Magneto-optical materials and designs for integrated TE- and TM-mode planar waveguide isolators: a review [Invited]

Optical isolators are unidirectional devices that employ the magneto-optical (MO) property of iron garnets to block the reflected light in almost all optical systems. Sputter deposition of either doped yttrium iron garnets (YIG) with seed-layers or seed-layer free terbium iron garnets (TIG) will help realize integrated planar isolators. Faraday rotation waveguides are designed as a viable solution to enable these monolithically integrated garnets to overcome the limitations inherent to hybrid integration of interferometric devices. In fact, small footprint Faraday rotation devices have been achieved using doped TIG for both TE/TM modes with sufficiently low loss and large isolation ratios.