Transmission-Reflection-Integrated Multifunctional Continuously Tunable Metasurfaces for Decoupled Modulation of Acoustic Waves

The effective modulation of acoustic fields is the most important property of acoustic metasurfaces. The realization of full-space wavefront control can significantly enhance the functionality of metasurfaces; however, the existing solutions to this problem are limited by the coupled modulations of the transmitted and reflected wavefronts. In this study, we demonstrate the possibility of controlling transmitted and reflected acoustic wavefronts in a decoupled manner with a passive structure. Simulated analyses of the parameter dependences of the transmission and reflection phases reveal that these phases can be combined arbitrarily within a range of structural parameters. Meanwhile, tunable designs increase the flexibility and simplicity of the modulation of acoustic waves. Using such a tunable structure, a transmission-reflection-integrated (TRI) metasurface is designed. By applying a single TRI metasurface, multiple independent functions are simultaneously realized in the transmitted and reflected regions, which is further confirmed by pancratic multifocal focusing (performed both experimentally and theoretically) and holographic imaging simulations. The simulated, calculated, and experimental data obtained demonstrate efficient wavefront control and excellent functional-integration performance of the TRI metasurface. In this paper, we propose a decoupled method for the simultaneous manipulation of reflected and transmitted acoustic waves, which can enhance the spatial utilization and functionality of acoustic devices.