The highly sensitive magnetic field sensor based on photonic crystal fiber filled with nano-magnetic fluid

A high-sensitivity magnetic field sensor based on dual-core photonic crystal fiber (PCF) is proposed and demonstrated. Two microholes are introduced into the two fiber cores which form two defect cores and the two microholes are assumed to be filled with nano-magnetic fluid. The transmission characteristics of the dual-core PCF are analyzed by finite element method (FEM). The transmission principle of light beam in the fiber cores is proposed and the feasibility of light beam transmission in the defect cores is demonstrated. We analyze the influences of the microhole diameter and magnetic field on the refractive index, effective mode area, birefringence and coupling length of the fiber modes. The influences of the structural parameters and fiber length on the sensitivity are also studied. The sensitivity increases firstly and then decreases with the increasing microhole diameter. And the sensitivity increases with the increasing fiber length. The resonance wavelength red shifts with the increasing magnetic field under the certain structural parameters and fiber length. The fringe spacing between adjacent magnetic fields becomes narrower as the magnetic field increases, in other words, the sensitivity decreases. The highest sensitivity is 948 pm/Oe at the magnetic field 50 Oe.