Electromagnetic far-and near-field excitations of rectangular microholes in gold films are investigated by means of a focused e beam. Radiative cavity modes, well below the surface plasmon (SP) frequency, are detected at exceptionally large distances and are shown to be strongly enhanced at near-field regions of selected slit walls due to hybridization with metal-supported SP polaritons. The proposed enhancement mechanism of such hybridized modes, found here to preserve the cutoff frequencies and symmetry characteristics of the pure waveguide modes, sheds light on the intriguing phenomenon of extraordinary optical transmission through subwavelength apertures in metallic films.
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics