▎ 摘　　要

In this paper, the sensitivities of graphene based surface plasmon resonance (SPR) biosensors with gold (Au), silver (Ag) and copper (Cu) layers are numerically analyzed and compared in the visible region. As the wavelength of the incident light increases, the sensitivity of a monolayer graphene based SPR biosensor with a specific metal (Au, Ag or Cu) layer firstly increases to a maximum value (called peak sensitivity), and then decreases. It is found that the peak sensitivity of a monolayer graphene based SPR biosensor with Ag layer (300.26 degrees/RIU) is 119% or 200% higher than the one of SPR biosensor with Au (137.02 degrees/RIU) or Cu (136.24 degrees/RIU) layer. In addition, with the increase of number of graphene layers, the peak sensitivity of the proposed SPR sensor with different metal layer decreases, but the resonance wavelength increases. Moreover, the origin of sensitivity enhancement is also investigated by analyzing the electric field intensity inside the proposed SPR biosensors. It is believed that a sensitivity comparison of graphene based SPR biosensors with Au, Ag and Cu layer is important and can be helpful for highly sensitive biosensors development.