Three-dimensional omnidirectional acoustic orbital angular momentum emitter with tunable focus

Area of Science:

• Acoustics
• Wave physics
• Optical engineering

Background:

• Acoustic vortex (AV) beams, utilizing orbital angular momentum (OAM), offer enhanced communication capacity and acoustic field engineering capabilities.
• Developing high-intensity, low-sidelobe, and highly directional AV beams is crucial for advancing OAM-based acoustic technologies.
• Traditional methods often involve high costs due to extensive use of active components.

Purpose of the Study:

• To propose a novel approach for generating focused acoustic vortex (FAV) beams with tunable properties.
• To address the limitations of existing methods, particularly high costs and fabrication complexity.
• To enable flexible control over FAV beam characteristics, including focal point position and topological charge.

Main Methods:

• Utilized a simplified sectorial transducer array coupled with multiple cascaded discrete acoustic lenses (DALs).
• DALs with designated phase modulation profiles were sequentially placed before the transducer.
• Tuning DAL orientation angles allowed for 3D focal point translation, while adjusting transducer sector phase delays enabled topological charge switching.

Main Results:

• Successfully generated focused acoustic vortex (FAV) beams by phase modulation of AV beams emitted by the transducer array.
• Demonstrated free translation of the focal point within full 3D space by adjusting DAL orientation angles.
• Achieved switching of the topological charge of FAV beams during focal point movement by adjusting transducer sector phase delays.

Conclusions:

• The proposed approach offers a cost-effective and simplified method for fabricating passive devices for advanced acoustic applications.
• This technique provides precise control over FAV beam characteristics, enabling versatile applications.
• The method holds significant potential for particle manipulation and acoustic communication technologies.