本文基于新型材料狄拉克半金属(Dirac semimetals,DSs),设计了一款高纯度宽频带可调谐线偏振转换器,偏振转换率(PCR)超过99％的相对带宽为15.72％。在频段5.25～6.14 THz内,椭度角接近0°,偏振方位角约等于-90°。这种转换性能主要是源于顶层超表面的各向异性和局域的表面等离子体激元谐振(LSPRs)的激发。此外,通过改变费米能的大小可以使所设计的偏振转换器在不同的频带范围内实现宽频带偏振转换。最后,通过半解析的方法对偏振转换特性进行了理论分析。该设计在太赫兹通信、成像、无损检测等领域具有一定的应用价值,同时为宽频带可调谐太赫兹线偏振转换器的设计提供了新思路。

Based on the Dirac semimetals (DSs),which is a new type of material and also called as 3D graphene,a high purity broadband tunable linear polarization converter is designed,and of which the relative bandwidths with polarization conversion ratio (PCR) over 99％ can reach 15.72％.The ellipticity is close to 0° and the polarization azimuth angle is nearly equal to -90° within the frequency range of 5.25～6.14 THz.The good conversion performance originates mainly from the anisotropy of the top DSs metasurface and the excitation of local surface plasmon resonance (LSPRs) at the bottom layer.Furthermore,it is found that changing the Fermi energy can make the proposed polarization converter realize broadband and high efficiency polarization conversion in different frequency ranges.Finally,the polarization conversion characteristics are theoretically analyzed by a semi-analytical method.The design has potential applications in terahertz communication,imaging,nondestructive inspection,and other fields.Meanwhile it is an innovative idea for the design of broadband tunable terahertz linear polarization converter.