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A plasmonic nanolens with metallic nano-slits thin film

Metallic nano-slits film is proposed to implement beam manipulation, such as focusing, deflecting and imaging etc. The principle of this novel nano metric device, termed as plasmonic nano lens, is based on the different phase retardation of light when transmitted through a metallic film with arrayed nano-slits, which have constant depth but variant widths. The slits transport electro-magnetic energy in the form of surface plasmon polaritons (SPPs) in nanometric waveguides and provide desired phase retardations of beam manipulating with variant phase propagation constant. Numerical simulations of illustrative examples are performed through finite-difference time-domain (FDTD) method and show its validity as a lens and other potential photonic devices. In addition, extraordinary optical transmission of SPPs through sub-wavelength metallic slits is observed in the simulation and implies higher efficiency than usual binary devices featured with transparent and opaque regions.