Resonant Excitation of Surface Electromagnetic Waves: An Analogy between Metallic Films and Gratings

Abstract
We show that near the resonant excitation of surface electromagnetic waves the amplitude of the reflected wave in a metallic film admits formally the same approximation as applies for gratings. Using this approximation it is easy to show that the phase exhibits different behaviour when the film thickness is above or below the critical value corresponding to the absorption of the reflected wave.