Acoustic metasurfaces and topological phononics for acoustic/elastic device design

Abstract

This paper reviews recent progress in acoustic metasurface and a novel concept denoted as topological acoustic/phononics for designing compact yet efficient acoustic devices. After a brief review of these research area and their impact on ultrasonic technologies, I first introduce some of our efforts to develop highly efficient sound absorption devices using acoustic metasurface. A resonance-based mechanism to achieve efficient absorption in the metasurface structures thinner than wavelength of the incident sound is briefly discussed and its extensions to broad spectrum are highlighted. Next a valley topological phononic system is introduced and its applications to the design of phononic waveguide are exemplified. I show the band structure design for extracting topologically protected edge mode as well as the numerical and experimental demonstration of the robustness of phononic waveguides constructed in both acoustic and elastic regimes.

Valley edge states with opposite chirality in temperature dependent acoustic media

“…The field of acoustic topological QVHE is experiencing rapid advancement due to its adaptability and variety, offering a new avenue for manipulating the propagation of acoustic waves [23][24][25][26][27]. Numerous captivating subjects related to valley properties have been explored, such as topological oneway edge states [2,3,28], acoustic topological insulators [29,30], acoustic topological rainbow trapping [31,32] and topological valley transport [14,33,34].…”

Active control of localized mode and transmission in topological phononic waveguides by non-Hermitian modulation

“…30,31) Non-Hermitian modulated metamaterials exhibit asymmetric transmission and reflection scattering phenomena. [32][33][34] Moreover, the transmission of Z-shaped topological waveguides has been shown (experimentally) to be approximately 5% lower than that of a straight waveguide 35,36) Recently, such degradation of robustness in the presence of corners in waveguides has been quantitatively evaluated in terms of the "backscattering length" in valley photonic waveguides. [37][38][39] However, most of the previous efforts expended to improve transmission efficiency were devoted to the identification of ways to reduce the materials and/or structural losses effectively in waveguides.…”