Experimental Demonstration of the Non‐Hermitian Radio Frequency Metasurface with Polarization‐Dependent Unidirectional Reflectionless Propagation

Abstract

Unidirectional reflectionlessness is one of the most fascinating effects at the exceptional point (EP) in a non‐Hermitian system. Herein, a polarization‐dependent non‐Hermitian radio frequency metasurface with unidirectional reflectionless (UR) phenomenon in dual frequency is proposed, which originates from the EP‐based effect. EP generation is observed in the loss‐assisted system by optimizing structure parameters. At EPs, when the incident light is x‐ or y‐polarized, ideal backward or forward reflectionlessness is spotted at 8.86 and 14.97 GHz, respectively. In contrast, the polarization state of the incident light has great influence on the UR phenomenon and controllably switches the reflected directions and frequencies. Furthermore, when the polarization angle of the incident light is 50°, bilateral unidirectional reflectionlessness can be observed at two characteristic frequencies. The study on the non‐Hermitian metasurface provides experimental solutions toward EP‐based effects, which are greatly beneficial to the development of unidirectional devices.

Extremely asymmetric absorption and reflection near the exceptional point for three-dimensional metamaterial

“…However, in practical applications, it can be cumbersome to introduce and manipulate gain factors in metamaterial platforms and to balance them with loss factors [33,34]. Recent research shows that all-passive systems without optical gain can be engineered to demonstrate EP-related phenomena [10,[35][36][37][38][39][40]. In [12], Li et al demonstrated a passive asymmetric acoustic absorber at an EP with a compact configuration and deepsubwavelength thickness which achieves EP-induced tunable asymmetric absorption.…”