Design and analysis of graphene slot waveguide micro-ring modulator with high extinction ratio and bandwidth

A high-performance graphene electro-refractive and electro-absorption optical micro-ring modulator is investigated. Various graphene strip and slot waveguides are studied for their potential to enhance modulation efficiency due to the unique properties of graphene, such as its exceptional optical and electrical characteristics. The bandwidth (BW) of the presented ring modulator in critical coupling conditions is enhanced by optimizing active region length and oxide thickness. According to the simulation results, a double layer graphene ring modulator (DLG-RM) based on a slot waveguide exhibits superior modulation efficiency, with an extinction ratio (ER) of more than 60 dB, an electro-optic bandwidth of more than 40 GHz, and power consumption of less than 40 fJ/bit for phase as well as amplitude modulation at around 1550 nm. For efficient coupling between the strip and the slot waveguide, an optimized symmetric multi-mode interferometer (MMI) is implied. By proper design of DLGRM, the vital tradeoff between ER and BW is enhanced, and a device with a small footprint and CMOS compatibility is proposed for optical interconnects.