DyBi Garnet Films with Improved Temperature Dependence of Faraday Rotation

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)3 Fe5 O12 (R = Dy, Gd, Yb) and (GdBi)3 (FeAlGa)5 O12 films in the 1.3 and 1.5 ¿m wavelength bands. Among the various compositions of Bi-substituted garnet films examined, the Dy2.5 Bi0.5 Fe5 O12 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 Y3 Fe5 O12 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.