Broadband, High-Efficiency and Wide-Incident-Angle Anomalous Reflection in Groove Metagratings,Annalen Der Physik

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Broadband, High-Efficiency and Wide-Incident-Angle Anomalous Reflection in Groove Metagratings
Annalen Der Physik ( IF 2.2 ) Pub Date : 2021-06-28 , DOI: 10.1002/andp.202100149
Chuanbao Liu _{1,

2} , Jingjin He ₃ , Ji Zhou ₁ , Jianchun Xu ₄ , Ke Bi ₄ , Junhong Chen ₂ , Lijie Qiao ₃ , Yang Bai ₃

Affiliation

In this paper, some nonplanar metagratings with multilevel asymmetric grooves are demonstrated to produce broadband and high-efficiency anomalous reflection in wide-incident-angle range. First, bipartite metagrating with two asymmetric grooves per unit cell is proposed and optimized by machine learning. It can not only realize a high efficiency (≈88.8%) and large-angle (≈70°) anomalous reflection under normal incidence, but also preserve the high performance over broad bandwidth (12.0–20.0 GHz) and wide-incident-angle range. Furthermore, to improve the large-angle anomalous reflection at low frequencies, a tripartite metagrating is designed. The participation of more cavity modes makes the metagrating achieve the anomalous reflection with an efficiency greater than 90% over a broader bandwidth from ±1st Rayleigh anomalies to 20.0 GHz (even higher) and a wide range of incident angles from −70° to 70°, which is verified by the experimental measurement. Especially at an incident angle of 20°, the high-efficiency anomalous reflection is sustained over an ultrabroad frequency range from 9.7 to 21.2 GHz, i.e., a fractional bandwidth of 74.4%. The excellent performance of anomalous reflection and relatively simple structures endow the asymmetric groove metagratings with abundant functions, such as ideal three-channel retroreflector and abnormal reflector, and make them attractive in highly efficient and extreme wave manipulation.

中文翻译：

宽带、高效率和宽入射角的槽重反射异常反射

在本文中，一些具有多级非对称凹槽的非平面超光栅被证明可以在宽入射角范围内产生宽带和高效的异常反射。首先，提出并通过机器学习优化了每个晶胞具有两个不对称凹槽的二分元光栅。它不仅可以在法向入射下实现高效率（≈88.8%）和大角度（≈70°）异常反射，还可以在宽带宽（12.0-20.0 GHz）和宽入射角范围内保持高性能. 此外，为了改善低频下的大角度异常反射，设计了三方偏光栅。更多腔模的参与使得元光栅在从±1st Rayleigh异常到20的更宽带宽内以大于90%的效率实现异常反射。0 GHz（甚至更高）和从 -70° 到 70° 的大范围入射角，这已通过实验测量得到验证。特别是在入射角为 20° 时，高效异常反射在 9.7 至 21.2 GHz 的超宽频率范围内持续，即分数带宽为 74.4%。反常反射的优异性能和相对简单的结构赋予了非对称凹槽变光栅丰富的功能，如理想的三通道后向反射器和异常反射器，使其在高效和极端的波浪操纵中具有吸引力。2 GHz，即 74.4% 的部分带宽。反常反射的优异性能和相对简单的结构赋予了非对称凹槽变光栅丰富的功能，如理想的三通道后向反射器和异常反射器，使其在高效和极端的波浪操纵中具有吸引力。2 GHz，即 74.4% 的部分带宽。反常反射的优异性能和相对简单的结构赋予了非对称凹槽变光栅丰富的功能，如理想的三通道后向反射器和异常反射器，使其在高效和极端的波浪操纵中具有吸引力。

更新日期：2021-06-28

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