Orbital Angular Momentum Multiplexing in Space-Time Thermoacoustic Metasurfaces

Area of Science:

• Acoustic communication
• Metasurface technology
• Information theory

Background:

• Multiplexing technology is vital for enhancing information capacity in acoustic communication.
• Existing methods use independent sound wave properties like time, frequency, amplitude, phase, and orbital angular momentum (OAM).
• There is a need for advanced multiplexing techniques to increase communication densities.

Purpose of the Study:

• To introduce a novel hybrid mode-frequency-division multiplexing approach for acoustic communication.
• To demonstrate the capability of an acoustic metasurface with carbon nanotube patches as a spatiotemporal modulator.
• To explore the flexible combination of OAM modes and frequency shifts for enhanced communication capacity.

Main Methods:

• An acoustic metasurface was engineered with electrically pumped, rotating carbon nanotube patches.
• Spatiotemporal modulation was utilized to create a hybrid mode-frequency-division multiplexer.
• Numerical simulations and experimental validations were performed to demonstrate the superposition of vortex beams and flexible OAM-frequency combinations.

Main Results:

• A superposition of vortex beams with orthogonal OAMs and symmetric harmonics was successfully demonstrated.
• Flexible combinations of OAM modes with diverse frequency shifts were achieved by manipulating azimuthal phase distributions.
• The proposed mode-frequency-division multiplexing approach significantly enhanced communication capacity.

Conclusions:

• The developed acoustic metasurface functions as an effective hybrid mode-frequency multiplexer.
• This technology offers a promising pathway for significantly increasing acoustic communication capacity.
• The findings inspire new strategies for advanced wireless communication systems.