Optical waveguide device

An optical waveguide device comprising:

• a first waveguide;
• and
• a second waveguide disposed on the first waveguide,
• wherein the first waveguide includes:
• a lower cladding layer;
• a first core disposed on the lower cladding layer;
• and
• an upper cladding layer disposed on the lower cladding layer and covering the first core,
• wherein the upper cladding layer includes:
• a first surface on which the second waveguide is disposed;
• a second surface located closer to the lower cladding layer than the first surface in cross-sectional view and overlapping with the first core in plan view;
• and
• one or more recesses located between the first surface and the second surface in plan view and recessed relative to the second surface in cross-sectional view, and
• wherein the second waveguide includes a second core and a third cladding layer covering the second core,
• an edge area of a lower surface of the third cladding layer is in contact with the first surface,
• a region of the third cladding layer where the second core resides is located on the second surface via an adhesive layer, and
• the second core overlaps with the first core in plan view and is optically coupled to the first core.