Highly Sensitive Surface Plasmon Resonance Sensor Based on Graphene-Coated U-shaped Fiber

A graphene-coated U-shaped fiber surface plasmon resonance sensor with high refractive index sensitivity is proposed. With the combination of graphene coating and U-shape design, the proposed sensor exhibits a significantly enhanced sensitivity as compared with the conventional Au-based straight fiber surface plasmon resonance sensor. The refractive index sensitivity of 15.52 μm/RIU (refractive index unit) is achieved by coating monolayer graphene on U-shaped fiber with a bent radius of 1.1 cm. A sensitivity enhancement factor of about 5-fold is obtained when compared with the conventional straight fiber surface plasmon resonance sensor with and without monolayer graphene coating. The effect of Au thickness, number of graphene layers, and the bent radius on the sensor performance was investigated. The high sensitivity of the proposed graphene-coated U-shaped fiber surface plasmon resonance sensor makes it a promising candidate for biosensing and chemical sensing.