Surface shape resonances of ridges on a thin film

The spectrum of surface shape resonances associated with a finite number of ridges on one interface of an otherwise plane film is calculated. The freq uencies are obtained numerically by solving the homogeneous integral equati ons which describe the electrostatic field in the vicinity of a surface def ect. The calculations are performed for a surface with ridges with Gaussian , Lorentzian and sinusoidal profiles. The results show a strong dependence of the localized plasmon frequencies on the surface profile; on the distanc e between the ridges, and on the thickness of the film.