Enhanced light transmission through cascaded metal films perforated with periodic hole arrays

We report experimental results on enhanced light transmission through two periodically perforated metal films separated by a layer of dielectric. A perforated metal film (single metallic structure) exhibits extraordinary optical transmission, and when two such perforated metal films are spaced by a dielectric layer (cascaded metallic structure), the transmission is further increased. The maximum transmission of the cascaded metallic structure, which depends on the distance between the two metal films, can be more than 400% greater than that of a corresponding single metallic structure. It is proposed that the coupling of surface plasmon polaritons between the two metal films is involved in the process.