The frequency mixing property of time-modulated metasurfaces, attributed to the well-known phenomenon of temporal photonic transition, has led to several exotic functionalities in the last lustrum. Based on this concept, we demonstrate the possibility of achieving nonreciprocal responses in the near-infrared regime via combining a time-modulated platform and a static high-Q metasurface. In particular, the temporal metasurface is designed to up-convert the incident tone to the first higher-order harmonic, while the static platform is implemented to establish a filtering behavior with respect to the incident frequency. It is shown that while the receiver port acquires the transmitted signal in the forward direction, the amount of received power becomes negligible under the time-reversal scenario, which indicates the presented configuration exhibits different optical responses from opposite directions. In addition, the role of operating wavelength and the modulation frequency on the power isolation level are investigated, and it is demonstrated that by appropriate selection, the isolation level can reach −30 dB. Since this is the first time a nonreciprocal response is obtained in the near-infrared regime via a pure temporal modulation, we believe the idea of this paper can be of utmost importance in various applications, such as tunable optical isolators.

中文翻译：

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通过透射时间调制超表面的光学非互易性

时间调制超表面的频率混合特性归因于众所周知的时间光子跃迁现象，导致了最后一个阶段的几个奇异功能。基于这个概念，我们展示了通过结合时间调制平台和静态高 Q 超表面在近红外区域实现单向响应的可能性。特别地，时间超表面设计用于将入射音调上转换为第一高次谐波，而静态平台用于建立关于入射频率的滤波行为。结果表明，当接收器端口在正向获取传输信号时，在时间反转情况下接收到的功率量变得可以忽略不计，这表明所呈现的配置表现出来自相反方向的不同光学响应。此外，研究了工作波长和调制频率对功率隔离水平的影响，证明通过适当的选择，隔离水平可以达到-30 dB。由于这是第一次通过纯时间调制在近红外区域获得非互易响应，我们相信本文的想法在各种应用中至关重要，例如可调谐光隔离器。