石墨烯作为一种单层碳原子厚度的二维材料,其在可见光和近红外波段的吸收率只有2.3%。这大大限制了其在太阳能电池、光电探测等领域的应用。本文提出一种金属介质组成的周期纳米结构,利用纳米结构中激发的磁激元共振(Magentic Polaritons,“MP”)效应,实现了石墨烯在近红外波段的吸收增强。利用有限元法的理论仿真,系统研究了纳米结构参数对石墨烯吸收特性的影响。结果表明,在特定结构参数下,能使石墨烯的吸收率增大16倍左右。利用Inductor-Capacitor(LC)电路模型成功解释了石墨烯的吸收增强的物理机制,预测了复合系统的磁激元共振峰波长,发现石墨烯的存在不影响磁激元共振峰的位置。文中提出的纳米结构在加工上易于实现,研究结果将在基于石墨烯的新型光电子器件的设计和实现方面有潜在应用价值。

Graphene,a two-dimensional monatomic layer of carbon material,shows its weak absorptance of only about 2.3% in the visible and near infrared region.This dramatically limits its application in graphene-based solar cells and photon detection.In this letter,we propose a metal-dielectric periodic nanostructure to enhance the absorptance of graphene based on the magnetic resonances.Using finite-element method,we numerically simulated the effect of the structural parameters of the nanostructure on the absorptance of graphene layer.Our calculations show that the absorptance of graphene can be enhanced by about 4 times with specific structural parameters.Inductor-capacitor (LC) circuit model is applied to reveal the mechanism behind the absorption enhancement of graphene.The LC model succeeds in predicting the magnetic resonances,which are independent of the presence of the graphene.Our proposed nanostructure,which is easy for practical fabrication,is expected to have potential applications in the design of novel graphene-based optical and optoelectronic devices.