Broadband Acoustic Collimation and Focusing using Reduced Aberration Acoustic Luneburg Lens

TL;DR

This paper introduces a practical, broadband, and omnidirectional acoustic Luneburg lens with reduced aberrations, demonstrated through simulation and experimental testing of 2D and 3D models, improving acoustic wave collimation and focusing.

Contribution

The paper presents the first realization, simulation, and experimental validation of a 3D reduced aberration acoustic Luneburg lens for broadband and omnidirectional applications.

Findings

RAALL achieves better focusing than traditional lenses.

The 2D and 3D models demonstrate broadband and omnidirectional performance.

Experimental results confirm theoretical and numerical predictions.

Abstract

Acoustic Luneburg lens is a symmetric gradient-index lens with a refractive index decreasing radially from the centre to the outer surface. It can be used to manipulate acoustic wave propagation with collimation and focusing capabilities. However, previously studied acoustic Luneburg lens works only at audible frequency ranges from 1 kHz to 7 kHz, or at a single ultrasonic frequency of 40 kHz. In addition, the acoustic Luneburg lens at high frequency is not omnidirectional in the previous researches. Furthermore, there is no realization of simulation and experimental testing of 3D acoustic Luneburg lens until now. In this paper, a practical reduced aberration acoustic Luneburg lens (RAALL) are proposed for broadband and omnidirectional acoustic collimation and focusing with reduced aberrations. Ray tracing technique shows that RAALL can achieve a better acoustic focusing compared with traditional modified acoustic Luneburg lens. Following that, two models of RAALL are designed and fabricated through additive manufacturing technology: a 2D version and a 3D version. Collimation and focusing performances of the ultrasonic waves are theoretically, numerically and experimentally demonstrated for both 2D and 3D lenses, and their broadband and omnidirectional characteristics are verified.