We explore the spatial frequency property of the far-field diffraction intensity pattern of an optical vortex after passing through an annular aperture in detail. The result reveals that the spatial spectrum consists of alternate bright and dark rings and, in particular, the number of the bright rings is nicely identical to the absolute value of the topological charge. Based on this property, we present and demonstrate a simple technique to characterize the topological charge of an optical vortex through its diffraction intensity pattern after an annular aperture.
© 2009 Optical Society of America
Original Manuscript: September 15, 2009
Revised Manuscript: October 26, 2009
Manuscript Accepted: October 26, 2009
Published: November 24, 2009
Cheng-Shan Guo, Lei-Lei Lu, and Hui-Tian Wang, "Characterizing topological charge of optical vortices by using an annular aperture," Opt. Lett. 34, 3686-3688 (2009)