An all-optical modulator based on a stereo graphene–microfiber structure

Abstract

An in-line, all-optical fiber modulator based on a stereo graphene–microfiber structure (GMF) utilizing the lab-on-rod technique was demonstrated in this study. Owing to its unique spring-like geometry, an ultra-long GMF interaction can be achieved, and a modulation depth of ∼7.5 dB (∼2.5 dB) and a modulation efficiency of ∼0.2 dB mW−1 (∼0.07 dB mW−1) were demonstrated for two polarization states. The modulation depth and modulation efficiency are more than one order of magnitude larger than those of other graphene–microfiber hybrid all-optical modulators, although at the cost of a higher insertion loss. By further optimizing the transferring and cleaning process, the upper limit of the modulation depth is mainly determined by the loss from the intrinsic absorption, which depends on the light–graphene interaction. Then, the modulator can quickly switch between the on-state and the off-state with a theoretically maximized modulation depth of tens of decibels. This modulator is compatible with the current fiber-optic communication systems and may be applied in the near future to meet the impending need for ultrafast optical signal processing. A polarization-sensitive all-optical fiber modulator based on a graphene–microfiber structure has been demonstrated by researchers in China. All-optical modulators with high modulation speeds, sufficient modulation depth and wide optical bandwidth are needed to realize ultrafast optical signal processing. Now, Fei Xu and co-workers at Nanjing University have fabricated an all-optical fiber modulator whose modulation depth and efficiency are more than ten times greater than previous all-optical modulators based on graphene and microfibers. These properties originate from its very long interaction length resulting from its spring-like geometry. The researchers consider that even better performance can be achieved by using higher quality graphene and improving the transfer and wrapping of the graphene in the fabrication process. Since the modulator is compatible with existing fiber-optic communication systems, it may find rapid application for ultrafast optical signal processing.