No abstract

Higher-order exceptional points have attracted increased attention in recent years due to their enhanced sensitivity and distinct topological features. Here, we show that non-local acoustic metagratings enabling precise and simultaneous control over their multiple orders of diffraction can serve as a robust platform for investigating higher-order exceptional points in free space. The proposed metagratings, not only could advance the fundamental research of arbitrary order exceptional points, but could also empower unconventional free-space wave manipulation for applications related to sensing and extremely asymmetrical wave control.

Acoustic orbital angular momentum (OAM) has emerged as a new multiplexing degree of freedom in acoustic communication and shows application prospect in particle manipulation. The separation and detection of acoustic vortices carrying different OAM are significant in OAM-based signal de-multiplexing. In this work, we theoretically proposed and experimentally demonstrated an OAM prism for efficient and quantitative vortex perception, which converts the spiral vortices into the transmitted plane waves of different refraction angles. The refraction angle is linearly dependent on the topological charge of the vortices, enabling the expedient readout of the information coded in each vortex. The designed OAM prism provides a simple and effective method for vortex perception and on-chip detection in the transmission field.