Topological design approach for quadruple-ridge aperture configuration

We present a systematic approach for topological design of a high transmission metallic nano-aperture. The layout of the metallic layer is determined by the ON/OFF design method to maximize the norm value of the near-field intensity. Combined with the numerical finite element method, we derive a quadruple-ridge aperture composed of bowtie like shape with adjoining holes, and numerical results show that the location of the holes affects not only the transmission peak intensity, but also the field confinement because of the surface wave reflected from the adjoining holes. Results verify that the ON/OFF method to be a useful tool for obtaining an effective aperture shape.