Surface plasmon resonance refractive index sensor based on photonic crystal fiber covering nano-ring gold film

We propose a tunable wide-range surface plasmon induced refractive index optical sensor based on photonic crystal fiber (PCF) covered nano-ring gold film. The free electrons on the gold surface will resonate with photons to excite the attenuation and transmission of surface plasmon waves on the metal surface, when the vibrational frequencies of photons and electrons are the same. The refractive index analytes are very sensitive to SPR, which will be applied to PCF refractive index sensors. The finite element method (FEM) is used to analyze and simulate the sensing performance of the refractive index sensor. A kind of refractive index analyte is infiltrated into the outermost air holes of cladding. However, the resonance coupling between the fundamental mode and surface plasmon polariton (SPP) mode happens when the phase matching condition is matched. The resonance wavelength for 1st and 3rd peaks dependence on the refractive index analyte follows polynomial fitting law, and their fitness are 0.99605 and 0.99623, respectively. When the range of refractive index is from 1.33 to 1.39 and 1.40 to 1.43, the dependence of the resonant wavelength on the refractive index of the analyte follows a linear law and exhibits a relatively high sensitivity.