title: Nanofocusing on circularly distributed tapered metallic waveguides by means of plasmonic vortex lenses.
abstract: We report our experimental results on the nanofocusing effect at the apex of planar nanotips placed at the center of a plasmonic vortex lens (PVL). PVLs are helical gratings that are able to generate surface plasmon polaritons (SPPs) carrying orbital angular momentum. A specific design allows us to couple the PVL with nanostructures placed at its center. The proposed configuration allows a simultaneous nanofocusing effect on four facing planar nanotips, showing efficient condensation of SPPs at the metal-air interface toward the end point of the tips. An optimized fabrication process allows us to prepare high-quality structures with a sharp tip apex. Near-field scanning optical microscopy has been used to demonstrate the nanofocusing effect.
authors.forename: D
authors.initials: D
authors.lastname: Garoli
authors.forename: T
authors.initials: T
authors.lastname: Ongarello
authors.forename: P
authors.initials: P
authors.lastname: Zilio
authors.forename: M
authors.initials: M
authors.lastname: Carli
authors.forename: F
authors.initials: F
authors.lastname: Romanato