Experimental demonstration of extremely asymmetric flexural wave absorption at the exceptional point

Recently, non-Hermitian systems have attracted great attention on wave manipulations due to the extraordinary wave control abilities by introducing lossy or active elements. One of the exotic behaviors that could be achieved in such non-Hermitian systems is unidirectional zero reflection, which occurs at the so-called exceptional points. In this letter, we design and experimentally demonstrate extremely asymmetric flexural wave near-unit absorption and unidirectional zero reflection at the exceptional point with a metalayer composed of a pair of loss-induced asymmetrical resonators. The mechanism behind such extremely asymmetric behaviors is explored. Also, we find that the exceptional point and critical coupling condition are simultaneously fulfilled by the metalayer. Numerical and experimental results are compared, and a good agreement is found. A design of broadband absorption is further suggested and validated through numerical simulation in the end. The results shown in this work not only provide a fundamental understanding of asymmetric flexural wave absorption in the transmission problem, but also offer a remarkable way to tailor flexural wave propagation. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

This letter presents the design and experimental demonstration of extremely asymmetric flexural wave near-unit absorption and unidirectional zero reflection at the exceptional point using a metalayer composed of a pair of loss-induced asymmetrical resonators. The mechanism behind such extremely asymmetric behaviors is explored, and it is found that the exceptional point and critical coupling condition are simultaneously fulfilled by the metalayer. A design of broadband absorption is further suggested and validated through numerical simulation.