Studies on Surface Polaritons in Ultrathin Films Sandwiched by Identical Dielectrics

We have investigated the spatial distribution of electric and magnetic fields and propagation characteristics of surface polaritons in ultrathin films with the thickness of less than 10 nm. The long-range surface polariton configuration, such as the dielectric/ultrathin film/dielectric geometry, was employed. For Ag thin film, the propagation lengths have been calculated by using effective dielectric constants evaluated from experiments or by a semi-empirical method. The propagation length monotonically increases with decreasing the thickness of Ag film. We have found that there is a sharp resonance in attenuated total reflection (ATR) spectra even for a s-polarized light.