利用亚波长声人工结构控制声波单向传播的理论与实验研究

近年来，声单向传播的研究以其丰富的物理内涵和潜在的应用前景受到了广泛关注。由于缺乏实现亚波长结构的声单向传播机制，已有的被动式声单向传播结构的尺远大于入射声波波长，限制其低频应用。本项目以申请人近年来有关声子晶体和声单向传播的工作为基础，利用具有特殊低频禁带效应的一维流/固型Bragg声子晶体和具有低频衍射效应的一维周期性声栅构造亚波长声人工结构，实现声波的单向传播的有效控制。一方面，通过研究声子晶体低频禁带产生的物理过程、带隙特征及带隙调节规律等，构造较宽且可调谐的低频禁带，建立声波高效反向截止的调控机制；另一方面，研究声栅结构的低频衍射特性，优化衍射结构，建立声波正向导通透射增强的调控机制。此外，还将开展实验研究，对理论研究成果进行实验验证。本项目的顺利开展有望突破被动式声单向传播设计中面临的“波长-尺寸”限制问题，有助于声二极管等声整流器件朝着小型化和集成化方向发展。

One-way transmission devices that allow acoustic waves to propagate only along one direction have received significant attention because of the rich physics and many potential applications. However, most proposed designs, such as acoustic superlattices and nonlinear acoustic diodes, are much larger than the wavelength, which are impractical for aqueous applications that require unidirectionality at low frequencies. For practical applications, miniaturization and low energy consumption are the inevitable developing trend of acoustic devices. In this work, subwavelength acoustic one-way transmission will be realized based on low-frequency forbidden transmission of one-dimensional solid-fluid acoustic superlattices. Our design is comprised of a 1-D superlattice, serving as a low-frequency forbidden transmitter, and a periodic rectangular grating serving as the wave-front converter. The rectifying mechanism of the subwavelength one-way structure will be carefully analyzed theoretically. Full-wave simulations will be performed to derive the transmission ratios over a broadband of frequencies. Finally, the performance of the proposed one-way model will be verified experimentally. This novel design will break the size-wavelength limitation to allow unidirectional low frequency acoustic wave transmissions, which is desirable for the miniaturization of integrated acoustic devices in unidirectional signal transmission applications.