In this manuscript, we propose a tunable multifunctional reflection polarization converter based on a graphene sheet, which is decorated by a π-shaped carved-hollow array. Our design can achieve the linear-to-linear (LTL) polarization conversion with 3.58 THz bandwidth and two linear-to-circular (LTC) polarization conversion bands with opposite handedness, which originates from the excitation of the three graphene surface plasmons (GSPs) modes. The LTL polarization converter can be switched to the LTC polarization converter by only changing the medium height. The performances of this multifunctional reflection polarization converter under different geometric parameters, incident angles, and electron scattering time of graphene are investigated. Besides, it is found that the broadband of LTL and double bands of LTC have the blue shift with increasing the Fermi energy (E_f) of graphene. Especially, the conversion between line-to-left-circular and line-to-right-circular polarization converter can be achieved by changing E_f. All the simulation results are conducted by finite element method, and our design has potential applications in integrated terahertz systems.

中文翻译：

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基于具有π形空心阵列的石墨烯片的宽带线性到线性和双带线性到圆偏振转换器

在这份手稿中，我们提出了一种基于石墨烯片的可调多功能反射偏振转换器，其由 π 形雕刻空心阵列装饰。我们的设计可以实现线性到线性 (LTL) 偏振转换，具有 3.58 THz 带宽和两个具有相反旋向性的线性到圆形 (LTC) 偏振转换带，这源于三个石墨烯表面等离子体 (GSP) 的激发模式。LTL偏振转换器只需改变介质高度即可切换为LTC偏振转换器。研究了这种多功能反射偏振转换器在不同几何参数、入射角和石墨烯电子散射时间下的性能。除了，E _f ) 的石墨烯。特别是，可以通过改变E _f来实现线到左圆偏振转换器和线到右圆偏振转换器之间的转换。所有的模拟结果都是通过有限元方法进行的，我们的设计在集成太赫兹系统中具有潜在的应用。