Asymmetric Generation of Acoustic Vortex Using Dual-Layer Metasurfaces

In this Letter, we introduce a new paradigm for achieving robust asymmetric generation of acoustic vortex field through dual-layer metasurfaces by controlling their intrinsic topologic charges and the parity of geometry design. The underlying physics is contributed to the one-way process of orbital angular momentum (OAM) transition ensured by the broken spatial symmetry and the external topologic charge from the vortex diffraction. We further experimentally demonstrate this novel phenomenon. Our findings could provide new routes to manipulate the asymmetric response of vortex fields, including one-way excitation and propagation, and promise potential applications in passive OAM-based diodes.

Automated summary

In this study, a new method for achieving robust asymmetric generation of acoustic vortex field through dual-layer metasurfaces is introduced. This is achieved by controlling the intrinsic topologic charges and the parity of geometry design. The underlying physics is contributed to the one-way process of orbital angular momentum transition ensured by the broken spatial symmetry and the external topologic charge from the vortex diffraction. The novel phenomenon is experimentally demonstrated, providing new routes to manipulate the asymmetric response of vortex fields and potential applications in passive OAM-based diodes.