Surface-plasmon-enhanced light transmission through planar metallic films

We show experimental results for the optical transmission of planar metallic films closely coupled to periodic subwavelength structures; exceptionally high transmission levels (up to 39%) are measured for these otherwise-opaque films. The measured dispersion of the transmission maxima agrees well with the theoretical dispersion of surface plasmon polariton (SPP) modes on a planar metal film, which strongly suggests that the excitation of these SPP modes is responsible for the exceptional transmission features. This is further supported by rigorous coupled wave analysis simulations. The overall transmission is a result of the coupling between the incident light and the SPP modes, as well as the localized surface plasmon modes within the structure.