DyBi Garnet Films with Improved Temperature Dependence of Faraday Rotation

Abstract

To improve the temperature dependence of the isolation value of magneto-optical Bi-substituted garnet films for use in optical isolators, the temperature dependence of the Faraday rotation coefficient was measured for (RBi) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> (R = Dy, Gd, Yb) and (GdBi) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (FeAlGa) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> films in the 1.3 and 1.5 μm wavelength bands. Among the various compositions of Bi-substituted garnet films examined, the Dy <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> films showed a 2 percent shift in Faraday rotation from that measured at 25°C and an isolation figure of 36 dB in the temperature range from 0 to 50°C. An isolation figure of 29 dB is assured even if the incident light wavelength fluctuates due to the ambient temperature and manufacturing tolerances. These values correspond to those of Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> bulk single crystals. From the viewpoint of material design, the temperature dependence of the Faraday rotation for Bi-substituted garnets is improved by employing a solid solution with a rare-earth garnet which has a positive Faraday rotation and a negative temperature coefficient of Faraday rotation at room temperature.