Half-side gold-coated hetero-core fiber for highly sensitive measurement of a vector magnetic field

A highly sensitive surface plasmon resonance fiber sensor for a vector magnetic field is proposed. The sensor is composed of a half-side gold-coated multimode-single-mode-multimode hetero-core fiber structure encapsulated with ferrofluids. The half-side gold film on the fiber not only produces the surface plasmon resonance, but also breaks the centrosymmetry of the light field in the fiber. Moreover, the magnetic-field-dependent anisotropy of the surrounding ferrofluids makes the sensor sensitive to both the intensity and direction of the magnetic field. Owing to the unique half-side coating configuration and the resulting enhancement of the evanescent field, the sensor can achieve a sensitivity as high as 1008 pm/Oe to the magnetic field intensity. The proposed sensor, possessing advantages such as high sensitivity, ease of fabrication, and low cost, has potential in the detection of a weak vector magnetic field. (C) 2020 Optical Society of America