Switching freely between superluminal and subluminal light propagation in a monolayer MoS₂ nanoresonator

We theoretically propose a feasible scheme to advance or slow the propagation of light in a monolayer MoS₂ nanoresonator (NR). The scheme allows one to easily turn on or off the fast (superluminal) and slow (subluminal) light effects and switch freely between fast and slow light propagation by only adjusting the frequency or intensity of the pump field. As the exciton interacts strongly with the phonons in MoS₂, the slow light effect will appear along with a large dispersion with a very steep negative slope and a sharp absorption peak. Especially, the maximal group velocity index of the slow light in the monolayer MoS₂ NR can reach two orders of magnitude larger than that in a carbon nanotube resonator. These results provide a new way to measure the exciton-phonon coupling strength and may prove useful in device applications such as optical switching and optical signal processing.