A semiconductor laser diode includes a semiconductor substrate, a laser portion that is provided on the semiconductor substrate and has an active layer, and an optical modulation portion that is provided on the semiconductor substrate and has a light absorption layer configured to absorb laser light from the laser portion. In the semiconductor laser diode, the light absorption layer includes a first light absorption layer and a second light absorption layer. The active layer, the first light absorption layer, and the second light absorption layer are arranged in this order in a light guiding direction. The first light absorption layer has a first wavelength obtained by photoluminescence measurement, the second light absorption layer has a second wavelength obtained by photoluminescence measurement, and the second wavelength is longer than the first wavelength.

A quantum cascade semiconductor laser includes a laser structure having a first area including an end face, a second area, and a third area; a metal layer provided on a major surface in the third area; a separation area provided on the major surface; and a reflector provided on the laser structure. The reflector includes a dielectric film and a metal reflecting film provided on the end face and the separation area. The separation area has a first portion, a second portion, and a third portion. The metal layer has an edge separated from the end face in the third area. The contact layer has an edge separated from the end face in the third area. The first portion projects more than the second portion over the semiconductor mesa. The third portion projects more than the second portion over the semiconductor mesa.

A semiconductor integrated optical device includes a waveguide mesa having a first multilayer including a first core layer, a second multilayer including a second core layer, and a butt joint interface between the first core layer and the second core layer; a support having first to third regions; and a buried semiconductor region provided on the support. The first multilayer has a first mesa width on the first region. The second multilayer has a second mesa width on the second region. On the third region, the second multilayer has a waveguide portion having a third mesa width smaller than the first and the second mesa widths. The second core layer has a waveguide core thickness on the second region. In the waveguide portion, the second core layer has a core portion having a thickness different from the waveguide core thickness at a position away from the butt-joint interface.

A quantum cascade laser includes a laser structure having an output face for emitting laser light in a first direction; and a lens having an entrance surface and a convex surface, the entrance surface receiving the laser light from the output face, and the convex surface emitting the laser light after being condensed by the lens. The laser structure includes a semiconductor substrate and a mesa waveguide provided on a first region of a principal surface of the semiconductor substrate, the mesa waveguide extending in the first direction. The lens includes a semiconductor and is provided on a second region of the principal surface of the semiconductor substrate. The first region and the second region are arranged in the first direction.

A quantum cascade laser includes a laser structure having an output face for emitting laser light in a first direction, and a reflecting film provided on the output face. The laser structure includes a core layer. The output face includes an end face of the core layer. The end face includes a first region and a second region that differs from the first region. The reflecting film covers the first region and does not cover the second region.

A semiconductor laser includes a semiconductor layer including end faces and at least one of the end faces is configured as a light emission end face. The semiconductor layer includes a waveguide and a light window structure region. The waveguide has a first width and is extended between the end faces. The light window structure region includes an opening having a second width greater than the first width arranged along the waveguide and is formed continuously or intermittently from one to another of the end faces.

A semiconductor light-emitting device includes a stacked body, a cutout section, and a high-resistance region. The stacked body includes a first conductive-type semiconductor layer, an active layer, and a second conductive-type semiconductor layer in this order and has paired side faces opposed to each other. The cutout section is provided on at least one of the paired side faces of the stacked body and has a bottom face where the first conductive-type semiconductor layer is exposed. The high-resistance region is provided from the vicinity of the bottom face of the cutout section to the side face of the stacked body and has electric resistance higher than the electric resistance of the stacked body in a periphery of the high-resistance region.

What is provided are: an active-layer ridge which is composed of an n-type cladding layer, an active layer, a first p-type cladding layer and a second n-type blocking layer that are stacked in this order on an n-type InP substrate, and which is formed to project from a position lower than the active layer; burying layers by which both side portions of the active-layer ridge are buried up to a position higher than the active layer; first n-type blocking layers which are each stacked on a front-surface side of each of the burying layers, to be placed on the both sides of the ridge; and a second p-type cladding layer by which an end portion of the active-layer ridge and the first n-type blocking layers are buried thereunder; wherein a current narrowing window for allowing a hole current to pass therethrough is provided in and at a center of the second n-type blocking layer placed at a top of the active-layer ridge.

A semiconductor optical device may include a semiconductor substrate; a mesa stripe structure that extends in a stripe shape in a first direction on the semiconductor substrate and includes a contact layer on a top layer; an adjacent layer on the semiconductor substrate and adjacent to the mesa stripe structure in a second direction orthogonal to the first direction; a passivation film that covers at least a part of the adjacent layer; a resin layer on the passivation film; an electrode that is electrically connected to the contact layer and extends continuously from the contact layer to the resin layer; and an inorganic insulating film that extends continuously from the resin layer to the passivation film under the electrode, is spaced apart from the mesa stripe structure, and is completely interposed between the electrode and the resin layer.

A buried semiconductor optical device comprises a semiconductor substrate; a mesa-stripe portion including a multi-quantum well layer on the semiconductor substrate; a buried layer consisting of a first portion and a second portion, the first portion covering one side of the mesa-stripe portion, the second portion covering the other side of the mesa-stripe portion, and the first portion and the second portion covering a surface of the semiconductor substrate; and an electrode configured to cause an electric current to flow through the mesa-stripe portion, the buried layer comprising, from the surface of the semiconductor substrate, a first sublayer, a second sublayer, and a third sublayer, the first sublayer, the second sublayer, and the third sublayer each consisting of semi-insulating InP, the first sublayer and the second sublayer forming a pair structure, the second sublayer being located above the multi-quantum well layer from the surface of the semiconductor substrate, and the second sublayer consisting of one or more layers selected from a group of InGaAs, InAAs, InGaAAs, InGaAsP, and InAlAsP.