Low-threshold and high-extinction-ratio optical bistability within a graphene-silicon-based perfect absorber

Abstract

We propose and numerically simulate a kind of graphene-silicon-based perfect absorber which possesses high-quality optical bistability in the near-IR band. In the structure, monolayer graphene is sandwiched between two silicon layers and is coupled with a 1D dielectric grating. With the help of the absorption rate of the monolayer graphene and the leakage rate of the grating structure, the critical coupling condition is satisfied and the incident light can be almost completely absorbed by the graphene at the resonant wavelength, causing prominent enhancement of electric field and light-matter interaction. Considering the third-order susceptibility of silicon together with the electric field enhancement, the perfect absorber shows significant bistable characteristics with ultralow thresholds and ultrahigh extinction ratio.The demonstrated switching thresholds can be lower than 90 kW/cm 2 , which can be further cut down by changing the structural parameters. The extinction ratio of the bistable states reaches an ultrahigh level of over 30 dB, since the structure is critically coupled with no reflected light coming out at the off state. The proposed bistable structure with compact size, low thresholds and high extinction ratio can be of great applications in the optical communication field.