Eccentric Core Photonic Crystal Fiber Magnetic Field Sensor Based on Surface Plasmon Resonance with Extremely High Linearity

A micro-polished eccentric core photonic crystal fiber magnetic field sensor based on surface plasmon resonance (PCF-SPR) with a ring-shaped opening is designed. In the sensor, metal nanowires are placed inside the ring-shaped opening to excite SPR to replace the traditional coating process and enhance the sensing stability. Aluminum and gold are assessed as the SPR materials. When Al is the plasmonic medium, the sensor has a wider detection range and higher figure of merit (FOM), but the linearity of the resonant wavelength (RW) is not satisfactory. On the other hand, when Au is the plasmonic medium, the sensor shows excellent magnetic field sensitivity and resolution, in addition to ultra-high linearity in the RW, making it more suitable for magnetic field detection. The structural parameters are optimized, and the effects of different metals and temperatures on the sensing properties are investigated numerically. The sensor with Al shows a detection range of 40–200 Oe, maximum magnetic field sensitivity of 3000 pm/mT, and R² of 0.99988, whereas the Au sensor exhibits a detection range of 40–150 Oe, maximum magnetic field sensitivity of 9000 pm/mT, and RW R² of 0.99995. The PCF-SPR magnetic field sensor boasts a simple structure, wide detection range, high sensitivity, and good linearity. It has broad application prospects in mineral resource exploration, seismic and tsunami monitoring, medical diagnostics, and other fields.