Remarkable ability of spiral orthogonal zone plate in generating various focused optical vortices

Abstract

We propose an amplitude spiral orthogonal zone plate (ASOZP) as a Cartesian-based spiral zone plate for generating variety of optical vortices. The presented model is made by overlapping closely a vertical spiral one-dimensional zone plate and a horizontal one. We demonstrate that the element produces diversity of focused vortices, in a way that the vorticity and number of the produced vortices could be easily manipulated. In addition, the generated vortices show rotation features in the vicinity of the focal plane. Furthermore, it is demonstrated that diffraction efficiency of the model is much more higher than the previously introduced Cartesian-based elements. We finally verify numerical results by experimental studies.