Graphene electro-optic modulator with 30 GHz bandwidth

Graphene has generated exceptional interest as an optoelectronic material(1,2) because its high carrier mobility(3,4) and broadband absorption(5) promise to make extremely fast and broadband electro-optic devices possible(6-9). Electro-optic graphene modulators previously reported, however, have been limited in bandwidth to a few gigahertz(10-15) because of the large capacitance required to achieve reasonable voltage swings. Here, we demonstrate a graphene electro-optic modulator based on resonator loss modulation at critical coupling(16) that shows drastically increased speed and efficiency. Our device operates with a 30 GHz bandwidth and with a state-of-the-art modulation efficiency of 15 dB per 10 V. We also show the first high-speed large-signal operation in a graphene modulator, paving the way for fast digital communications using this platform. The modulator uniquely uses silicon nitride waveguides, an otherwise completely passive material platform, with promising applications for ultra-low-loss broadband structures and nonlinear optics.