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Surface plasmon resonance biosensor based on graphene and grating excitation.

A surface plasmon resonance biosensor based on a graphene-decorated grating excitation structure is proposed in this paper. The biosensor consists of a three-layer structure, including a graphene layer, a grating layer, and a high refractive index layer. The material of the grating layer is silica. The graphene is physically deposited on the grating ridges. An incident light with transverse magnetic polarization is used to excite surface plasmons in the mid-infrared spectral region, which is highly localized at both ends of the graphene layer. The property of the sensor is improved by the high refractive index dielectric layer, which enhances the absorption of incident light and increases the depth of the spectra. The finite-difference time-domain method is used to simulate the property of the sensor. The structure of the sensor could be optimized by changing the structural parameters and comparing the simulation results. The effective refractive index (RI) on the surface and the wavelength of the reflective resonance absorption peak will be changed when the surface of graphene adsorbs the surrounding analyte. The results show that the relationship between the analyte RI and the resonance wavelength is linear. The measurement range of analyte RI is 1-1.8, and the sensitivity is 2780 nm/RIU.