Plasmonic focusing lens based on single-turn nano-pinholes array.

A miniature, simplified and planar plasmonic lens based on the circular array of nano-pinholes for on-axis beaming has been proposed and investigated systematically in the visible spectrum. Focusing properties of the designed plasmonic lens illuminated under circular polarized (CP) light for different radius of circular ring, filled with different dielectrics, with different numbers of pinholes have been investigated and analyzed in detail by finite element method (FEM). Our simulated results demonstrate such a miniature single-turn structure can also generate a totally centrosymmetric focusing spot under the CP illumination. Besides, by properly manipulating the filled dielectric and incident wavelengths, enhanced transmission, elongated depth of focus have also be realized, which can be used to modulate the transmitting fields effectively. Such a miniature and simplified plasmonic focusing lens can open up a vital path toward fiber-end planar photonic devices for biosensing and imaging.