Magnetic field vector detection at the millitesla level using a YIG microcavity optical sensor

Millitesla-level magnetic field vector detection based on a yttrium iron garnet (YIG) microcavity optical sensor with a quality factor of ∼10⁵ is proposed and demonstrated. The sensor leverages external magnetic field variations to change the dielectric constant of the material, thereby achieving refractive index sensing. The spectrum of YIG microcavities with different crystal orientations exhibits redshift with increasing magnetic field strength, reaching a maximum intensity sensitivity of approximately 0.357 pm/mT and a saturation magnetic field strength of around 45 mT. Additionally, the sensor enables 360° magnetic field direction rotation detection, with a maximum directional sensitivity of 0.132 pm/rad. The optical sensor has a small footprint, a simple structure, and a wide measurement range.