A plasmon-induced transparency (PIT) effect based on an asymmetric graphene loop structure has been proposed and investigated in this paper. The microstructure consists of a pair of graphene square loops and a dielectric substrate. The calculated results show that the transparency peak can be produced at 5.68 THz by the frequency detuning between two different graphene square loops. The geometric parameters of microstructure, such as the coincidence degree between two square loops, the length and the width of two square loops, will affect the position of PIT-window. Moreover, by adjusting the Fermi level of graphene through external gate voltage, the PIT-window can be dynamically tuned. Importantly, the PIT-window in graphene metamaterials can also serve as the amplitude modulator at the fixed frequency and the refractive index sensor. In addition, an improved microstructure is proposed for realizing the multi-PIT-window. The amplitude modulation of multi-PIT-window can be adjusted up to 53% by controlling the coupling distance, which has certain application prospects in the fields of double-channel filters, optical switches, and modulators.

本文提出并研究了基于不对称石墨烯环结构的等离子体诱导透明 (PIT) 效应。微结构由一对石墨烯方形环和一个介电基板组成。计算结果表明，通过两个不同石墨烯方形环之间的频率失谐，可以在 5.68 THz 处产生透明度峰值。微结构的几何参数，如两个方环的重合度、两个方环的长度和宽度，都会影响 PIT 窗口的位置。此外，通过外部栅极电压调整石墨烯的费米能级，可以动态调整 PIT 窗口。重要的是，石墨烯超材料中的 PIT 窗口还可以作为固定频率的调幅器和折射率传感器。此外，提出了一种改进的微结构来实现多 PIT 窗口。通过控制耦合距离，多PIT窗口的调幅可达53%，在双通道滤波器、光开关、调制器等领域具有一定的应用前景。