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

Abstract

Based on the non‐Hermitian theory, a unidirectional reflectionless (UR) effect with polarization dependence is realized in a metasurface. The frequency and direction of the nonreciprocal effect can be switched by changing the polarization state of the incident light, and a bilateral UR phenomenon is observed at a certain polarization angle, which enables the development of nonreciprocal devices. 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.