Wavelength-tunable focal length of a nanopatterned metallicplanar lens with strong focusing capability

摘要

Numerical results for the spatial distributions of the light transmitted through metallic planar lenses composed of symmetric nanogroove arrays on the surfaces of a gold film deposited on a dielectric substrate are presented and explained. Both the near and far-field distributions of the intensity of light transmitted through such films, which are modeled by two aligned and reversed one-dimensional surface profile functions, are calculated by the use of a Green's function formalism. The focusing action obtained for different groove-width variations is investigated thoroughly. Results for an optimal transverse focus based on a quadratic variation of groove width across the array are also obtained, in addition to the effect of groove shape on the sharpness of planar lens focusing. Meanwhile, a significant dependence of the focal length on the wavelength of light incident from the air side through the gold film into a dielectric substrate is found for this detector configuration.