High-speed waveguide-coupled graphene-on-graphene optical modulators

An electro-absorption optical modulator concept based upon a dual-graphene layer is presented. The device consists of a silicon-on-insulator waveguide upon which two graphene layers reside, separated by a thin insulating region. The lower graphene acts as a tunable absorber, while the upper layer functions as a transparent gate electrode. Calculations based upon realistic graphene material properties show that 3-dB bandwidths over 120 GHz (30 GHz) are achievable at near- (lambda = 1.55 mu m) and mid- (lambda = 3.5 mu m) infrared bands. The effect of background doping and potential fluctuations on the bandwidth, modulation depth, and insertion loss are also quantified. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704663]