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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