声学超构表面对声传播的调控机理及相关声学器件的实现

Acoustic metasurfaces, which are the low-dimensional version of bulk metamaterials, relax many of the limitations typically associated with bulk metamaterials such as complex structures, huge size, and high losses, so they are indicated as one of the most promising future directions in the field of acoustic artificial materials. As an ultrathin planarized version of metamaterials, metasurfaces are constructed by micro-structured elements with abrupt order, which can efficiently manipulate the amplitude and phase of acoustic waves. However, there are many limitations in the existing works, such as impedance mismatch, narrow operation band, monotonous control objects, and lack of studies on elastic waves. In this proposed project, we will make the theory analysis, computer simulation and experiments to give systematic and thorough research on acoustic metasurfaces. First, we will explore micro-structured elements with matched impedance which can be used to construct metasurfaces, and quantify the influence of the structural characters on the effective parameters. New physical mechanism and design method of broad-band metasurfaces will be explored and developed. The amplitude and phase of acoustic waves will be manipulated by the impedance and sound speed of metasurfaces, respectively. Furthermore, we will derive the generalized Snell’s law and design metasurfaces for elastic waves. Based on these foundations, we will develop new ultrathin acoustic functional devices according to the novel manipulation effects. This research will be helpful to discover new effects of acoustic waves and broaden the design concept of novel acoustic functional devices.

声学超构表面实现了体积型声学超构介质的低维化，克服了体积型超构介质结构复杂、体积大、损耗高等局限，已成为声学人工材料领域的重要研究方向。声学超构表面是由微结构单元按突变型宏观序排列形成的具有亚波长厚度的平面型超构介质，可灵活有效地调控声波的振幅、相位、传播模式等。针对现有声学超构表面存在的阻抗失配、工作频带窄、调控参数单一、缺乏弹性波超构表面等不足，本项目拟从理论分析、数值模拟和实验验证等不同方面，对声学超构表面进行系统深入的研究：（1）阐明微结构单元结构参数与有效声学参数之间的关系，构建阻抗匹配型超构表面；（2）研究宽带声学超构表面的工作机理，实现对声波的宽带调控；（3）利用超构表面内部有效声学参数分布实现对声波的振幅、相位及传播模式的调控；（4）推广弹性波广义Snell定律，实现超构表面对弹性波的有效调控。在此基础上，构建超薄声学器件。因此，本项目既富有学术价值，又具有重要的应用前景。

声学超构表面实现了体积型声学超构介质的低维化，克服了体积型超构介质结构复杂、体积大、损耗高等局限，已成为声学人工材料领域的重要研究方向。声学超构表面是由微结构单元按突变型宏观序排列形成的具有亚波长厚度的平面型超构介质，可灵活有效地调控声波的振幅、相位、传播模式等。近期研究表明，由于单元本身的复杂性，结构参数与调控性质的关系尚不清楚，基于相位延迟调制的负/零有效系数形成机理也未澄清。针对现有声学超构表面存在的阻抗失配、工作频带窄、调控参数单一、缺乏弹性波超构表面等不足，本项目从理论分析、数值模拟和实验验证等不同方面，对声学超构表面进行系统深入的研究。首先分析了单元的几何特征、排列方式等对等效参数的影响，构建了阻抗匹配型超构表面物理模型，取得的代表性成果包括提出了在无背景流速的超材料声子晶体中构造声学赝自旋偶极子和四极子模式、并实现声波拓扑传输的理论方法；进而对宽带声学超构表面的工作机理等关键问题进行了表征与设计，在此基础上，利用超构表面内部有效声学参数分布实现对声波的振幅、相位及传播模式的调控，构建了一系列声波功能器件，例如将声波类量子效应与声学新原理功能器件相结合，获得了拓扑保护声单向传输、可重构声学路径选择开关、声拓扑延迟线、声学定向天线等一系列新颖的声场调控功能；另外首次设计出基于近零系数超构表面的声波定向高灵敏度传感系统、数字编码超表面、全息超表面、非对称吸收超表面等一系列原型功能器件。本项目的研究成果发展了利用声学超构表面实现对声波传输、散射及折射等方面进行超常规人工调控的方法，在多种声学超构表面的设计、制备与相关新原理声学功能器件集成等方向取得了多项具有原创性的成果，不但丰富了声学学科的基础理论，还推动了声学功能器件技术的发展。项目支持下发表SCI论文49篇。其中以通讯作者发表PRL 2篇、AM 2篇（1篇封面）、PR系列5篇、APL 16篇（1篇封面，2篇亮点报道），他引1000余次，6篇入选ESI热点或高被引论文。