Generation of tunable broadband acoustic vortex via reconfigurable multilayered metasurface

Acoustic metasurface-based vortex generators have shown effective feasibility, yet they remain constrained by limited bandwidth or fixed functionality. Here, we propose a reconfigurable multilayered (RM) metasurface capable of dynamically manipulating acoustic vortices over a broadband frequency range. The RM metasurface comprises eight sector-shaped units and is placed into a circular waveguide supporting a maximum topological charge of lM = 1. Each sector-shaped unit is built upon the designed coiling structure and consists of two auxiliary layers and one functional layer with rotatable blades. Dynamic reconfiguration of the intrinsic topological charge (lξ) in RM metasurface is achieved by rotating the blades in the functional layer of each sector-shaped unit. Simulation results confirm that across the frequency range of 3.1–3.9 kHz, the tunable lξ enables the conversion of an incident acoustic plane wave into multiple acoustic vortex states. This work balances the broadband operation and tunable functionality in acoustic vortex generation, providing a promising platform for practical acoustic vortex-based applications.