Abstract

Optical isolators and circulators are realized utilizing 45° Faraday rotation ^1,2). Pure or substituted yttrium iron garnet (YIG) film is used in infrared optical communications, because of its transparency and large Faraday effect. Substituted YIG film is grown by liquid phase epitaxy (LPE). In general, it has uniaxial magnetic anisotropy with its easy magnetization axis parallel to its substrate. Small planar magnets can provide sufficient in plane magnetization. However, large external magnetic fields are needed to attain perpendicular magnetization. Bulky cylindrical magnets are attached to conventional Faraday rotators, because the light travels in a direction perpendicular to their substrates. It is difficult to construct waveguides that are perpendicular to the surface. It is easy, with a planar structure, to grow undercladding, core and overcladding layers onsubstrates ³⁾. The required film thicknesses are several 100 μm for a perpendicular structure and several 10 μm for a planar one. The planar structure allows not only the easy fabrication of Faraday rotators but also the compact integration of external magnetic circuits and magneto-optic waveguides into optical circuits.

© 1995 Optical Society of America