A High Sensitivity and Wide RI Range PCF-SPR Sensor and the Effect of Specific Pores on Sensing Performance

A PCF-SPR sensor was theoretically proposed with high sensitivity and a wide RI range. The sensor design employs a photonic bandgap structure with a hexagonal pore distribution. The PCF sensor demonstrated high sensitivity for both x-polarized and y-polarized light, achieving maximum sensitivities of 14,250 nm/RIU and 14,000 nm/RIU, respectively. Furthermore, the sensor is capable of detecting RI variations within the range of 1.19–1.53. Specific pore configurations were studied for their effects on sensing performance, revealing that both RI detection region and maximum wavelength sensitivity (WS) decrease as the pores between the gold and analyte move outward. As the core analyte diameter increases, the RI detection range of the PCF sensor decreases. However, the maximum WS increases with an increase in the core diameter. Increasing the pitch causes an increase in RI, while the maximum WS increases and then decreases. The study also shows that a regular hexagonal air hole distribution will only result in quadrupole resonance, whereas a quasi-regular hexagonal air hole distribution will show dipolar resonance. Dipolar resonance can extend the working wavelength to the mid-infrared range and improve both the RI range and sensitivity. The influence of air holes on the RI detection range can be explained by the equivalent medium method, and the influence on the sensitivity can be explained by the optical transmission theory.