Grating- and checkerboard-based zone plates as an optical array generator with a favorable beam shape.

Abstract

The combination of a grating as a periodic object and a Fresnel zone plate with a quasi-periodic structure leads us to propose some novel array generator elements. It is shown that diffraction performance of the proposed element depends on the grating structure, so that the diffraction performance may efficiently be increased if the grating is replaced with a checkerboard structure. Depending on the kind of zone plate, we have demonstrated that the corresponding array generator is also created. For instance, a focused array of vortices is generated when the zone plate is replaced with a spiral zone plate. We have also clarified that the method allows us to generalize it to the other class of the zone plate-based elements, e.g., a cross zone plate. Namely, when the cross zone plate is used instead of the Fresnel zone plate, a spot array generator is again created whose diffractive performance is improved by modifying its phase structure. Also, it is clearly shown that the focusing feature of the element depends on the grating period. Finally, there is a good agreement between the simulation results and the corresponding experimental works.