Highly sensitive Mach-Zehnder interferometric micromagnetic field sensor based on 3D printing technology.

A two-photon 3D printed polymer magnetic sensing device based on a Mach-Zehnder interferometer (MZI) is proposed. One arm of the MZI contains a hollow cavity and two connecting open channels that can be filled with magnetic fluids (MFs) and sealed by the UV curable adhesive, forming a magneto-optical component of the interferometer. As the magnetic field changes, the refractive index (RI) of the MF changes, and the effective RI of the guiding mode of the waveguide changes accordingly, which results in a change in the phase of the MZI. The interferometric spectra can be used to evaluate the sensing sensitivity. The MZI structure with a hollow length of 40 µm is fabricated, and the microstructure is encapsulated with MF, demonstrating a highly sensitive magnetic field device. The experimental results show that the magnetic field sensitivity of the fabricated magnetic field device is -1.675/. For a spectrometer with a resolution of 1 pm, the minimal detectable magnetic field resolution of the sensor is up to 59.7 nT with good stability.