Broadband acoustic focusing by symmetric Airy beams with phased arrays comprised of different numbers of cavity structures**Project supported by the National Natural Science Foundation of China (Grant Nos. 11774137 and 11404147), the Major Program of the National Natural Science Foundation of China (Grant No. 51239005), the Natural Science Foundation of Jiangsu Province, China (Grant Nos. BK20140519 and BK20140523), the Jiangsu

Abstract

We realize broadband acoustic focusing effect by employing two symmetric Airy beams generated from phased arrays, in which the units of the phased arrays consist of different numbers of cavity structures, each of which is composed of a square cavity and two inclined channels in air. The exotic phenomenon arises from the energy overlapping of the two symmetric Airy beams. Besides, we demonstrate the focusing performance with high self-healing property, and discuss the effects of structure parameters on focusing performance, and present the characteristics of the cavity structure with straight channels. Compared with other acoustic lenses, the proposed acoustic lens has advantages of broad bandwidth (about 1.4 kHz), high self-healing property of focusing performance, and free adjustment of focal length. Our finding should have great potential applications in ultrasound imaging and medical diagnosis.