Acoustic transverse vortex synthesis with arbitrary topological charge using metasurfaces

Theoretical research on acoustic vortex fields holds significant guiding importance for the design and application of novel vortex-based functional devices. However, the synthesis mechanism of two-dimensional vortex fields carrying arbitrary orbital angular momentum (OAM) remains an unsolved scientific challenge. In this paper, we propose and demonstrate an innovative approach based on the collaborative manipulation of acoustic metasurfaces (AMs), which establishes a universal theoretical framework for the synthesis mechanism of arbitrary vortex fields by reshaping the field distributions of different vortex sources. The essence of this synthesis process is to achieve the secondary reconstruction and energy redistribution of vortex fields through the directional phase compensation and the precise control of material parameters. Numerical demonstrations and the designed acoustic microstructure simulations confirm the synthesizing phenomenon of vortex waves using multiple AMs under the cases of both the same and different OAMs. This work is expected to provide the direct theoretical support for compact vortex-based devices and novel vortex functional devices.