The optics of the surface plasmon resonance has been known for a long time. In the configuration multilayer, the optical coupling of a wave incident to collective oscillations of electrons along an interface between a metal and a dielectric is governed by the thickness of metal and gap layers. The surface plasmon excitations excited by an electromagnetic wave in the visible band (λ= 633 nm). For the metal, in particular a frequency on their dielectric permittivity dependence and described by the Drude-Lorentz model and using the effectiveindex approach and an explicit expression for the propagation constant of gap surface plasmon polaritons (G-SPPs) obtained for moderate gap widths.
