Asymmetric generation of broadband beam splitting using a dissipative acoustic coupler-based metamaterial

In this work, a broadband acoustic beam splitter that has an asymmetric transmission feature is proposed by constructing a dissipative acoustic coupler. The beam splitter has a simple configuration, requiring only three straight air cavities and two space-independent air slits. The dissipation just needs to be uniformly exerted into the middle cavity, and thus the complicated modulation of the loss factor is avoided. The acoustic waves incident from one-side of a certain cavity exhibit an equal-weighted intensity distribution along top and bottom cavities, while those cannot transfer back to a certain cavity when top and bottom cavities incident from the other side simultaneously. Given the excellent asymmetric wave propagating performance, a one-way acoustic mode converter is further constructed by sealing both sides of the middle cavity. The 0-order acoustic waves can be converted into 1-order acoustic waves unidirectionally in a broadband from 3.8 kHz to 10 kHz. More uniquely, an acoustic metamaterial that has an ability of asymmetric transmission is designed as well by adopting the mode converters as basic meta-atoms, through which the incident waves can split into two parts with opposite directions unidirectionally. By taking advantage of the broadband feature of the metamaterial, the angle of the splitting beam is able to be manipulated flexibly. Our work provides an effective solution for the realization of asymmetric and broadband beam splitting, which may have potential applications in numerous fields such as acoustic detection and acoustic logic operations.