Theoretical Analysis of Multilayer Surface Plasmon Resonance Sensors Using Thin-Film Optical Admittance Formalism

A theoretical analysis of surface plasmon resonance (SPR) behavior of conventional Ag sensor within the Kretschmann configuration is reported using thin-film optical admittance formalism. We examine the additional layer thickness and refractive index effects on optical admittance by considering Ag/SiO2, Ag/TiO2, and Ag/Si sensors. Theoretical results show that imaginary part of admittance is more sensitive to the sensing medium refractive index change than its real part, and a maximum of angular sensitivity reached by the sensors may be obtained simply by calculating the shift of the incident angle corresponding to the minimum of admittance imaginary parts.