Development of an Optical Probe Current Sensor for Local and Narrow Area Measurement Using Magnetic Domain Reversal in Bismuth-Substituted Rare-Earth Iron Garnet Crystal

In this article we have developed an optical probe electric current sensor using a Faraday effect of granular magnetic film as a new current sensor to replace a current transformer and a Rogowski coil. However, the sensitivity for small current fields in the previously developed sensor was low, and the signal was buried in the floor noise, making accurate measurement impossible. In this study, we investigated a sensor using magnetic domain reversal of Bismuth-substituted rare-earth iron garnet (Bi:RIG) crystal for Faraday element to solve the previous problem and succeeded in developing a sensor with excellent linearity and a high signal-to-noise ratio by optimizing the Bi:RIG crystal thickness and the light-beam diameter to be irradiated.