Vol. 33, Issue 2-3, pp. 225-235 (2003)

Abstract

Fraunhofer diffraction patterns from a spiral phase element with an annular aperture are investigated, on normal incidence of a plane monochromatic wave, depending on a spiral distribution of the phase of a wave at the output from the element. Results of extensive numerical calculations are presented and analytical formulas are derived for a very thin aperture. Basic behaviour of diffraction patterns depending on the spiral’s slope is predictable from the analytical approximation.