The generation of acoustic multi-vortex beams using a phase-only holographic lens

The generation of acoustic vortex beams has garnered significant research interest in recent years due to their diverse applications, including acoustic communication, particle manipulation, and biomedical ultrasound. However, incorporating more vortices and expanding the capacity of these beams and related devices in three dimensions remain challenging. In this study, we propose a phase-constrained iterative angular spectrum method for fabricating a 3D-printed holographic lens capable of reconstructing multi-vortex acoustic beams within a 3D volume. To evaluate the performance of the proposed lens, we conduct tests using both numerical simulations and practical underwater measurements. Furthermore, we demonstrate the transfer of acoustic angular momentum to two absorbent acoustic objects, achieving rotation of these objects with the performance influenced by vortices at target positions. The results indicate that the proposed method can generate multiple acoustic vortex beams within a 3D volume. This capability enhances the effectiveness and versatility of various applications, such as the manipulation of three-dimensional objects and high-density information transmission.