平面宽带非对称传播声学器件的研究与应用

The realization of acoustic one-way transmission breaks through the fundamental barrier in conventional acoustics theory, with great potential to revolutionize the existing acoustic techniques. The past few years have witnessed growing interests dedicated to the researches on one-way manipulation over acoustic waves from both the acoustic and physics communities. Yet the design and fabrication of planar acoustic devices with broadband asymmetric transmission still remains challenging despite their pivotal significance for diverse applications. The applicant has studied acoustic one-way manipulation both theoretically and experimentally, by proposing to use natural materials to construct a simple structure capable of producing asymmetric transmission in broad band and realizing active-element-based nonreciprocal acoustic devices with invariant working frequency. The current project aims at investigate the design and fabrication of broadband planar acoustic one-way devices and their practical application. The major contents of this project include: 1) Proposal of new mechanisms for designing planar devices with broadband functionality via introduction of physical effects like phase gradient modulation; 2) Development of designing theory of active devices capable of producing real-time one-way control based on coupling effects between acoustic wave and electric and magnetic fields; 3) Design and fabrication of planar devices featured with negligible dispersion, low loss and reconfigurability by combining the advantages of active elements and passive materials, and optimization of their system parameters. Based on this, we will further explore the possibility of finding the real-world application of such conceptual devices in various fields such as noise control and medical ultrasound diagnosis and treatments.

声单向传播的实现突破了经典声学理论局限，并有望带来声学技术的革新，近年来得到了国内外学术界的广泛关注。可实现宽带非对称声波操控的平面器件具有重要的应用价值，但其设计与制备仍是具有挑战性的难题。申请人已开展了对声单向操控的理论与实验研究，提出了利用天然材料构建的简单结构产生宽带非对称传播的物理机制，并基于有源器件设计制备了可保持频率不变的非互易声学器件。本项目拟基于原有研究优势，深入研究宽带平面声单向器件的设计原理、制备方法及应用方法。主要研究内容包括：1) 对天然材料构建的单向体系引入相位梯度操控等机制，发展宽带器件平面化的新原理；2) 引入声与电、磁等能量形式的耦合效应，提出可实时单向操控的器件设计理论；3) 结合有源器件与无源材料优势，设计与制备具有非色散、低损耗及可控性等重要性质的平面器件，并对其参数进行优化设计。基于此，探索将此类新概念器件在噪声控制、医学超声等重要领域的实际应用。

项目研究基于原有的工作基础，围绕原计划中提出的关键科学问题及相关研究领域的前沿问题，深入系统地研究了复杂声学系统中的非对称声传播效应，完成了预定的研究目标。基于此，面向与声学探测、通信等方面国家重大需求密切相关的声准直调控问题，对原有的声单向操控研究方向进行拓展，并结合声学超构材料新颖的声学性质，在声准直调控研究领域中也取得了若干重要研究成果。主要研究成果包括：1) 提出了多种声单向操控的新机制，发展了流体连通型和相位梯度型非对称声学器件的设计理论，可通流体的非对称声传输结构具有高效、工作带宽超宽以及不影响声、光及其他流体流通等优点；基于相位梯度的非对称声传输器件具有平面化、易于调控等优点。上述非对称声传输理论的提出有效改善了声单向器件的性能并拓展了其应用场景，为此类器件存在的效率低下、带宽受限及路径阻塞等问题提供了解决方案，对于噪声控制及医学诊疗等重要领域具有重要意义。此外，结合有源器件与无源材料优势，将相位梯度结构和有源电路结合，实现了对声波输出角度的可编程实时调控。2) 建立了利用超薄声人工结构对声波实现准直操控的理论方法, 利用中心折叠狭缝处Fabry-Perot 共振和两侧类HR 共振的耦合，以深亚波长尺度的器件产生了传输距离超过125个波长的高效准直声束，有望在声学检测、水下通信及对抗等重要场合产生广泛应用。