Symmetry selective directionality in near-field acoustics

• 作者: Danmei Zhang Hao Ge Hong Chen Jie Ren Ming Bao Ming-Hui Lu Xiangyuan XU Yan-Feng Chen Yang Long
• 来源期刊: 国家科学评论（英文版）
• 关键词: acoustics near field symmetry
• 年，卷（期）: 2020,（6）
• 页码范围: 1024-1035
• 页数: 12页
• 语种: 英文
• DOI: 10.1093/nsr/nwaa040

摘要

Understanding unidirectional and topological wave phenomena requires the unveiling of intrinsic geometry and symmetry for wave dynamics.T-his is essential yet challenging for the flexible control of near-field evanescent waves,highly desirable in broad practical scenarios ranging from information communication to energy radiation.However,exploitations of near-field waves are limited by a lack of fundamental understanding about inherent near-field symmetry and directional coupling at sub-wavelengths,especially for longitudinal waves.Here,based on the acoustic wave platform,we show the efficient selective couplings enabled by near-field symmetry properties.Based on the inherent symmetry properties of three geometrically orthogonal vectors in near-field acoustics,we successfully realize acoustic Janus,Huygens,spin sources and quadrupole hybrid sources,respectively.Moreover,we experimentally demonstrate fertile symmetry selective directionality of those evanescent modes,supported by two opposite meta-surfaces.The symmetry properties of the near-field acoustic spin angular momenta are revealed by directly measuring local vectorial fields.Our findings advance the understanding of symmetries in near-field physics,supply feasible approaches for directional couplings,and pave the way for promising acoustic devices in the future.