Refractive index sensor based on a D-shaped Photonic Crystal Fiber with a gold layer coated by a graphene sheet

The investigation of a graphene-based D-shaped photonic crystal fiber sensor for operation at the visible and infrared spectra is presented. The cross section of the proposed sensor is designed by polishing a PCF with hexagonal array of air holes. A gold layer covered by a thin graphene film is deposited on the flat surface of the fiber while the analyte to be sensed can be dropped on the top of this coating. The sensing properties arise from the surface plasmon resonances (SPR) at the interface between the fiber core and the conducting slab. The sensor can reach an average sensitivity of 2815 nm/RIU for the case without graphene and 4061.8 nm/RIU when the graphene film is deposited on the top of the gold layer, allowing a resolution of 2.46x10-5 RIU for an optical spectrum analyzer with resolution of 0.1 nm. Moreover, the sensitivity can reach 7900 nm/RIU for analytes with refractive index greater than 1.37.