All-solid-state Energy Storage Materials and Devices Key Laboratory of Hunan Province, College of Information and Electronic Engineering, Hunan City University, Yiyang 413000, China.
Phys Chem Chem Phys. 2023 Jun 28;25(25):17034-17042. doi: 10.1039/d3cp01370g.
A fully continuous geometric center symmetric cross-shaped graphene structure is proposed. Each cross-shaped graphene unit cell is composed of a central graphene region and four completely symmetric graphene chips, where each graphene chip acts as both bright and dark modes simultaneously, while the central graphene region always acts as the bright mode. Through destructive interference, the structure can realize the single plasmon-induced transparency (PIT) phenomenon, where the optical responses are independent of the polarization direction of the linearly polarized light due to the symmetry of the structure. Combining numerical simulations with coupled mode theory (CMT) calculations, the modulation of the Fermi energy of graphene to the optical spectra is investigated. The results show that the spectra are blue shifted as the Fermi energy increases, and the absorption of the two absorption peaks is basically equal (48.7%) when the Fermi energy increases to 0.667 eV. Theoretical calculations show that the slow light performance of the designed structure enhances with the increase of Fermi energy, where the maximum group index is high up to 424.73. Furthermore, it is worth noting that the electrode can be made very small due to its fully continuous structure. This work provides guidance in terms of terahertz modulators, tunable absorbers, and slow light devices.
提出了一种完全连续的几何中心对称十字型石墨烯结构。每个十字型石墨烯单元由一个中心石墨烯区域和四个完全对称的石墨烯芯片组成，其中每个石墨烯芯片同时充当亮模和暗模，而中心石墨烯区域始终充当亮模。通过相消干涉，该结构可以实现单等离子体诱导透明（PIT）现象，由于结构的对称性，光学响应与线偏振光的偏振方向无关。通过数值模拟与耦合模理论（CMT）计算相结合，研究了石墨烯费米能级对光学谱的调制。结果表明，随着费米能级的增加，光谱发生蓝移，当费米能级增加到 0.667eV 时，两个吸收峰的吸收基本相等（48.7%）。理论计算表明，设计结构的慢光性能随着费米能级的增加而增强，其中最大群折射率高达 424.73。此外，值得注意的是，由于其完全连续的结构，电极可以做得非常小。这项工作为太赫兹调制器、可调谐吸收器和慢光器件提供了指导。
