title: Demonstration of flat-top focusing under radial polarization illumination.
abstract: We experimentally demonstrate the generation of a flat-top intensity distribution using a radially polarized vector beam. Our approach uses higher numerical aperture focusing than what has been previously reported for a single, fixed, vector beam. In addition, the flat-top focus generated in our scheme exhibits a polarization gradient along the radial coordinate in the focal volume, with an on-axis longitudinal field component that persists over 2λ, which is a stark difference from conventional flat-top fields, which exhibit intensity profiles that are uniformly polarized. Our experimental results are found to be in good agreement with the theoretical prediction.
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.forename: Santosh
authors.initials: S
authors.lastname: Tripathi
authors.forename: Kimani C
authors.initials: KC
authors.lastname: Toussaint