| 摘要 |
PURPOSE: To provide an optical waveguide such as an array waveguide type diffraction grating or the like in which the influence of polarized wave dependency loss is suppressed without providing a half-wave length plate and the deterioration due to moisture absorption is suppressed. CONSTITUTION: An underclad is formed on a silicon substrate 11, on which a plurality of optical input waveguides 12, a first slab waveguide 13, an array waveguide 14 which is composed of a plurality of parallel channel waveguides 14a of which set lengths are different from one another, a second slab waveguide 15 and an optical output waveguide 16 are formed with core, and the core is covered with an overclad. The clad and the core are formed with quartz-based glass and the following relations are satisfied αs-2.0x10¬-7<=αoc<=αs+2.0x10¬-7 and αoc-αuc<=21.5x10¬-7, where αuc stands for the thermal expansion coefficient of the underclad, αs stands for the thermal expansion coefficient of the substrate 11 and αoc stands for the thermal expansion coefficient of the overclad.
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