Li Liangwei, Pan Weikang, Wang Yingying, Jin Xiangyu, Chen Yizhen, Zhu Zhiyan, Liu Muhan, Li Jianru, Shi Yang, Li Haodong, Ma Shaojie, He Qiong, Zhou Lei, Sun Shulin
Shanghai Engineering Research Centre of Ultra Precision Optical Manufacturing, Department of Optical Science and Engineering, School of Information Science and Technology, Fudan University, Shanghai 200433, China.
Yiwu Research Institute, Fudan University, Chengbei Road, Yiwu 322000, China.
Nanomaterials (Basel). 2024 Sep 3;14(17):1438. doi: 10.3390/nano14171438.
Delaying an electromagnetic (EM) wave pulse on a thin screen for a significant time before releasing it is highly desired in many applications, such as optical camouflage, information storage, and wave-matter interaction boosting. However, available approaches to achieve this goal either require thick and complex systems or suffer from low efficiencies and a short delay time. This paper proposes an ultra-thin meta-platform that can significantly delay an EM-wave pulse after reflection. Specifically, our meta-platform consists of three meta-surfaces integrated together, of which two are responsible for efficiently coupling incident EM-wave pulse into surface waves (SWs) and vice versa, and the third one supports SWs exhibiting significantly reduced group velocity. We employ theoretical model analyses, full-wave simulations, and microwave experiments to validate the proposed concept. Our experiments demonstrate a 13 ns delay of an EM pulse centered at 12.975 GHz, enabled by a λ/8-thick and 38-λ-long meta-device with an efficiency of 32% (or 70%) with (or without) material loss taken into account. A larger delay time can be enabled by devices with larger sizes considering that the SWs group velocity of our device can be further reduced via dispersion engineering. These findings establish a new road for delaying an EM-wave pulse with ultra-thin screens, which may lead to many promising applications in integration optics.
在许多应用中，如光学伪装、信息存储和波-物质相互作用增强，非常希望在薄屏幕上延迟电磁（EM）波脉冲很长时间后再释放它。然而，现有的实现这一目标的方法要么需要厚且复杂的系统，要么效率低且延迟时间短。本文提出了一种超薄超材料平台，它可以在反射后显著延迟EM波脉冲。具体而言，我们的超材料平台由三个集成在一起的超表面组成，其中两个负责将入射的EM波脉冲有效地耦合到表面波（SWs）中，反之亦然，第三个支持群速度显著降低的表面波。我们采用理论模型分析、全波模拟和微波实验来验证所提出的概念。我们的实验表明，一个中心频率为12.975 GHz的EM脉冲延迟了13 ns，这是由一个厚度为λ/8、长度为38λ的超材料器件实现的，考虑（或不考虑）材料损耗时效率为32%（或70%）。考虑到我们器件的表面波群速度可以通过色散工程进一步降低，尺寸更大的器件可以实现更大的延迟时间。这些发现为用超薄屏幕延迟EM波脉冲开辟了一条新途径，这可能会在集成光学中带来许多有前景的应用。
