Broadband Graphene/TiO2 Optical Modulator Based on Hybrid Plasmonic Waveguide for Ultrafast Switching and Low-Voltage State

Abstract

This work presents a novel contribution to graphene/TiO2 electro-optical modulators based on silicon-on-silica waveguide with a hybrid plasmonic waveguide to achieve ultrafast switching and low-voltage states. Waveguide structure consists of a rectangular silicon core covered by a high relative permittivity TiO2 dielectric layer with two layers of graphene, air-clad, and silica lower cladding. Effective refractive indices can be tailored to support the propagation of the transverse magnetic mode with a suitable design related to an electro-absorption modulator for simulation results. Modulation depth and bandwidth were enhanced by the waveguide width and dielectric thickness, respectively. Maximum and minimum absorption depths at the driving voltage states can determine modulators. The simulation produced the highest efficient modulator with high speed at 3 dB bandwidth of 93.7 GHz using a low energy consumption of 210.6 fJ/bit, a small footprint (24 µm2), and a broad operating spectrum range from 1310 to 1550 nm. This is because the physical process acts according to the modulator at the Fermi energy of graphene and the structure of the waveguide. These modulators can have practical applications due to their distinctive advantages, including a small device footprint, low voltage operation, ultrafast modulation switching across a broad wavelength range, and low-energy operation.