Acoustic metasurfaces and topological phononics for acoustic/elastic device design

Abstract

Abstract This paper reviews recent progress in acoustic metasurfaces and the novel concept of “topological acoustic/phononics” for designing compact yet efficient acoustic devices. After a brief review of this research area and its impact on ultrasonic technologies, some of the efforts to develop highly efficient sound absorption devices using acoustic metasurfaces are introduced. A resonance-based mechanism to achieve efficient absorption in metasurface structures thinner than the wavelength of the incident sound is briefly discussed, and its extensions to a broad spectrum are highlighted. Next, a valley topological phononic system is introduced, and its applications to the design of phononic waveguides are exemplified. The band structure design for extracting topologically protected edge modes is shown together with a numerical and experimental demonstration of the robustness of phononic waveguides constructed in both acoustic and elastic regimes.