Surface plasmon resonance refractive index sensor based on D-type ZBLAN photonic crystal fiber

Abstract This study presents a ZBLAN-based D-type photonic crystal fiber (PCF) surface plasmon resonance (SPR) refractive index (RI) sensor. Traditional silica substrate face challenges in detecting high-RI liquids and have limited RI detection ranges. To address this, we utilize high-RI ZBLAN glass as the substrate material and design a cladding with an outer three-layer ortho-octagonal and inner ortho-hexagonal air-hole structure, polished and coated with a gold film to excite SPR. The loss spectrum divides into two resonance channels for RI sensing within 1.420–1.466 and 1.467–1.475. Finite element method analysis evaluates the sensor’s performance, including the impact of air-hole diameter, gold film thickness, air-hole spacing, and polishing depth on the full width at half maximum (FWHM) of the loss spectrum and sensitivity. Results indicate that structural parameter changes primarily affect FWHM, with minimal influence on sensitivity. The two resonance channels achieve maximum sensitivities of 9000 nm RIU −1 and 13000 nm RIU −1 , highest resolutions of 1.11 × 10 −5 RIU and 7.69 × 10 −6 RIU, maximum amplitude sensitivities of 102.11 RIU −1 and 102.51 RIU −1 , and Q values of 46.27 and 31.52. This approach offers a promising method for developing high-sensitivity, wide-range RI PCF-SPR sensors, demonstrating strong potential in RI measurement applications.