LAUSR

Abstract This paper proposes a magnetic field sensor based on side-polished fiber and microspheres. We use side-polished fiber and SiO2 microspheres to form fiber microsphere cavity, and then package the fiber microspheres in a capillary filled with magnetic fluid form magnetic field sensor. By adding optical fiber microspheres, light propagates through the near-field coupling to the microspheres and directly arouse the whispering gallery modes. The WGM resonance formed in the microcavity will cause a resonance peak with an ultra-narrow spectral line-width in the transmission spectrum, which will improve the quality factor (Q) and figure of merit (FOM) of the sensor. The paper uses finite element analysis to simulation the mode transmission characteristics of side-polished fiber microspheres and the magnetic field sensing performance. The simulation results show that the magnetic field sensor has a strength sensitivity of up to 0.75 dB/Oe and the quality factor up to 2.5 × 10 4 , which has a refractive index sensitivity of 125 nm/RIU, and a maximum FOM of 2.5 × 103. The paper effectively improves the quality factor of the sensor, by adding a microsphere, which provides an alternative research platform for the development of new magnetic field sensors compatible with high-sensitivity sensing and high-precision detection.