Multiple self-mixing interference with the Faraday effect for detecting magnetic fields.

Detection of magnetic fields is widely used in magnetic materials, electronic devices, medical imaging, and navigation systems. We conducted the experiments using a TGG crystal in different magnetic fields to observe multiple laser self-mixing interference in the frequency domain for experimentation. Every spectral line of the multiple laser self-mixing interference contained the peaks exhibiting a decay trend due to the rotation of the light's polarized orientation according to the Faraday effect. The decay rate of the spectral line depended on the magnetic field density. To quantify the decay rate, the decay coefficient was obtained via fitting of the spectral line. The equation between the decay coefficient and the magnetic field density was established from the experimental results, and the magnetic field density was detected using the equation. This work exhibited a potential detection capability for magnetic fields.