Cosine-type apodized spiral zone plate to handle the topological charge of a vortex beam

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.

Automated summary

By utilizing spiral petal-like zone plates, we have demonstrated that the geometric shape of a spiral element influences its charge. In order to control the topological charge of a vortex without changing its geometrical shape, we apodize a spiral zone plate with p spiral zones using a radial grating with spatial frequency m. Through experimentation, we find that the topological charge and handedness of the optical vortex depend on p and m.