Optical Propagation and Conversion Properties of Hybrid Modes in Gyrotropic YIG Film Waveguides with Anisotropic Crystal Cover Layers

The dispersion and field distribution properties of hybrid eigen modes in gyrotropic YIG thin-film waveguides with GGG substrates and anisotropic crystal covers are precisely studied for their application to nonreciprocal devices such as optical film isolators. Phase matching and strong coupling conditions due to anisotropic top layers on gyrotropic films are derived for two independent fundamental hybrid modes. It is found that the nonreciprocal thin film waveguides of 50 percent mode conversion necessary for constructing optical isolators can be achieved using LiIO 3 crystals and YIG films of thickness 0.36 µm on GGG substrates of length 0.5 mm.