Optical semiconductor device, optical unit, and method for manufacturing optical unit

An optical unit, comprising:

• an optical semiconductor device, comprising:
• a semiconductor substrate including a first main surface and a second main surface on a side opposite to the first main surface;
• a stacked body that is formed on the first main surface and includes an active layer and a contact layer arranged on a side opposite to the semiconductor substrate with respect to the active layer;
• a first electrode in contact with the contact layer;
• and
• a second electrode formed on the second main surface, wherein the stacked body includes a light transmitting portion formed by not covering at least part of a surface of the contact layer on a side opposite to the semiconductor substrate with the first electrode;
• a third electrode;
• and
• a waveguide member formed of one or more semiconductor materials and in optical contact with the light transmitting portion,
• wherein the optical semiconductor device is configured such that a waveguide mode is not formed by current application within a predetermined range through the first electrode and the second electrode in a state in which the light transmitting portion is not in optical contact with the waveguide member, and a waveguide mode is formed by the current application within the predetermined range through the first electrode, the second electrode, and the third electrode in a state in which the light transmitting portion is in optical contact with the waveguide member,
• wherein the first electrode is electrically connected to the third electrode via solder, and
• wherein a thickness of the waveguide member in a direction perpendicular to the first main surface is smaller than a thickness of the solder in the direction perpendicular to the first main surface.