宽入射角高效宽带超表面太赫兹线极化转换器

Terahertz high-efficiency broadband metasurface polarization converter with wide incident angle

为解决当前太赫兹频段下的极化转换器件带宽窄和带内转换率低的问题,设计了一款基于超表面的高效率太赫兹线极化转换器。通过在两端增加一对谐振枝节的方法,将原本的单谐振频点变为2个,增加了极化转换器的工作带宽。另一方面,利用超表面在电磁谐振时的高阻抗表面特性,获得了极低的同极化反射系数,提高了带内的总体转换效率。仿真结果显示,该结构能够在0.401~0.555 THz的宽频带范围内实现高效率的线极化转换,相对带宽约为32.5%,带内转换率高于95%。在理论分析方面,通过对高转换率频率下的表面电流与相位的仿真,阐明了宽带高转换率的机理。研究了该结构对于太赫兹波入射角度的依赖性,结果表明,该结构在0°~40°的入射角范围内均可保持较好的极化转换性能。同时,这款极化转换器具有设计简单的优点,这些工作能够对宽带高效的超表面极化转换器件设计提供设计思路。

A high-efficiency broadband polarization converter based on metasurface is proposed in order to broaden the working bandwidth of the polarization converter in terahertz band as well as improving the polarization conversion ratio.By adding a couple of resonating branches,the original single resonating point is increased to two,dramatically increasing the working bandwidth of the polarization converter.The low co-polarized reflectance is acquired through the characteristic of high-resistance surface when the metasurface is under electro-magnetic resonance,which could enhance the overall polarization conversion rate.The simulation results illustrate that this structure is able to achieve high polarization conversion in 0.401-0.555 THz with conversion ratio above 95%.The mechanism for high-efficiency broadband polarization conversion is discussed through simulating the reflect phase and surface current distribution.The dependence of the structure on the incident angle of terahertz waves is studied.The results show that this structure is able to maintain high conversion ratio at incident angle within 0°-40°.In addition,this design has advantage of simple structure.These works can help in the design of broadband efficient metasurface polarization converter.