Permanent magnet film magneto-optic waveguide isolator

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Abstract
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.