Surface Plasmon Resonance Sensor Based on Microstructured Optical Fiber With Ring-Core Configuration

A novel surface plasmon resonance (SPR) sensor based on ring-core microstructured optical fiber with silver film is presented in this paper. Field leakage from the ring core to the central metal film excites plasmon polaritons. Through numerical simulation with the finite-element method, we found that fundamental modes and one of second-order modes have strong interaction with surface plasma modes. Analyzing coupling characteristics, results show that high sensitivity using linear fitting and narrow full-width at half-maximum (FWHM) can both be acquired in these two modes, which contributes to the highest value of figure of merit reaching 2203. The proposed model with two air-hole rings is easy to fabricate in the real operation. Finally, influences of different metal and geometrical parameters on sensing performance are also discussed for optimization further.