Three-dimensional structures for enhanced transmission through a metallic film: Annular aperture arrays

Light transmission through arranged nanostructures can be increased comparing to what was observed three years ago by Ebbesen [Nature, 391, 667 (1998)]. The results obtained recently by Krishnan [Opt. Commun. 200, 1 (2001)] with gold hole grating are confirmed, but a new design is suggested in order to enhance the light transmission. A three-dimensional finite difference time domain simulation was performed in order to obtain the spectral response of metallic periodic structures in the visible domain. The grating structure is modified by filling the central region of each hole with a concentric cylinder of smaller diameter. The grating now consists of a periodic array of annular apertures. Theoretical simulations were performed with such a subwavelength silver grating. It is shown that the transmission efficiency can reach 80% in the visible spectral range.