No-Core Hollow Fiber-Based SPR Sensor for Ultra-Wide Range of Refractive Index Detection

A no-core hollow fiber-based surface plasmon resonance (SPR) sensor is proposed to detect an ultra-wide range of refractive index (RI) in this letter. The no-core fiber takes the central air hole coated with a gold layer as an analyte channel, and the external environment as a cladding, which ensures that the incident light can propagate in the fiber at an ultra-wide RI range, and thus implementing the detection. We theoretically investigate the sensing performance of the sensor at an ultra-wide range of RI, and also the impact of the size of the central hole. The results indicate that the sensor can effectively work at the RI covering, but not limited to the range from 1.28 to 1.7. The higher sensitivities appear when the RI of the analyte is close to that of the fiber material, and the maximum sensitivity is 4981 nm/RIU at 1.5 of the analyte RI. In contrast with the majority of the previous SPR sensors for detection of wide RI, the proposed sensor has the advantages of simple structure, easy operation and ultra-wide range, and would be more competitive in the SPR sensing fields.