Herein, we present a so-called multiregion spiral square zone plate (MRSSZP), in which a spiral square zone plate is divided into a few regions, so that every region is composed of Fresnel zones, and the first zone of a given region is the same as the last zone of the previous region from a transmission point of view. We show that an MRSSZP can generate unique features of an array of an optical vortex with topological charge ±1, so that the number of vortices is directly related to the number of regions. We also demonstrate that, for an MRSSZP with topological charge 2, an array of dark cores is formed, which have phase structures similar to that of the interference of optical vortices with opposite topological charges. Besides, the focused vortex array follows a modulo-4 transmutation rule. In addition, when the topological charge becomes multiples of 4, an array of focal bright spots surrounded by a dark ring is generated. Numerical and experimental results verify the superior features of an MRSSZP.
By taking advantage of spiral petal-like zone plates, we have recently demonstrated that a spiral element's geometric shape impacts its charge. Keeping it in mind, we aim to control the topological charge of a vortex using phase modification of a spiral zone plate without transforming its geometrical shape. This is achieved by apodizing a spiral zone plate having p spiral zones with a radial grating with spatial frequency m. Having implemented some gratings with different m, we realized that an optical vortex is produced whose topological charge and its handedness depend on p and m. Consequently, a constant phase replaces on-axis screw dislocation under the situation that p takes odd multiples of m. Studies are carried out for large and small pairs of (p, m) and various gaps between the couple.
By taking advantage of spiral petal-like zone plates, we have recently demonstrated that a spiral element's geometric shape impacts its charge. Keeping it in mind, we aim to control topological charge of a vortex by means of phase modification of an spiral zone plate without transforming its geometrical shape. This is achieved by apodizing a spiral zone plate having p spiral zones with a radial grating with spatial frequency m. Having implemented some radial gratings with different m, we realized that an optical vortex is produced whose topological charge and its handedness are dependent on p and m. Consequently, a constant phase replaces on-axis screw dislocation under the situation that p takes an odd multiples of m. Studies are carried out for both large and small pairs of (p,m) and various gaps between the couple.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.