Metal nanolens transforming far-field into far-field

In this communication we present technical details of performance of recently proposed silver nanolens which transforms a far-field source into a far-field focus [P. Wrobel, J. Pniewski, T.J. Antosiewicz, T. Szoplik, ldquoFocusing radially polarized light by concentrically corrugated silver film without a holerdquo Phys. Rev. Lett., in print (2009)]. The nano-lens is a free standing silver nanolayer with no hole on the optical axis and double-sided concentric corrugations. The nano-lens, when illuminated with a radially polarized Laguerre-Gauss beam, focuses light in the far-field at distances equal 1 - 3 wavelengths depending upon wavelength and its geometry. Foci of diameter equal nearly 0.4 of a wavelength are achievable. The nano-lens acts like a classical optical high-numerical aperture system. Simulations using body-of-revolution finite-difference time-domain method illustrate the idea.