title: 4Pi focusing of spatially modulated radially polarized vortex beams.
abstract: We propose a method for generating focal beams with special intensity distributions using radially polarized vortex beams in a 4Pi configuration. A spherical dark-hollow beam and hollow beam array can be obtained by vortex beams with topological charge of m=1. A dark channel can be generated using vortex beams with topological charge of m=2. The length of the well-defined hollow beam array and the dark channel is about 30λ. These interesting beams are useful in optical trapping and manipulation.
authors.affiliation: Department of Physics, Zhejiang University, Hangzhou 310027, China.
authors.forename: Ziyang
authors.initials: Z
authors.lastname: Chen
authors.forename: Daomu
authors.initials: D
authors.lastname: Zhao