Design and Performance Evaluation of an Ultra-Sensitive Plasmonic Sensor Using Photonic Crystal Fiber

This study proposes an ultra-sensitive Surface Plasmon Resonance (SPR) biosensor based on a gold-coated, circular-slotted Photonic Crystal Fiber (PCF) structure. The sensor operates via plasmonic interactions at the outer fiber surface, where the gold layer interfaces directly with the surrounding analyte. It exhibits consistent performance across a refractive index (RI) range of 1.32 to 1.40, with strong linearity and detection precision. At an RI of 1.39, the optimized design achieves maximum sensitivities of 1088.95 RIU<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> in amplitude and 6000 nm/RIU in wavelength. Finite element analysis confirms a pronounced linear response with optimal operation near a wavelength of 0.8 μm. The external sensing configuration enhances sensitivity while preserving fabrication feasibility. By combining structural simplicity with high performance, this design represents a significant advancement in PCF-based SPR biosensing for biological and chemical detection applications.