Permanent magnet film magneto-optic waveguide isolator

Recent advances in high-coercivity planar-magnetization film magnets and Bi-YIG (bismuth-substituted yttrium iron garnet) film technology have opened up the possibility of fabricating very small magneto-optic devices. In this article we demonstrate that these two technologies can be brought together to fabricate a high performance waveguide magneto-optic isolator for use in integrated optical circuits. The device operates at 1.55-μm wavelength and consists of a waveguide etched into a Bi-YIG film whose magnetization is saturated by a 22-μm-thick TbCu7-type SmCo magnet with a coercivity of 4 kOe. Isolation ratios of 25 dB have been obtained in the wavelength region between 1490 and 1555 nm.