Spin-Orbit Angular Momentum Conversion in Coupled Nonparaxial Bessel Acoustic Vortices

Area of Science:

• Acoustics
• Wave Physics
• Nanotechnology

Background:

• Longitudinal acoustic waves possess both spin and orbital angular momentum (AM).
• Separating and measuring these AM components is challenging.
• Direct wave field measurements are difficult for studying both AM types.

Purpose of the Study:

• To theoretically explain and experimentally prove acoustic spin-orbit AM conversion.
• To develop a formulaic description for spin-orbit AM conversion in coupled Bessel acoustic vortices.
• To demonstrate contactless manipulation of micro-objects using this phenomenon.

Main Methods:

• Theoretical derivation of spin-orbit AM conversion in nonparaxial Bessel acoustic vortices.
• Experimental wave field measurements using passive artificial structures.
• Observation of Rayleigh particle rotation and circular translation.

Main Results:

• Successful theoretical explanation and experimental validation of acoustic spin-orbit AM conversion.
• Demonstration of conversion using passive artificial structures.
• Contactless, high-resolution manipulation of micro-objects, including controlled rotation and translation.

Conclusions:

• This work provides fundamental insights into the AM physics of classical waves.
• The demonstrated spin-orbit AM conversion has significant implications for acoustic sensing and imaging.
• Applications include advanced particle manipulation using acoustic radiation forces and torques.