Abstract: An optical semiconductor device includes: a base including a surface intersecting with a first direction; a mesa protruding from the surface in the first direction, including a top surface and two side surfaces, and extending along the surface in a direction intersecting the first direction; and a heater layer including a top wall positioned on a side opposite to the base with respect to the top surface, the heater layer extending along the mesa, the mesa including a first mesa extending in a second direction intersecting the first direction, and a plurality of second mesas branching from the first mesa and extending so as to be away from each other in a third direction toward the second direction from the first mesa, the third direction intersecting both of the first direction and the second direction.

Abstract: A semiconductor laser device includes: a main body including a first layer having n-type conductivity, a second layer having p-type conductivity, and an active layer interposed between the first layer and the second layer, the first layer, the second layer, and the active layer being laminated in a lamination direction; a front-side mirror formed on a front facet of the main body, the front facet being parallel to the lamination direction; and a rear-side mirror formed on a rear facet of the main body, the rear facet facing the front facet in an optical waveguide direction that crosses the lamination direction and the front facet. The first layer includes an electric field control layer having a shorter composition wavelength than an emission wavelength of the active layer. The second layer includes an optical guide layer having a shorter composition wavelength than the emission wavelength of the active layer.

Abstract: A semiconductor device includes: a base including a base surface; a mesa protruding from the base surface in a first direction intersecting the base surface, the mesa including a top surface and two side surfaces on both sides of the top surface, and extending along the base surface; and an electric resistor including a top wall provided on the top surface and a side wall provided on at least one of the two side surfaces, the electric resistor being configured such that a current flows in an extending direction of the mesa.

Abstract: A semiconductor device includes: a mesa portion that has a semiconductor layered structure, and that extends in a predetermined direction; an extending portion that extends along the mesa portion and that is separated by trench grooves arranged respectively on both sides of the mesa portion; insulating portions that are made from an insulating material, and are arranged in the respective trench grooves; and a conductive portion that is arranged on an upper side of the mesa portion. Further, at least one of the insulating portions adheres intimately to the mesa portion, and forms a gap between the at least one of the insulating portions and the extending portion in at least a part of an extending direction of the mesa portion, and the conductive portion is arranged across at least one of the insulating portions and the mesa portion.

Abstract: A semiconductor laser includes a semiconductor substrate, an active region provided over the semiconductor substrate and having an active layer and a first diffraction grating, and a guiding region provided over the semiconductor substrate and having a guiding layer continuously extending from the active layer in an optical axis direction and a second diffraction grating continuously extending from the first diffraction grating in the optical axis direction. A grating period of the second diffraction grating is uniform, the first diffraction grating has a first part in which a grating period becomes uneven, and a grating formation density of the first diffraction grating is smaller than the grating formation density of the second diffraction grating.

Abstract: A semiconductor laser includes a semiconductor substrate, an active region provided over the semiconductor substrate and having an active layer and a first diffraction grating, and a guiding region provided over the semiconductor substrate and having a guiding layer continuously extending from the active layer in an optical axis direction and a second diffraction grating continuously extending from the first diffraction grating in the optical axis direction. A grating period of the second diffraction grating is uniform, the first diffraction grating has a first part in which a grating period becomes uneven, and a grating formation density of the first diffraction grating is smaller than the grating formation density of the second diffraction grating.