Analyzing extraordinary optical transmission phenomenon by a vertical mode expansion method

An efficient numerical method is developed to analyze light transmission through subwavelength apertures in metallic films, where the apertutres can have arbitrary cross sections and be surrounded by many grooves. The method is tailor-made for three-dimensional structures that are layered in different regions. It relies on field expansions in one-dimensional vertical modes, and boundary integral equations or cylindrical wave expansions for two-dimensional Helmholtz equations.