Semiconductor optical device and method of manufacturing semiconductor optical device

A semiconductor optical device comprising:

• a base configured to intersect with a first direction;
• a first protrusion configured to protrude from the base in the first direction, the first protrusion including a planar lightwave circuit including:
• a core layer;
• and a cladding layer surrounding the core layer;
• two second protrusions each configured to protrude from the base in the first direction and arranged along the first protrusion in a second direction intersecting with the first direction, a height of each second protrusion from the base in the first direction being lower than a height of the first protrusion;
• an optical semiconductor element placed on a facet of the second protrusion in the first direction and optically connected to the core layer;
• a marker provided on the second protrusion in a manner exposed on the facet of the second protrusion, the marker being made of a same material as the core layer;
• a first electrode provided to a facet of the optical semiconductor element in a direction opposite to the first direction, the first electrode positioned between the two second protrusions;
• a conductor positioned between the two second protrusions and electrically connected to the first electrode, wherein the conductor is a conductive paste,
• a rough surface configured to contact the conductive paste and having a greater surface roughness than a remaining part, the rough surface being provided at a position between the two second protrusions on the facet of the base in the first direction;
• a third protrusion configured to protrude from a position between the two second protrusions of the base in the first direction, a height of the third protrusion from the base in the first direction being lower than heights of the two second protrusions;
• and
• a third electrode provided on a facet of the third protrusion in the first direction and electrically connected to the conductor.