Bio -Sensor Based on S urface Plasmon Polariton: Study, Comparison and Optimization

In this paper, bio-sensors based on surface plasmon polariton, including plasmonic metals, such as gold and silver have been investigated. The functional principle of the sensing system is based on the shift in the minimum of reflectivity in glass/plasmonic metal/dielectric structure. For obtaining the surface plasmon polariton resonant excitation, the reflectivity of structure in the thicknesses of 10 to 80 nanometer of plasmonic metal is calculated and optimum thicknesses have been found. For gold and silver thin films, the minimum of reflectivity in thicknesses of 45 and 47.5 nm were obtained, respectively. In the following, sensitivity in optimum thicknesses has been investigated with more details. Glass/Au/Blood and Glass/Ag/Blood biosensors were shown 1.8 and 1.37 degree shift in minimum reflection for each 0.01 change in refractive index of blood, respectively. These results have proved that for gold included blood bio-sensor has an acceptable sensitivity which can be considered as a simple high sensitive bio-sensor