Unidirectional Extraordinary Sound Transmission with Mode-Selective Resonant Materials

Unidirectional wave propagation can introduce strong direction-dependent energy responses, and thus, greatly benefits the construction of switching and logic devices. Such an effect has drawn much attention in acoustics, but has not been able to practically address the essential issue of insufficient transmission efficiency in the forward direction. Here, we present a one-way structure that experimentally realizes near-total forward acoustic wave transportation, while still maintaining a broadband high contrast ratio and single-mode property. The experimentally observed rectification is achieved with a comprehensive design of combining acoustic wave intermode transitions, selective-mode filtering, and cavity resonance for strong wave-structure interactions. The demonstrated simplicity and flexibility make this material an appealing integration solution, enabling an alternative control methodology in biomedical ultrasonography, high-performance acoustic sensors, and noise control.