| 摘要 |
An optical waveguide of the invention is formed by depositing an underclad on a silicon substrate, by forming thereon a core having, for instance, an arrayed waveguide grating circuit, and by covering the core with an overclad, and, without disposing a half wave plate, can suppress an influence of polarization dependency attenuation and deterioration due to moisture absorption. An arrayed waveguide grating circuit includes at least one input waveguide, a first slab waveguide, an arrayed waveguide made of a plurality of channel waveguides arranged side by side with lengths different by a predetermined amount from each other, a second slab waveguide, and an output waveguide. The clad and the core are made of silica-based glass. When the thermal expansion coefficient of the substrate is alphas, that of the underclad alphauc, and that of the overclad alphaoc, alphaoc is equal to or greater than (alphas-2.0x10-7) and equal to or smaller than (alphas2.0x10-7), and (alphaoc-alphauc) is equal to or smaller than (21.5x10-7).
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