Mixed focused-acoustic-vortices generated by an artificial structure plate engraved with discrete rectangular holes

Recently, considerable attention has been paid to acoustic vortices (AVs) due to their increasing demands for practical applications. Conventional AV generators usually realize the AV with only one topological charge (TC), namely, carrying one orbital angular momentum. In this work, we demonstrate that mixed focused acoustic vortices (FAVs) with two TCs can be achieved via an artificial structure plate engraved with discrete rectangular holes (ASP-RHs). It is found that the performance of the mixed FAVs is highly dependent on the degeneracy of the ASP-RH. By modulating the number and distribution of RHs on the ASP, the mixed FAVs with different TCs can be generated. Finally, we experimentally confirm the generation of the mixed FAVs by the well-designed ASP-RH. The mixed FAVs may provide more opportunities for applications in particle manipulation and acoustic communication.