Surface Plasmon Resonance Sensor Based on a Novel D-Shaped Photonic Crystal Fiber for Low Refractive Index Detection

A novel D-shaped photonic crystal fiber refractive index sensor based on surface plasmon resonance (SPR) is proposed and numerically studied. Different from the normal D-shaped structures, we here used an open-ring channel coated with gold film to excite the plamonic modes. The coupling properties and sensing performance of this structure are analyzed using finite element method. Simulation results indicate that the sensor has a sensing range from 1.20 to 1.29. When the analyte refractive index (RI) is above 1.25, the anti-crossing effect starts to appear, and the peak loss of the loss spectra remains nearly constant with increasing RI. The maximum spectral sensitivity of 11055 nm/RIU and high resolution of $9.05\times 10^{-6}$ RIU can be obtained at 1.29. For the purpose of optimizing sensing performance, the effects of the structure parameters on the resonant spectra are also studied. The excellent sensing performance makes the proposed SPR sensor a competitive candidate in low refractive index detection applications.