We report experimental results on enhanced light transmission through double-layered(Ag/Au)metallic hole arrays within a skin-depth.Zero-order transmission spectrums are characterized as a function of Ag film's thickness,which extends fromδ/15,δ/6 to approximatelyδ,whereδis a skin-depth.In contrast with other reported results(Refs.[11-13])in single-layered metallic hole arrays,our experimental results show much more dramatic properties of transmission process dependent on sub-δthickness.It is shown that there is no negligible transmission enhancement atδ/15.Atδ/6,much higher transmission efficiency can be achieved.With film's thickness being close toδ,the transmission efficiency declines contrarily. Simultaneously,the corresponding resonant peak also slightly moves toward the shorter wavelength.It is proposed that the coupling of surface plasmon polaritons(SPPs)at Ag/Au interface withinδis involved in the process.
