Optical semiconductor element

An optical semiconductor element comprising:

• a substrate having a first main surface whose plane orientation is {100} and a second main surface provided opposite to the first main surface;
• and
• a first semiconductor layer provided on the first main surface and provided with a mesa,
• wherein the mesa includes a laser portion and an optical amplifier portion,
• wherein the laser portion includes
• a first surface perpendicular to the first main surface, and
• a second surface perpendicular to the first main surface and parallel to the first surface,
• wherein the optical amplifier portion includes
• a third surface perpendicular to the first main surface and contiguous with the first surface,
• a fourth surface perpendicular to the first main surface and contiguous with the second surface,
• a fifth surface perpendicular to the first main surface and contiguous with the third surface,
• a sixth surface perpendicular to the first main surface, contiguous with the fourth surface, and parallel to the fifth surface, and
• an end surface perpendicular to the first main surface, contiguous with the fifth surface and the sixth surface, and from which light is emitted,
• wherein a first distance between the first surface and the second surface is smaller than a second distance between the fifth surface and the sixth surface,
• wherein the first surface and the second surface are parallel to a {01-1} plane of the substrate,
• wherein the end surface is perpendicular to the {01-1} plane,
• wherein the third surface and the fourth surface are inclined in a same direction with respect to each other from the {01-1} plane in a plane parallel to the first main surface,
• wherein the third surface is inclined more from the {01-1} plane than the fourth surface in the plane parallel to the first main surface,
• wherein the fifth surface and the sixth surface are inclined in a same direction as the third surface and the fourth surface from the {01-1} plane in the plane parallel to the first main surface,
• wherein the optical semiconductor element comprises
• a second semiconductor layer contacting the first surface, the second surface, the third surface, the fourth surface, the fifth surface, and the sixth surface,
• a first electrode pad provided at a position where the laser portion is interposed between the substrate and the first electrode pad, including a first metal, and electrically connected to the laser portion,
• a second electrode pad provided at a position where the optical amplifier portion is interposed between the substrate and the second electrode pad, including a second metal, and electrically connected to the optical amplifier portion, and
• a third electrode pad provided at the second main surface, electrically connected to the substrate, and including a third metal,
• wherein, in plan view, on an outer side of the first electrode pad, the optical semiconductor element comprises
• a first region situated on an extension line of the laser portion on a propagation direction side of light propagating in a straight line inside the laser portion, and
• a second region overlapping the optical amplifier portion, and
• wherein a ratio of a metal film covering the first semiconductor layer or the second semiconductor layer is lower inside the first region than inside the second region.