High-Sensitivity Vector Magnetometer Based on Mach–Zehnder Interferometer Combined With Magnetostrictive Material

A highly sensitive vector magnetometer based on Mach-Zehnder interferometer (MZI) combined with Terfenol-D rod was proposed. Firstly, a single-mode fiber (SMF) without a coating layer is directly tapered to form an MZI, named MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub>. Due to the small cross-sectional area of MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub>, its strain sensitivity was experimentally obtained to be as high as -64.04 pm/le. Terfenol-D exhibits good stretchability under the influence of the magnetic field (MF), and the direction of stretchability is related to the direction of the MF. MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> is pasted on the Terfenol-D rod. MF causes expansion and contraction of Terfenol-D rod, which is equal to acting an axial strain on MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub>, indirectly achieving the MF measurement. The experimental outcomes indicate that the sensitivities of MF intensity and direction of MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> are -0.221 nm/mT and 0.0712 nm/°. To further enhance its sensitivity, we connect MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, which has a similar structure and free spectrum range to MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub>, in series with MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> to form a vernier effect (VE) sensor S<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> for MF vector measurement. The experimental findings show that the MF intensity sensitivity of S<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> is as high as -1.360 nm/mT at the 0° direction, and the MF direction sensitivity of S<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> is 0.4981 nm/° at 20 mT, which enhances the MF intensity and direction sensitivities of MZI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> by 6.2 times and 7.0 times. S<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> also has excellent measurement repeatability and stability. This sensor has the advantages of simple structure, easy fabrication, repeatable structure, and high economic benefits, providing a powerful solution for MF vector measurement.