Finite-difference time-domain studies of light transmission through nanohole structures

We present theoretical studies on the transmission of light through subwavelength, circular apertures surrounded by circular groove structures. Finite-difference time-domain equations in cylindrical coordinates are provided for both dispersive materials and electrical conductors. The nanohole systems are composed of a circular hole in a slab, that is encircled by sinusoidal grooves defined by a period and depth. Light transmission is found to be extremely sensitive to the hole size, groove period, and groove depth. We determine a set of groove parameters that optimize transmission. Enhancements in transmission by approximately a factor of four can be achieved for silver in the visible when compared to the light incident upon the hole. These results may find utility in the design of nanoscale light manipulating devices. PACS 73.20.Mf; 78.20.Ci; 78.68.+m; 64.47.-n; 03.50.De