Sensitivity analysis of graphene multilayer based surface plasmon resonance biosensor in the ultraviolet, visible and infrared regions

The sensitivity of a gold–graphene-based surface plasmon resonance (SPR) biosensor with angle scanning was numerically analyzed in the ultraviolet, visible and infrared regions. By comparing the sensitivities of the proposed SPR biosensor for different wavelengths of incident light, we find that there is an optimal wavelength of incident light for the proposed SPR biosensor to achieve the highest sensitivity (called peak sensitivity) in the ultraviolet, visible and infrared regions. In addition, with the increases of the number of graphene layers, the optimal wavelength becomes larger (red shift), but the peak sensitivity increases first, and then decreases. When the number of graphene layers equals to 7, the maximum of peak sensitivity shows at 550 nm and reaches to 76.80°/RIU, which is 40% higher than the sensitivity at 630 nm (near a common-used wavelength 633 nm). Furthermore, the sensitivity decreases with the number of graphene layers increases at the wavelength less than 540 nm, while increases at the wavelength more than 570 nm. Moreover, the origin of sensitivity enhancement is also determined by analyzing the electric field intensity inside the proposed SPR biosensor.