is proposed. The glass substrate covered with metal film is used as the sensing chip; a hollow right angle box is used to take the liquid prism and the sample; the sensing chip is put on one side of the box; the glass is contacted with liquid and the metal film is contacted with air. The direction of the reflected light is constant when the sample box is turning, and this is benefit to adopt the angular interrogation. The liquid prism and the sample are consistent, and the structure of liquid prism SPR configuration is simplified compared with the solid prism based configuration. Compared with the conventional prism based configuration, the liquid prism SPR configuration has higher figure of merit with the same sample based on electromagnetic theory and Fresnel formulae.The method of liquid prism SPR refractive index sensing based on the angular and phase interrogations is proposed. The liquid prism as well as the sample SPR configuration is used in this method. The direction of the reflected light is constant, which is good to adopt the phase interrogation. The narrow full width at half maximum of the SPR dip can obtain the sharp phase curve. The reflectivity and the phase angle are all the functions of the incident angle based on the analysis with Fresnel formulae. The reflectivity of p polarized and the phase difference between p polarized and s polarized in different incident angle are obtained simultaneously. The characteristics include high sensitivity, wide dynamic range, high signal to noise ratio and simplified phase retrieved method of the SPR refractive index sensing are obtained from the liquid prism configuration based on the angular and phase interrogations. Meanwhile, the Michelson interferometer is used to retrieve the phase difference between s polarized and p polarized in a fixed incident angle. The lower error and high resolution are obtained with sine fitting of the experimental data.The application of the liquid prism SPR sensing configuration for the measurement of the chromatic dispersion of liquids is studied. The liquid prism as well as the sample configuration is used in this study. The collimated broadband light and the spectrograph are used in the experiments. Water as the standard sample is used to determine the real parts of the permittivity of Au film and Ag film. The chromatic dispersion curves of the samples include ethanol, n-hexane, simethicone, dichloromethane, diethylene glycol and glycerol are obtained from the above data and the wavelength interrogation in different incident angles. The experimental data of six samples are compared with the data of Abbe refractometer in different wavelengths, and the errors are in the reasonable range. The feasibility of the proposed configuration provided a new method to measure the chromatic dispersion of liquids with high sensitivity and fast response.The sensitivity and figure of merit of the liquid prism coupled Kretschmann SPR sensing configuration is discussed. The function of the liquid prism in this configuration is only the function of ‘prism’, and it is not the sample for detecting at the same time. The angular interrogation is used for analyzing the characteristics of this configuration. Because the refractive index of the liquid is continuous adjustable, different liquids are used as the prisms in the configuration to detect the same samples, and the conclusion that lower refractive index of liquid prism has higher sensitivity and figure of merit is obtained. Meanwhile, the SPR dip of air with water as the liquid prism is given, and the sensitivity and figure of merit of water prism are higher than that of solid prisms. The liquid prism coupled Kretschmann SPR sensing configuration provided a sensing application with high sensitivity and high figure of merit.