Experimental study on vortex beam generation based on micron-scale all-optical magnetic holographic structures

In recent years, vortex beams carrying orbital angular momentum (OAM) have been widely applied to optical communications, optical manipulation, and precision measurement. However, traditional generation methods such as spiral phase plates, spatial light modulators, and metasurfaces, encounter several challenges, including structural rigidity, limited dynamic tunability, and inadequate integration capabilities. These limitations hinder the realization of reconfigurable and programmable vortex beam generation systems. In order to solve these problems, a novel vortex beam generation method based on all-optical magnetic holography is presented in this paper. In this technique, a single-pulse femtosecond laser is used in a dotted writing mode to engrave a pre-designed fork-shaped grating hologram onto the surface of a micron-scale magnetic material, GdFeCo. Under subsequent illumination with a plane wave, the vortex beam is reconstructed via the magneto-optical Faraday diffraction effect. Experimental results show that one-dimensional fork-shaped gratings can flexibly generate vortex beams with different topological charges (<i>l</i> = ±2, ±5, ±8), where the beam radius increases with the augment of topological charges. Furthermore, a two-dimensional fork-shaped grating, formed by superimposing horizontal and vertical one-dimensional gratings, can produce 3 × 3 vortex beam arrays with various topological charge distributions, enabling the spatial modulation of OAM. This method offers advantages such as reusability, long-term stability, and a compact structure, thus providing a programmable and reconfigurable platform for generating micro-structured vortex beams. Unlike traditional static optical elements, this approach enables dynamic, high-resolution, and easy-to-integrate solutions, and shows great application potential in OAM-based multi-channel optical communication, multi-particle manipulation, and parallel laser processing.