High Figure of Merit Electro-Optic Modulator Based on Graphene on Silicon Dual-Slot Waveguide

Abstract

A novel electro-optic modulator based on graphene on silicon (GoS) dual-slot waveguide is proposed, utilizing the electro-absorption and electro-refraction effect of graphene. The optical mode in the waveguide can interact strongly with the upper graphene layer due to the enhancement of light intensity and poor mode confinement in the nanometer slot. The real part and imaginary part of effective modal index relate to the optical propagation phase and attenuation, respectively. Electro-absorption and electro-refraction modulators can be realized by reasonably tuning the chemical potential of graphene through an applied gate voltage. The geometric parameters of the GoS waveguide are well optimized. Simulation results show the phase shift can be linearly tuned from 0 to $\pi $ by changing the gate voltage from 1 to 5.4 V for a $70~\mu \text{m}$ -long GoS dual-slot waveguide. When this waveguide is used as electro-absorption modulator, the modulation depth and insertion loss are 25 and 0.09 dB, respectively. The 3-dB bandwidth is estimated to be 79.6 GHz. The power consumption is ~0.94 pJ/bit and ~1.42 pJ/bit for the electro-refraction and electro-absorption modulation, respectively. The FoM (modulation depth/insertion loss) is as high as 273. This GoS dual-slot waveguide modulator with merits of footprint-compact, energy-efficient, and CMOS compatible has potentials in on-chip optical interconnections.