Magnetic Field Sensor Based on a Fiber Taper Integrated in a Magnetic Polymer Micro-Ellipsoid

In this article, a highly sensitive magnetic field sensor based on a fiber taper integrated in a magnetic polymer micro-ellipsoid was proposed. The magnetic polymer micro-ellipsoid was formed by coating and curing the magnetic polymer material on the fiber taper. The length of the fiber taper is 600 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>. The lengths of the magnetic polymer micro-ellipsoid along short- and long-axis directions are 830 and 1250 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>, respectively. The incident light was divided into two beams at the fiber taper. The two beams transmitting along the fiber taper and magnetic polymer micro-ellipsoid separately form the Mach–Zehnder (M-Z) interference. The refractive index and the interference length change along with the magnetic field variation, which results in the interference spectrum shift. The magnetic field sensitivity is up to −61.8 pm/mT. The sensor will have important applications in medical care, aerospace, and other fields due to its high sensitivity, simple preparation, and low cost.