Optical waveguide device and method of making the same

An optical waveguide device comprising:

• an optical waveguide substrate including a support, a first cladding layer disposed on the support, a core layer disposed on the first cladding layer, and a second cladding layer selectively covering the core layer;
• and
• a silicon photonic chip including a silicon substrate and a silicon waveguide disposed on one side of the silicon substrate,
• wherein part or all of a thickness of one end of the silicon waveguide in an optical waveguide direction is embedded in the core layer exposed from the second cladding layer, and is optically coupled with the core layer,
• wherein a thickness of the core layer in a place covered with the silicon substrate in plan view is less than a thickness of the core layer in a place not covered with the silicon substrate in the plan view, and
• wherein in a direction perpendicular to the optical waveguide direction, a first width of the core layer at a point of contact with the silicon substrate is wider than a second width of the core layer in a place covered with the second cladding layer.