Fabrication processes of a magneto-optic waveguide with a Si guiding layer for an optical isolator employing a nonreciprocal guided-radiation mode conversion are investigated. The optical isolator is constructed on a silicon-on-insulator (SOI) structure. The magneto-optic waveguide is fabricated by bonding the Si guiding layer with a cerium-substituted yttrium iron garnet (Ce:YIG). The relationship of waveguide geometric parameters is determined at a wavelength of 1550 nm. The results show that larger tolerance for isolator operation can be obtained at smaller gaps between Si and Ce:YIG. Bonding processes including photosensitive adhesive bonding and surface activated bonding are then compared. It is found that the surface activated bonding process is easier to control and more promising than the photosensitive adhesive bonding.

A photosensitive adhesive bonding process for a magnetooptic waveguide for an optical isolator employing a nonreciprocal guided-radiation mode conversion is investigated at 1.55 µm. The magnetooptic waveguide is a straight rib type, and it is fabricated by bonding the Si guiding layer to a magnetic garnet. In the fabrication process, an adhesive material is diluted to obtain a certain thickness before depositing on a silicon-on-insulator (SOI) substrate. The relationship between the percent dilution ratio and the thickness of the adhesive layer is considered. The smallest gap thickness is found to be 0.66 µm at a dilution ratio of 2%.

The temperature dependence of the optical isolator employing a nonreciprocal guided-radiation mode conversion is investigated. The optical isolator consists of a rib-type magnetooptic waveguide with an amorphous Si (a-Si:H) guiding layer. The nonreciprocal phase shift in the optical isolator is calculated at a wavelength of 1.55 µm. The relationship of rib height and rib width for the isolator operation is clarified for various operating temperatures. Refractive indices of layers in the magnetooptic waveguide are considered since proper refractive indices can circumvent waveguide parameter deviation due to the temperature shift. The results show that athermal operation can be achieved by the negative temperature dependence of the refractive index of the upper cladding layer, and the relationship of waveguide parameters varies only slightly with the selected upper cladding layer.

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