Acoustic Meta-lens: Computational Simulation and Underwater Experiments by a Three-dimensional Flat Acoustic Luneburg Lens

Based on the Luneburg lens refractive index formula, a three-dimensional flat-type acoustic Luneburg lens was designed to focus the incident wave on the opposite edge of the lens. The thickness of the three-dimensional spherical lens with a radius of 50 mm was reduced in half by compression in the x-axis direction. An elliptical meta-lens for underwater usage was fabricated by a metal 3D printer. Using the Acoustic Module of COMSOL Multiphysics, the focusing performance was studied by showing the sound pressure level around the lens at a frequency of 100 kHz. It has been found that the results of underwater experiments performed using a hydrophone, ultrasonic transducer, and LabVIEW-based measurement program are similar to those of computational simulations. These results show that it can be applied to ultrasonic sonar, gas leakage detection, and ultrasound imaging systems.