Evanescent Field-Modulated Magnetic Immune Sensor Based on Magnetic Fluid and Polymer Optical Fiber

A highly sensitive and simple design of intensity based magnetic field sensor is proposed and experimentally demonstrated with a safe data transformation by employing optical fiber as a magnetic resonance-compatible sensor. The middle section of polymer optical fiber (POF) with 1.5 cm length was tapered with different diameter and roughness. The as-prepared fibers were surrounded with various magnetic fluids (MF). In order to evaluate the MF influence on the sensing performance, experimental comparative behavior studies were performed with incorporating different as-synthesized MF at different volume concentrations of Fe
₃
O
₄
and various materials (Zn
_0.5
Mn
_0.5
Fe
₂
O
₄
and composite: Zn
_0.5
Mn
_0.5
Fe
₂
O
₄
-Fe
₃
O
₄
). The prepared nanoparticles were characterized by X-ray diffraction pattern, scanning electron microscopy, vibrating sample magnetometer, and atomic force microscopy. Characteristic results confirmed the formation of Fe
₃
O
₄
nanoparticles with height profile less than 10 nm and cubic spinel structure. The refractive index of the MF-coated fiber, acting as a fiber clad, is modulated corresponds to the applied magnetic field and thus, presents an attractive opportunity for magnetic sensing applications. The obtained results revealed that the proposed POF-based sensor with 0.5 mm diameter and average 12 nm surface roughness of POF coated with composite MF exhibited efficient response. The proposed device is capable of detecting magnetic field with linear response of over 99% in the wide range of 2.5-150 mT measurements.