Ring-Core Photonic Crystal Fiber Sensor Based on SPR for Extra-Wide Refractive Index Detection

Spurred by the rapid development of fiber optic sensing technology, photonic crystal fiber (PCF) sensors based on surface plasmon resonance (SPR) have received widespread attention. However, they can only detect a narrow range, and the coating process is complex. Herein, a wide-range SPR sensor is designed. It consists of a ring-core PCF filled with plasmonic materials. Compared to the process of depositing a coating inside the air hole, the analyte and gold nanowires fill our PCF, thus simplifying the manufacturing complexity. The ring-core structure enhances the directional power transmission between the guided mode and the surface plasmon polariton (SPP) mode. The sensor is numerically analyzed using the finite element method (FEM). The results show that the PCF-SPR sensor has a wavelength sensitivity and amplitude sensitivity of 40,000 nm/RIU and 2141 RIU−1, and the resolution is 2.5 × 10−6 RIU−1 for the detection range of 1.13–1.45. The high-sensitivity sensor boasting a wide refractive index detection range performs better than conventional solid-core PCF-SPR sensors, boding well for biochemical sensing.