Optical Propagation Properties in Gyromagnetic Waveguides Using Faraday Effects of YIG Thin Films on GGG Substrates

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Abstract
A theoretical analysis using hybrid modes is presented for gyromagnetic thin film waveguides consisting of YIG crystal films on the GGG substrates, to obtain accurate design data for nonreciprocal circuits of optical isolators. In this hybrid mode method, eigen HE and EH modes which are the exact solutions of electromagnetic fields in garnet films are shown. Expressions for the eigen functions in terms of the dielectric tensor elements with the Faraday effect are derived. To estimate the fundamental propagation properties of optical hybrid waves, propagation constants and wave function profiles for hybrid modes are evaluated in a lossless YIG thin film on the GGG substrate. TE-TM mode conversions through the Faraday effect are evaluated in devices consisting of two isotropic waveguides and one gyromagnetic waveguide with the isotropic exterior substrates of upper cover sides that yield the phase mismatch condition.