Efficient digital metasurfaces for full-space manipulation of acoustic waves with low crosstalk between reflection and transmission

Metasurfaces, as a class of emergent platforms, have shown enormous potentials in controlling classical waves. However, achieving simultaneous and dynamic manipulations of reflected and transmitted waves in a low-crosstalk and high-efficiency manner via a single metasurface still remains huge challenges in fact, especially for acoustic waves that lack of available vector degrees of freedom. Here, we propose and experimentally demonstrate an acoustic full-space digital metasurface consisting of arrays of dualchannel elements with variable coding states, and the reflected and transmitted sound waves can be controlled independently and dynamically. Benefitting from the dual-frequency design and the mode suppression effect, the presented element not only attains high efficiency (up to 80% in transmission mode, and nearly 100% in reflection mode), but also enables decoupled modulations of the reflection and transmission coefficients. To illustrate the presented acoustic metasurface, tunable beam deflection and alterable wave focusing are experimentally validated without inter-modal crosstalk on both sides of the platform, respectively. This work opens an avenue to control sound waves in multiple dimensions, which may further promote the development of miniaturized acoustic devices with high integration and versatility. CO 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).