Standing-wave surface-plasmon resonances with overhanging zero-order metal gratings

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Abstract
We have found that a relatively unknown and little understood type of standing-wave surface-plasmon resonance may be excited in strongly blazed overhanging zero-order metallic gratings. A modeling code based on an oblique coordinate transformation has been implemented to evaluate the optical response of these structures. For certain dimensions of surface topography, very strong resonant absorption of light is found that is insensitive to the angle of incidence yet is sharply wavelength selective. These resonances are not the well-known geometrical cavity resonances but have smaller periodicities determined by the self-coupling of surface-plasmon modes on the overhanging surfaces.