Refractive index and magnetic field sensing based on bent microfiber functionalized with graphene oxide

A bent tapered multimode fiber structure for refractive index (RI) and magnetic field sensing applications is proposed and investigated. The bent tapered region deposited with gold film to excite surface plasmon resonance (SPR) functions as the sensing area. Further surface functionalization with graphene oxide (GO) enhances the SPR effect. The high sensitivity of 5260.1 nm/RIU in the RI range of 1.33-1.37 is achieved. Magnetic fluid is used as the magneto-sensitive material, and the achieved magnetic field intensity and directional sensitivities are 7.08 nm/mT and 0.15 nm/°, respectively. The surface functionalization of GO extends the magnetic field sensor's detection range up to 30 mT. The proposed sensor features a simple structure, low cost, point-sensing capability, and excellent mechanical properties, making it highly suitable for various practical applications.