Acoustic Waves Splitter Employing Orbital Angular Momentum

A sound splitter using the orbital angular momentum (OAM) of acoustic vortices is proposed and experimentally demonstrated. We show that a helical waveguide with a periodic array of shunted tubes can be used to achieve different transmission spectra for the acoustic vortices with opposite OAM topological charges due to their different Bragg scattering type bandgaps. By symmetry, the transmission spectra will reverse if the handedness of the helical waveguides is changed. Therefore, two such composite waveguides with opposite handedness can be combined to separate the OAM-dependent flow of sound. Our study of the acoustic vortex splitter may provide a route for demultiplexing in acoustic OAM-based communication.