Preparation of Substituted Y3Fe5O12 Waveguide Directional Coupler Using Ion-Beam Etching

The rib waveguide directional coupler of an epitaxially grown 4-µm-thick substituted Y3Fe5O12 (YIG) monolayer film on a [111]-oriented Gd3Ga5O12 (GGG) substrate is prepared by argon ion-beam etching. A Ta/organic layer double-layer mask is utilized during ion-beam etching. The basic operation of the directional coupler at λ=1.55 µm is demonstrated.