Numerical Analysis of Grating and Prism Coupled Surface Plasmon Resonance

The main purpose of the paper consists of presenting simulation results obtained in analyzing the surface plasmons excitation effect, presently commonly referred as surface plasmon resonance (SPR) and its main possible application as a highly accurate and sensitive sensor. Both electromagnetic wave coupling configurations to the medium, grating and Kretschmann prism configurations are investigated. In the grating coupling configuration, the performed numerical simulations are pointing mainly to nanowire and/or nanostructured gratings. The numerically simulation model developed in the case of the grating coupling configuration consider Cu, Au, Ag or other metal nanowire having a diameter of 40 nm to 800 nm, formed on dielectric substrates with a refractive index between 1.4 and 2.4, such as SF11, BK7 glasses, GaP and TiO2-o (rutile). The same range of dielectric materials is considered for the prism coupling configuration. The thin layers formed on the face of prism coupler is considered as being formed by up to 15 Cu, Au, Ag or other metal layers. Several shapes of the groves formed onto the high refractive index substrate are investigated, such as square/rectangular (including the rounded corner case), circular or elliptical. As the low-index background material air, water and sea-water were considered. In order to get more insight into the plane electromagnetic wave propagation in such waveguides a simulation procedure is developed on the basis of the Finite Element and Finite Difference Time Domain methods and a finite element Helmholtz solver. For practical applications, it is of interest to evaluate how much electromagnetic radiation can be coupled into the medium. Therefore, the coupling coefficient of electromagnetic radiation from and into the medium using the grating and Kretschmann prism coupling configurations has been examined.