A guided wave optical isolator using a four layered leaky yttrium iron garnet (YIG) waveguide with a YIG guiding layer is proposed and analyzed through a transfer matrix formulation. The dependence of isolation characteristics on different waveguide parameters are discussed. It is shown that for four layered structures an isolation ratio of about 24 dB can be achieved with YIG films having large gyrotropy. It is also shown that by replacing the single guiding YIG film with multilayers of YIG with compensated walls and proper permittivity, high isolation ratio can be achieved even with currently available YIG films having low gyrotropy.
Vishnu Priye, Bishnu P. Pal, and K. Thyagarajan, "Analysis and Design of a Novel Leaky YIG Film Guided Wave Optical Isolator," J. Lightwave Technol. 16, 246- (1998)