High-sensitivity coreless fiber surface plasmon resonance refractive index sensor based on Au/TiO₂

Fiber-optic surface plasmon resonance (SPR) sensors play a critical role in applications requiring high sensitivity. This work proposes an SPR refractive index (RI) sensor based on a multimode-coreless-multimode fiber structure functionalized with Au/TiO₂nanofiber composites. Experimental results demonstrate that the TiO₂nanofiber/Au sensor achieves a sensitivity of 3687.65 nm RIU^-1and a figure of merit of 29.50 RIU^-1within the RI range of 1.333-1.380. These values represent a 2.05-fold enhancement over conventional Au-film sensors. The synergistic design optimizes multiple performance metrics, enabling broad applications in chemical detection, biosafety monitoring, micro-molecule analysis, biomedical sensing, and other high-sensitivity detection scenarios.