Plasmonic nanoresonant materials

Resonant nano structure d metallic devices have attracted considerable recent attention through phenomena such as extraordinary transmission and their potential application as sensing elements, metamaterials and for enhancing nonlinear optical effects. Here we report on the investigation of the geometry and material properties on the performance of periodic and random arrays of coaxial apertures in thin metallic films. Such apertures in perfect conductors have been shown to resonate at a wavelength governed by the geometry of the apertures leading to enhanced transmission. This resonant wavelength is dictated by the cutoff wavelength of the fundamental mode propagating in the corresponding coaxial waveguide and, as a consequence, is largely independent of whether the apertures are isolated or in random or periodic arrangements. In the case of periodic samples, however, these resonances can coherently couple to surface waves to produce an analogue of the enhanced optical transmission seen in arrays of circular and other apertures. We have previously shown that as the width of the rings decreases, there are substantial red-shifts in the resonant wavelength from that predicted for perfect conductivity when the optical properties of the metal are considered. Here we report on recent developments in fabrication, design and modelling of metallic resonant structures and their near- and far-field optical characterisation. In particular, we consider the relationship between random and regular arrangements of apertures.