Generation of topologically diverse acoustic vortex beams with same divergence angle using discrete active helical arrays

In the process of multiplexing acoustic orbital angular momentum to realize underwater acoustic communication, the demodulation process is always affected by the larger divergence angle of higher-order acoustic vortex beams. To restrain the influences of this problem, proposed here are discrete active helical arrays with different heights and radii to generate topologically diverse underwater acoustic vortex beams, and the reasons for the different divergence angles of acoustic vortex beams with different orders are analyzed. In finite-element analysis and experiments, the same divergence angle of acoustic vortex beams with different orders is obtained, and an effective method is provided for emitting underwater acoustic vortex beams. The proposed design has potential applications in underwater acoustic communication.