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

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 similar to 7.5 dB (similar to 2.5 dB) and a modulation efficiency of similar to 0.2 dB mW(-1) (similar to 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.