title: Phase singularities of the longitudinal field components in the focal region of a high-aperture optical system.
abstract: We study the behavior of the longitudinal components of strongly focused electromagnetic fields. These components possess phase singularities and phase saddles that can be annihilated when the aperture angle of the lens is changed.
authors.affiliation: Department of Physics and Astronomy, Free University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
authors.forename: Damon W
authors.initials: DW
authors.lastname: Diehl
authors.forename: Taco D
authors.initials: TD
authors.lastname: Visser