High-Speed Traveling-Wave Modulator Based on Graphene and Microfiber

The two-dimensional graphene has an extremely high carrier mobility that can potentially offer an electrical bandwidth of over 500 GHz. However, the bandwidth of the reported graphene-based modulators is only a few tens of gigahertz due to the limitation of the RC constant rather than the carrier transit time. In this paper, a high-speed traveling-wave electro-optic modulator based on a graphene/microfiber structure is proposed and investigated for the first time to the best of our knowledge. The all-in-fiber electro-optic modulation in the graphene/microfiber-modulator is achieved by changing the Fermi level of graphene during its interaction with the evanescent wave of the microfiber. The active length of the modulator is 1.372 mm with a V_π of 4.9 V. The coplanar strip electrodes have a characteristic impedance of 54 ω and a microwave attenuation of 0.967 dB/mm. The mismatch between the microwave and the optical group velocity is 7.38%. A very high speed of 82 GHz 3-dB bandwidth is achieved.