Generation of acoustic self-bending and bottle beams by phase engineering

• Published in: Nature communications Vol. 5; no. 1; p. 4316
• Main Authors: Zhang, Peng, Li, Tongcang, Zhu, Jie, Zhu, Xuefeng, Yang, Sui, Wang, Yuan, Yin, Xiaobo, Zhang, Xiang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03-07-2014; Nature Publishing Group
• Subjects: 639/301/357/1015; 639/766/25/3927; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms5316

Directing acoustic waves along curved paths is critical for applications such as ultrasound imaging, surgery and acoustic cloaking. Metamaterials can direct waves by spatially varying the material properties through which the wave propagates. However, this approach is not always feasible, particularly for acoustic applications. Here we demonstrate the generation of acoustic bottle beams in homogeneous space without using metamaterials. Instead, the sound energy flows through a three-dimensional curved shell in air leaving a close-to-zero pressure region in the middle, exhibiting the capability of circumventing obstacles. By designing the initial phase, we develop a general recipe for creating self-bending wave packets, which can set acoustic beams propagating along arbitrary prescribed convex trajectories. The measured acoustic pulling force experienced by a rigid ball placed inside such a beam confirms the pressure field of the bottle. The demonstrated acoustic bottle and self-bending beams have potential applications in medical ultrasound imaging, therapeutic ultrasound, as well as acoustic levitations and isolations.
Acoustic metamaterials provide tailored beams for a range of purposes, but are limited to environments where the material structures can be deployed. By careful choice of phases for a speaker array, Zhang
et al
. show that bottle or bent beams can be created in air, without the use of metamaterials.