Tang Linlong, Wei Wei, Wei Xingzhan, Nong Jinpeng, Du Chunlei, Shi Haofei
Opt Express. 2018 Feb 5;26(3):3709-3722. doi: 10.1364/OE.26.003709.
The mechanism of propagating graphene plasmons excitation using a nano-grating and a Fabry-Pérot cavity as the optical coupling components is studied. It is demonstrated that the system could be well described within the temporal coupled mode theory using two phenomenological parameters, namely, the intrinsic loss rate and the coupling rate of a graphene plasmonic mode, and their analytical expressions are derived. It is found that the intrinsic loss rate is solely determined by the electron relaxation time of graphene, while independent of the field distributions of the modes. Such result originates from the negligible magnetic field energy of the graphene plasmonic mode. The coupling rate is governed by the optical coupling components parameters, and varies periodically with the Fabry-Pérot cavity length. By modulating the two rates, quality factors and absorption rates can be adjusted. Furthermore, it is revealed that low refractive index of the Fabry-Pérot cavity material is vital to the enlargement of tunable band, and the underlying physics is discussed. Such plasmon excitation configuration is insensitive to light incident angle and could serve as a platform for many tunable infrared photonic device, such as surface-enhanced infrared absorption spectroscopies, infrared detectors and modulators.
研究了使用纳米光栅和法布里-珀罗腔作为光耦合组件来激发石墨烯表面等离激元的传播机制。结果表明，利用两个唯象参数，即石墨烯表面等离激元模式的本征损耗率和耦合率，该系统可以在时域耦合模理论中得到很好的描述，并推导了它们的解析表达式。研究发现，本征损耗率仅由石墨烯的电子弛豫时间决定，而与模式的场分布无关。这一结果源于石墨烯表面等离激元模式可忽略不计的磁场能量。耦合率由光耦合组件参数决定，并随法布里-珀罗腔长度呈周期性变化。通过调制这两个速率，可以调整品质因数和吸收率。此外，研究表明，法布里-珀罗腔材料的低折射率对于扩大可调谐波段至关重要，并讨论了其潜在的物理原理。这种表面等离激元激发结构对光入射角不敏感，可作为许多可调谐红外光子器件的平台，如表面增强红外吸收光谱、红外探测器和调制器。
