Axial Multifocus Beams Formed by Binary Optical Elements

Axial multifocus beams (AMBs) potentially offer convenience in scientific and industrial applications. However, the general approach used for forming AMBs based on the Fresnel zone plate limits the conceivable applications. In this paper, we introduce a custom-made method to generate AMBs by the point source method to obtain initial phase distribution and a modified Gerchberg–Saxton algorithm to iteratively optimize the phase distribution. Meanwhile, the sidelobe is also constrained in the design simultaneously. Here, foci numbers, positions, and intensity distributions of the AMBs have been designed by binary optical elements, which can be controlled readily and effectively. Both numerical simulations and experiment results show the validity of the proposed method.