Development of Highly Accurate Optical Magnetic Field Sensors

Abstract

We developed highly accurate optical magnetic field sensors. The sensor optical system has a confocal optical system using ball lenses. Bi-substituted rare earth iron garnets were prepared by the LPE method for use as Faraday rotators. We found that a new garnet composition, Bi_1.14Gd_0.57La_0.02Y_1.27Fe_4.53Ga_0.47O_12, showed stable temperature characteristics of the sensitivity; The temperature dependence of the sensor output was less than 2.0% from -20°C to +80°C. We also improved the linearity error in the small magnetic field by using the film thickness dependence of the wall coercive force. The linearity error of the sensor output was within 1.0% for alternating magnetic fields from 3.0 Oe to 420 Oe. The sensors achieved high performance with regard to the linearity and the temperature characteristics.