Light transmission through nanostructured metallic films: coupling between surface waves and localized resonances.

We present an experimental and computational investigation of the optical properties of thin metallic films periodically perforated with nanometric apertures and show that high transmission through such a structure is attributable to the localized surface plasmon (LSP) resonances of the aperture. The periodicity-related optical phenomena, including Wood's anomaly and surface plasmon polariton (SPP) excitation, interfere with LSPs and generate Fano resonances with asymmetric spectral profiles. The transmission maximum of the Fano profile is related to the constructive interference between the LSP field and diffracted light propagating along the surface; the transmission minimum of the Fano profile is caused by the destructive interference between LSPs and SPPs. The study confirms the negative role of SPP in transmission through the structure.