Observation of higher-order exceptional points in a non-local acoustic metagrating

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. Exceptional points are singularities in the parameter space of a physical system where two or more eigenvalues, and their associated eigenvectors, simultaneously coalesce. Here, it is shown that non-local acoustic metagratings that enable precise control over their multiple orders of diffraction, can serve as a robust platform for investigating higher-order exceptional points in free space.