ABSTRACT We have numerically investigated the tunable surface plasmon in graphene square-nanoring structure. Due to an enhancement of the local field, graphene surface plasmons (GSPs) can be strongly confined in the graphene grating region. The expressions of the lifetime for resonant modes have been investigated with the the finite difference time domain (FDTD) simulations and the coupled mode theory (CMT). Altering the Fermi energy and varying the carrier mobility have an important influence in optimizing the light absorption and the lifetime of GSPs. The CMT theoretical results agree well with FDTD simulations. Besides, by utilizing the different inner length and the different refractive index of substrate material, we find that the absorption peak of the GSPs structure can be tuned in a wide wavelength range. Our proposed graphene gratings structure shows good prospects in the mid-infrared region, such as ultracompact tunable integrated modulators and absorbers.

中文翻译：

---

基于可调表面等离子体的石墨烯方形纳米光栅的寿命特性

摘要 我们已经对石墨烯方形纳米结构中的可调表面等离子体进行了数值研究。由于局部场的增强，石墨烯表面等离子体（GSP）可以被强烈地限制在石墨烯光栅区域中。已经使用有限差分时域 (FDTD) 模拟和耦合模式理论 (CMT) 研究了谐振模式的寿命表达式。改变费米能量和改变载流子迁移率对优化光吸收和 GSP 的寿命有重要影响。CMT 理论结果与 FDTD 模拟非常吻合。此外，通过利用衬底材料的不同内部长度和不同的折射率，我们发现 GSPs 结构的吸收峰可以在很宽的波长范围内进行调谐。