Acoustic polygonal Bessel vortices based on metasurfaces

Acoustic vortices (AVs) play a significant role in the fields of acoustic communication and microparticle manipulation. Traditional AVs exhibit doughnut-shaped intensity profiles, which may restrict their application scenarios. Here, we propose an acoustic polygonal Bessel vortex (APBV), which can be generated by the coaxial coupling of multiple acoustic asymmetric Bessel vortices (AABVs). The number of sides of the APBV is dependent on the number of superimposed AABVs. Both topological charge and asymmetry coefficient of the AABV impact on the performance of the APBV, and the APBV also exhibits excellent nondiffracting characteristics. Moreover, an acoustic reflection metasurface (ARM) consisting of grooved units is designed to realize the APBV in air. Through simulations and experiments, we verify the generation of the APBV by the proposed ARM. The APBV may find potential applications in the polygonal manipulation of microparticles and acoustic communication.