Numerical investigation of a gold-nanowire-assisted PCF-SPR biosensor for refractive index sensing of blood constituents

A photonic crystal fibre surface plasmon resonance (PCF-SPR) biosensor based on two symmetrically arranged gold nanowires is proposed for refractive-index (RI) sensing of blood constituents. One gold nanowire is placed on each of the upper and lower silica-analyte interfaces to enhance coupling between the core-guided and surface plasmon polariton (SPP) mode. Key structural parameters of the proposed sensor, including the air-hole diameters, pitch, and gold nanowire diameter, were numerically investigated using the finite element method (FEM). The optimized sensor exhibits a pronounced redshift of the resonance wavelength as the analyte RI increases, and distinct resonance peaks are obtained for the RI values assigned to representative blood constituents. Within the investigated RI range, the sensor achieves a maximum wavelength sensitivity (WS) of 16200 nm/RIU, maximum figure of merit (FOM) of 276 RIU−1. These results indicate the design’s potential for label-free RI sensing; biochemical specificity and an experimental detection limit require further validation..