Tunable Asymmetric Transmission via Lossy Acoustic Metasurfaces

Abstract

In this study, we show that robust and tunable acoustic asymmetric transmission can be achieved through gradient-index metasurfaces by harnessing judiciously tailored losses. We theoretically prove that the asymmetric wave behavior stems from loss-induced suppression of high order diffraction. We further experimentally demonstrate this novel phenomenon. Our findings could provide new routes to broaden applications for lossy acoustic metamaterials and metasurfaces.

Robust 2D/3D multi-polar acoustic metamaterials with broadband double negativity

“…During the past two decades, choreographed artificial metamaterials [1][2][3] have been explored to manipulate electromagnetic [1], acoustic [2,4] and elastic [5][6][7] wave propagations. Acoustic metamaterials (AMMs) can lead to diverse subwavelength functionalities [8], such as perfect absorption [9][10], negative refraction [11][12][13][14], phase modulation [15][16][17][18][19][20][21], etc., showing promise for applications in sound reconstruction [22], imaging [13-14, 18, 21, 23-24], energy harvesting [25][26] and cloaking [27][28], etc. Since double negativity is a cornerstone in many applications such as the super-resolution medical ultrasonic imaging, double-negative AMMs have been drawing persistent attention and have been synthesized through various means such as coupled Helmholtz resonators [29], membranes [30], combined membranes and Helmholtz resonators [31], space-coiling units [11][12] and macroporous silicone rubber microbeads [31].…”

Acoustic resonance coupling for directional wave control: from angle-dependent absorption to asymmetric transmission

“…Interaction between resonators with a large loss contrast has drawn attention, because it is often avoidable and, more importantly, functions as an essential building block of non-Hermitian metamaterials, such as a lossy acoustic metasurface [16,17], a lossy acoustic topological insulator [18] and a passive PT symmetry structure [19]. To study coupled resonance in optics, couple-mode theory has proven useful for understanding the interaction between resonance modes [20,21].…”

Improving directional radiation quality based on a gradient amplitude acoustic leaky wave antenna

“…accurate phase response of the metasurface and explore the fascinating wavefront phenomena. By using an acoustic metasurface with gradient phase profile, various unique properties have been demonstrated, such as anomalous refraction/reflection [17][18][19], flat focusing [20,21], asymmetric propagation [22,23], wave bending [24,25] and propagation waves being converting into surface waves [26]. In addition to metasurface with gradient phase, another metasurface with gradient amplitude has recently been developed for the complete control of acoustic waves [27].…”