In optical communication system, Yttrium iron garnet (Y3Fe5O12:YIG) and Bi, Ce doped YIG crystals are the commonly used magnetooptical materials of optical isolators because of its large Faraday rotation angle, high transparency, and small absorption in the wavelengths of 1.2–5.0 lm. However, as the rapid development of fiber laser systems and the optical communication technology, the demand of high quality Magneto-optical material in the visible and near-infrared region has greatly increased.