Broadband ultrasonic focusing based on circular Airy-like beam

¹ Jiangsu Key Laboratory of Opto- Electronic Technology, School of Physics and Technology, Nanjing Normal University Nanjing 210023, China
² Key Laboratory of Modern Acoustics of MOE, Department of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University - Nanjing 210093, China

^(a) E-mail: zhuxingfeng@njnu.edu.cn (corresponding author)
^(b) E-mail: wudajian@njnu.edu.cn
^(c) E-mail: liuxiaojun@nju.edu.cn

Received: 2 July 2022
Accepted: 12 December 2022

Abstract

Convergence of ultrasonic energy is of great importance in the medical and engineering fields. In this work, ultrasonic focusing based on circular Airy-like beam (CALB) is numerically and experimentally demonstrated. The CALB focusing can be achieved simply using a planar resin ring lens immersed in water. At 2 MHz, the acoustic intensity at the focus can reach 257 times that for the incident wave. Arising from the self-healing feature of Airy beams, the CALB focusing can be well maintained even if there exists an obstacle in the acoustic path. Meanwhile, the focusing behaviour is well performed in a broad frequency range of 1.5 MHz to 3.1 MHz due to the simple and non-resonant design. By adjusting the frequency of the incident waves, the focal length can be modified without changing the lens structure. The CALB focusing and the corresponding planar lens may promote wide applications in ultrasound imaging, non-destructive testing, acoustic tweezing and medical diagnostic techniques.