Orbital Angular Momentum Multiplexing in Space–Time Thermoacoustic Metasurfaces

Multiplexing technology with increased information capacity plays a crucial role in the realm of acoustic communication. Different quantities of sound waves, including time, frequency, amplitude, phase, and orbital angular momentum (OAM), have been independently introduced as the physical multiplexing approach to allow for enhanced communication densities. An acoustic metasurface is decorated with carbon nanotube patches, which when electrically pumped and set to rotate, functions as a hybrid mode‐frequency‐division multiplexer with synthetic dimensions. Based on this spatiotemporal modulation, a superposition of vortex beams with orthogonal OAMs and symmetric harmonics are both numerically and experimentally demonstrated. Also, flexible combinations of OAM modes with diverse frequency shifts are obtained by transforming the azimuthal phase distributions, which inspires a mode‐frequency‐division multiplexing approach that significantly promotes the communication capacity. Space–time thermoacoustic metasurface possess unusual capacities to simultaneously manipulate sound field distributions and harmonic frequency responses. Along this frontier, a mode‐frequency‐division multiplexing technique is established with a superposition of vortex beams carrying orthogonal orbital‐angular‐momentum modes at distinct frequency harmonics. The synthesized dimensionality introduces entirely new physics and design philosophies to multiplexing schemes, promising unprecedented functionalities in acoustic communication devices.