Slow light might find various potential applications, such as optical buffer, signal processing, and enhanced light-matter interactions. Due to the limitation of delay-bandwidth product, conventional slow-light systems can only operate within a narrow spectral band near the resonant frequencies. Slow light based on metallic nanometric optical structures has capability of overcoming the diffraction limit and enhancing localized optical field in nanometric domain, which can be further exploited in applications towards enhanced light-matter interactions, on-chip light spectrum, and light localization, etc.

Dr. Lin Chen and Prof. Guoping Wang from Wuhan University have previously proposed a kind of metallic grating structure for broadband plasmonic slow light in the visible and infrared domain. The relevant results have been published in Physical Review B (rapid communications) and Applied Physics Letters. Based on this research work, Dr. Lin Chen and his PhD student Tian Zhang from Wuhan National Lab for Optoelectronics (WNLO), cooperating with Prof. Xun Li from McMaster University, and Prof. Guoping Wang from Wuhan University, have recently proposed to realize broadband slow SPPs on a graphene monolayer on a silicon grating substrate. The group velocity of SPP mode can be reduced to be several hundred times smaller than that of light in the air. Meanwhile, we also predict the capability of dynamically tuning the chemical potential of graphene to release the slow SPP mode. This structure can be employed to enhance light-matter interactions, on-chip light localization, spectrum splitting, broadband light absorption. This work has been published in Optics Express (Vol. 21, pp. 28628-28637, 2013). Related research work was supported by the National Natural Science Foundation of China, and 973 Program.

Fig. 1 Schematics of a graphene monolayer on a silicon grating substrate

Fig. 2 Field intensity distributions on the graphene monolayer for different incident wavelengths.