title: Characterization of vector diffraction-free beams.
abstract: It is observed that a constant unit vector denoted by I is needed to characterize a complete orthonormal set of vector diffraction-free beams. The previously found diffraction-free beams are shown to be included as special cases. The I-dependence of the longitudinal component of diffraction-free beams is also discussed.
authors.affiliation: Department of Physics, Shanghai University, Shanghai 200444, China.
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Wang
authors.forename: Shuang-Yan
authors.initials: SY
authors.lastname: Yang
authors.forename: Chun-Fang
authors.initials: CF
authors.lastname: Li