OPTICAL SEMICONDUCTOR DEVICE, OPTICAL INTEGRATED DEVICE, AND MANUFACTURING METHOD FOR OPTICAL SEMICONDUCTOR DEVICE

An optical semiconductor device includes: a substrate; a first protrusion protruding from the substrate in a first direction and including a first mesa having a laminate structure in which a plurality of semiconductor layers are layered on the substrate in the first direction, the first mesa including an active layer as one of the semiconductor layers; and a second protrusion protruding from the substrate in the first direction at a distance from the first protrusion in a second direction intersecting with the first direction, the second protrusion having a same laminate structure as the laminate structure of the first mesa, wherein one of the plurality of semiconductor layers is exposed at an end portion of the second protrusion in the first direction.