title: Highly focused spirally polarized beams.
abstract: The features of spirally polarized light beams focused by high-numerical-aperture systems are investigated in the nonparaxial regime by means of Debye theory with a multipole expansion technique. General expressions of the expanding coefficients are given, as well as the electric field distributions across the focal plane. Numerical examples are presented for the case of spirally polarized beams of the donut type. Comparisons with recent experimental results are also shown.
authors.affiliation: Istituto Nazionale per la Fisica della Materia, Dipartimento di Elettronica Applicata, Università Roma Tre Via della Vasca Navale, 84 I-00146 Rome, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Borghi
authors.forename: Massimo
authors.initials: M
authors.lastname: Santarsiero
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Alonso