Effects Of Magnetically Induced Optical Incoherence In Arrayed Faraday Rotator Crystals

Bismuth doped iron garnet films were studied in arrayed structures to improve sensitivity in polarimetric magnetic field sensors. The sensitivity gained from the arrayed configuration was found to depend on the ferromagnetic domain geometry of the films. Under small, externally applied fields, films with planar anisotropy yielded an optical modulation depth which increased linearly with the number of crystals in the array. In films with perpendicular anisotropy, linearity and sensitivity were obstructed by a mechanism of optical polarization incoherence which was found to be generated within the magnetic domains. Our results indicate that optimal sensitivity in arrayed configurations requires planar anisotropies, or a direction of laser propagation that is perpendicular to the local domain magnetization.