Barati Sedeh Hooman, Mohammadi Dinani Hediyeh, Mosallaei Hossein
Metamaterials Lab, Electrical and Computer Engineering Department, Northeastern University, Boston, MA 02115, USA.
Nanophotonics. 2022 Jul 14;11(17):4135-4148. doi: 10.1515/nanoph-2022-0373. eCollection 2022 Sep.
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.
时间调制超表面的频率混合特性，归因于著名的时间光子跃迁现象，在过去五年中带来了几种奇异的功能。基于这一概念，我们展示了通过结合时间调制平台和静态高Q值超表面在近红外波段实现非互易响应的可能性。具体而言，时间超表面被设计用于将入射音调上转换为一阶高阶谐波，而静态平台则用于建立针对入射频率的滤波行为。结果表明，虽然接收端口在正向获取传输信号，但在时间反转情况下接收功率变得可以忽略不计，这表明所呈现的配置从相反方向表现出不同的光学响应。此外，研究了工作波长和调制频率对功率隔离水平的作用，并证明通过适当选择，隔离水平可以达到-30 dB。由于这是首次通过纯时间调制在近红外波段获得非互易响应，我们相信本文的想法在各种应用中，如可调谐光隔离器，可能至关重要。
