| 摘要 |
Provided are an optical waveguide and a production method thereof which can constrict both the width and thickness of the SOI optical waveguide core layer in the same process and at the same time, simplify production process, and reduce optical losses. An optical waveguide includes a first clad layer formed on a semiconductor substrate; a first core layer formed on the upper side of the first clad layer with the use of a semiconductor material the refractive index of which is higher than that of the first clad layer; and a second clad layer formed on the upper side of the first core layer with the use of a material the refractive index of which is lower than that of the first core layer. The width of the first core layer is defined based on the width of an unoxidized semiconductor material sandwiched between oxide films the parts of which are thermally oxidized. The thickness of the first core layer is defined based on the thickness of an unoxidized semiconductor material sandwiched between the first clad layer and an oxide film the part of which is thermally oxidized. At least the input/output portion of the optical waveguide has a tapered waveguide portion where the width and thickness of the first core layer monotonically decreases or increases with respect to the propagation direction of light.
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