Magneto-optical properties of spin-coated bismuth-substituted yttrium iron garnet films on silicon substrates at 1550-nm wavelength

Bismuth-substituted yttrium iron garnet (Bi:YIG) films were prepared by using spin coating processes with metal-organic-decomposition-method-based solutions on crystalline silicon (Si) substrates, and their magneto-optic properties at the 1550-nm wavelength region were investigated by performing various thermal treatments. The maximum Verdet constant of the Bi1Y2Fe5O12 film on the Si substrate with a middle buffer layer of Bi2Y1 Fe5 O12 was measured to be 1 072 038°/T/m at 1550-nm wavelength in the unsaturated linear magnetization region by accounting for the negative Verdet constant of the silicon substrate. The optimum thermal treatment condition was observed at the maximum annealing temperature of 700 °C and the annealing speed of 3 °C/min. These spin coating enabled processes may be included to the conventional complementary metal-oxide semiconductor fabrication processes to demonstrate integrated optical waveguide-type isolators on silicon-on-insulator wafers.