Coherence combination to create a long depth bifocal diffractive lens capable of generating tailorable biannular and bottle beam

Abstract

Herein, the coherence combination is simply the sum of two or more diffractive elements to achieve a novel diffractive element with its unique behavior. Concerning this concept, we aim to demonstrate how a long-depth bifocal diffractive lens is emerged by a combination of two radial phase-shifted Fresnel zone plate. Besides, we will also show that the spacing between these foci is tailorable. Furthermore, it can be seen that this newly emerged element can turn out an incident plane beam to a biannular beam at a given distance whose radius changes as the spacing between the foci changes. Given these points, we demonstrate that a bottle beam is created whose length is also manageable. Finally, all simulation studies are followed by the corresponding experiments to verify them.