Three-dimensional acoustic lensing with a bubbly diamond metamaterial

TL;DR

This paper demonstrates that a diamond-structured bubbly metamaterial can act as a three-dimensional acoustic lens with super-resolution capabilities, enabling advanced 3D imaging and focusing in water.

Contribution

It introduces a novel bubbly diamond metamaterial with negative refractive index properties for 3D acoustic lensing and super-resolution imaging.

Findings

Achieves negative index of -1 at specific frequency

Demonstrates super-resolution focusing in near field

Designs a 3D flat acoustic lens

Abstract

A sound wave travelling in water is scattered by a periodic assembly of air bubbles. The local structure matters even in the low frequency regime. If the bubbles are arranged in a face-centered cubic (fcc) lattice, a total band gap opens near the Minnaert resonance frequency. If they are arranged in the diamond structure, which one obtains by simply adding a second bubble to the unit cell, one finds an additional branch with a negative slope (optical branch). For a single specific frequency, the medium behaves as if its refractive index (relative to water) is exactly $n=-1$. We show that a slab of this material can be used to design a three three-dimensional flat lens. We also report super-resolution focusing in the near field of the slab and illustrate its potential for imaging in three dimensions.