设计了一种基于栅状结构石墨烯超材料的电控器件, 利用有限元分析方法研究了其太赫兹波偏振调制特性。结果表明：在0.1~2.0 THz的宽波段内, 平行于条带的偏振太赫兹波（TE）响应由石墨烯的Drude电导决定, 表现出强的均匀调制; 垂直于条带的偏振太赫兹波（TM）受石墨烯中等离子体效应的影响而基本透明。加栅压提高石墨烯的费米能级可以增强TE的衰减, 并使TM的等离子体峰蓝移; 石墨烯的面积占比越高, 器件的响应越强; 增大条带宽度会引起等离子体峰红移; 增加石墨烯层数可以使器件的偏振度进一步提高。以2 μm为周期, 条带宽为1.5 μm的6层石墨烯器件的可调偏振度在费米能级为0.8 eV时可以达到0.89。该工作为新型太赫兹偏振调制器件的设计提供了思路。

We design an electronic control device based on graphene metamaterial with grating structure and study its polarization modulation properties in the terahertz region by finite element analysis method. The results show that in a wide band range of 0.1-2.0 THz, a broadband modulation occurs in the transmission of polarized terahertz wave parallel to the band (TE). It can be attributed to the intraband determined Drude conductivity of graphene. However, because of the plasma effect of graphene metamaterial, the transmission of polarized terahertz wave perpendicular to the band (TM) is almost transparent in the same terahertz region. More calculations also prove that with the increase of Fermi level of graphene, the modulation of TE will be enhanced largely while the plasma peak of TM will be blue shift. Meanwhile, the modulation can be further enhanced by the increase of the area ratio of graphene and the number of graphene layers in the device. In addition, the increase of the band width can cause a red shift of the plasma peak. With 2 μm period and 1.5 μm band width, a tunable maximum polarization degree of 0.89 can be achieved with 6 layer graphene device at Fermi level of 0.8 eV. This work paves a way for new graphene based terahertz polarization modulator.