Buried channel waveguides in magneto-optic yttrium iron garnet have been prepared for application to waveguide isolators. The channel waveguides are fabricated in a three-step procedure: planar single-mode waveguides are grown, then rib waveguides are wet-etched into the planar waveguides and successively overgrown with top cladding. Light propagation and mode conversion characteristics of such waveguides have been investigated.
"Buried Channel Waveguides In Magneto-Optic Materials", Proc. SPIE 1018, Electro-Optic and Magneto-Optic Materials, (31 January 1989); doi: 10.1117/12.950007; https://doi.org/10.1117/12.950007