Field Enhancement Assisted Graphene-Based Microring Modulator for High Modulation Depth

This study aims at optimising the graphene coverage in a microresonator for the design of an efficient modulator by using a combination of graphene induced losses and phase shift. The graphene integration in the ring can provide tunability by means of altering the loss and coupling coefficient by changing the graphene coverage or its chemical potential. The fundamental parameters of graphene integrated all-pass ring resonator are extracted based on the transmission characteristics using finite-difference time-domain method. As compared to conventional graphene-oxide-semiconductor straight waveguide, graphene integrated on an all-pass ring resonator shows enhanced optical absorption and phase shift due to field enhancement factor. A modulator based on graphene tunable loss and phase shift is investigated taking into account the field enhancement factor. For 1.55 μm radiation and ring radius of 3.75 μm with 22% graphene coverage, a maximum modulation depth of 12.6 dB is demonstrated based on electrostatic control of graphene chemical potential. The proposed modulator can feature operational speed in the range of 10 GHz that is useful in a variety of electro-optic applications.