Refractive index sensing characteristics of PCF-SPR based on dual-plasmon materials

Abstract In this paper, a photonic crystal fiber (PCF) refractive index sensor based on surface plasmon resonance with dual plasmonic materials (indium tin oxide and gold) is proposed. We innovatively designed a dual-core PCF structure and pore arrangement effectively enhancing the coupling effect. Using two different plasma materials, phase matching is achieved at two different wavelengths for the evanescent and surface plasmon waves, resulting in dual resonance peaks. The refractive index sensing is accomplished by measuring the dual-peak resonance shift, which expands the detection wavelength and RI detection ranges. The sensor can detect analytes with refractive indices ranging from 1.32 to 1.43 at wavelengths between 0.4 µ m and 1.4 µ m. We optimized the PCF structure and studied the sensing performance of the sensor, improving its sensitivity. Simulation results indicate that the designed PCF sensor exhibits outstanding maximum dual-peak shift sensitivity, reaching up to 28 000 RIU −1 , along with maximum amplitude sensitivity and wavelength sensitivity of 18 500 RIU −1 and 34 500 RIU −1 , respectively, in the direction of y -polarization. Furthermore, the sensor achieves high resolution, and the figure of merit (FOM) values can reach up to 5.134 × 10 −7 and 2758. Consequently, the proposed sensor can provide high-precision and extensive-range measurements of solution refractive indices within the visible and infrared light spectrum, and it holds potential application prospects in numerous fields, such as food safety testing and chemical substance detection.