Focusing Acoustic Beams with a Ball-Shaped Lens beyond the Diffraction Limit

The authors explore the concept of ``acoustic jets'' for the superfocusing of sound waves. Compared to conventional diffraction-limited systems, 50% better spatial resolution of ultrasound images can be achieved using a ball-shaped polymer lens. Excellent agreement is found between the experimental data and both analytical and numerical predictions. Potential applications extend beyond medical ultrasound to nondestructive testing, acoustic microscopy and sensing, microparticle manipulation, and sonar.