Highly accurate optical magnetic-field probe sensors that use iron garnet films have been developed. New probe-type sensors were designed with a confocal optical system. A new garnet composition, Bi<sub>0.98</sub>Gd<sub>0.92</sub>La<sub>0.03</sub>Y<sub>1.07</sub>Fe<sub>4.72</sub>Ga<sub>0.28</sub>O<sub>12</sub>, was found that shows high temperature stability for a sensitivity of less than 2.0% from −20 to +80 °C. The linearity error of the sensor output was within 1.0% for alternating magnetic fields from 0.3 to 42 mT. An optical current transformer that uses the proposed sensor has an ac linearity of 1.0% for input current up to nearly 300 A. The sensor realized high performance in actual use.
© 1999 Optical Society of America
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(120.4570) Instrumentation, measurement, and metrology : Optical design of instruments
(160.3820) Materials : Magneto-optical materials
(230.2240) Optical devices : Faraday effect
(230.3810) Optical devices : Magneto-optic systems
Nobuki Itoh, Hisashi Minemoto, Daisuke Ishiko, and Satoshi Ishizuka, "Small Optical Magnetic-Field Sensor That Uses Rare-Earth Iron Garnet Films Based on the Faraday Effect," Appl. Opt. 38, 2047-2052 (1999)