基于超表面的超宽带线极化转换特性研究

Research on Ultra-wideband Linear Polarization Conversion Characteristics Based on Metasurfaces

极化转换在太赫兹调制领域具有重要的研究意义和应用价值。传统的极化转换器件存在尺寸大、集成度低、损耗高、带宽窄等诸多不足。该文提出一种对称“山”型超表面共振单元结构,可用于实现反射、透射极化转换器件的设计。其中反射型器件实现了极高极化转换率的宽带线极化转换,透射型器件实现了相对带宽达135.5%的超宽带线极化转换。采用各向异性理论分析了反射型器件产生极化转换的机制,并基于多重干涉理论对共振结构阵列与金属背板构成的类F-P腔进行了计算,计算结果与仿真吻合较好。进一步使用正交线栅类F-P腔与共振结构阵列,构成透射型器件,并深入分析了共振单元结构不同部分对宽带极化转换的贡献,讨论了不同结构形成的极化转换频段间的耦合方式。研究结果为基于固定相位差的超宽带偏振极化转换器件的实现以及超表面类F-P腔应用提供了新的思路。

Polarization conversion has important research significance and application value in the field of terahertz modulation.Traditional polarization conversion devices have many shortcomings,such as large size,low integration,high loss and narrow bandwidth.In this paper,a symmetrical"mountain"structure of resonator is proposed,which can be used to realize the design of reflection and transmission polarization conversion devices.The reflective device realizes the linear polarization conversion with the properties of broadband and extremely high polarization conversion rate.The transmissive device realizes 135.5%ultrabroadband linear polarization conversion.The anisotropy theory is used to analyze the mechanism of polarization conversion in reflective devices,and the Fabry-Pérot-like cavity formed by the resonant structure array and the metallized ground plane is calculated based on the multiple interference theory.The calculated results are in good agreement with the simulations.Furthermore,the Fabry-Pérot-like cavity composed of orthogonal grating and the resonator are used to form a transmissive device.The contributions of different parts of the resonator to the broadband polarization conversion are analyzed.Contribution of different structures validates results for broadband polarization conversion.The research results provide a new idea for the realization of ultra-wideband polarization conversion devices based on fixed phase difference and the application of Fabry-Pérot-like cavities in metasurfaces.