An embodiment semiconductor optical device includes an optical waveguide including a core, and an active layer extending in the waveguide direction of the optical waveguide for a predetermined distance and arranged in a state in which the active layer can be optically coupled to the core. The core and the active layer are arranged in contact with each other. The core is formed of a material with a refractive index of about 1.5 to 2.2, such as SiN, for example. In addition, the core is formed to a thickness at which a higher-order mode appears. The higher-order mode is an E.sub.12 mode, for example.

A light emitting device according to an embodiment of the present disclosure includes: a semi-insulating substrate; a semiconductor layer; a semiconductor stacked body; a buried layer; and a non-continuous lattice plane. The semi-insulating substrate has a first surface and a second surface that are opposed to each other. The semiconductor layer is stacked on the first surface of the semi-insulating substrate. The semiconductor layer has electrical conductivity. The semiconductor stacked body is stacked above the first surface of the semi-insulating substrate with the semiconductor layer interposed in between. The semiconductor stacked body has a light emitting region and includes a ridge section on the semi-insulating substrate side. The light emitting region is configured to emit laser light. The buried layer is provided around the ridge section of the semiconductor stacked body. The non-continuous lattice plane is provided between the semi-insulating substrate and the semiconductor stacked body.

A light emitting device according to an embodiment of the present disclosure includes: a semi-insulating substrate; a semiconductor layer; a semiconductor stacked body; a buried layer; and a non-continuous lattice plane. The semi-insulating substrate has a first surface and a second surface that are opposed to each other. The semiconductor layer is stacked on the first surface of the semi-insulating substrate. The semiconductor layer has electrical conductivity. The semiconductor stacked body is stacked above the first surface of the semi-insulating substrate with the semiconductor layer interposed in between. The semiconductor stacked body has a light emitting region and includes a ridge section on the semi-insulating substrate side. The light emitting region is configured to emit laser light. The buried layer is provided around the ridge section of the semiconductor stacked body. The non-continuous lattice plane is provided between the semi-insulating substrate and the semiconductor stacked body.

Various semiconductor laser and optical amplifier designs and injection current control methods are disclosed that enable tailoring a distribution of the injection current along an active waveguide of the laser or the optical amplifier. Such configurations can be used to reduce longitudinal current crowding along the active waveguide of the laser or the optical amplifier. The electrodes and/or one or more layers of the laser or the optical amplifier may be segmented to provide a tailored longitudinal injection current distribution.

A laser structure may include a substrate, an active region arranged on the substrate, and a waveguide arranged on the active region. The waveguide may include a first surface and a second surface that join to form a first angle relative to the active region. A material may be deposited on the first surface and the second surface of the waveguide.

A quantum-cascade laser element includes: an embedding layer including a first portion formed on a side surface of a ridge portion, and a second portion extending from an edge portion of the first portion along a width direction of a semiconductor substrate; and a metal layer formed at least on a top surface of the ridge portion and on the first portion. A surface of the first portion has a first inclined surface inclined with respect to the side surface to go away from the side surface as going away from the semiconductor substrate, and a second inclined surface located opposite to the semiconductor substrate with respect to the first inclined surface and inclined with respect to a center line to approach the center line as going away from the semiconductor substrate. The metal layer extends over the first inclined surface and the second inclined surface.

A quantum-cascade laser element includes: an embedding layer including a first portion formed on a side surface of a ridge portion, and a second portion extending from an edge portion of the first portion along a width direction of a semiconductor substrate; and a metal layer formed at least on a top surface of the ridge portion and on the first portion. A surface of the first portion has a first inclined surface inclined with respect to the side surface to go away from the side surface as going away from the semiconductor substrate, and a second inclined surface located opposite to the semiconductor substrate with respect to the first inclined surface and inclined with respect to a center line to approach the center line as going away from the semiconductor substrate. The metal layer extends over the first inclined surface and the second inclined surface.

A light-emitting element includes a mesa structure in which a first compound semiconductor layer of a first conductivity type, an active layer, and a second compound semiconductor layer of a second conductivity type are disposed in that order, wherein at least one of the first compound semiconductor layer and the second compound semiconductor layer has a current constriction region surrounded by an insulation region extending inward from a sidewall portion of the mesa structure; a wall structure disposed so as to surround the mesa structure; at least one bridge structure connecting the mesa structure and the wall structure, the wall structure and the bridge structure each having the same layer structure as the portion of the mesa structure in which the insulation region is provided; a first electrode; and a second electrode disposed on a top face of the wall structure.

A semiconductor optical device includes: a lower mesa structure extending in a stripe shape and composed of some layers including an active layer; a buried layer configured to bury both sides of the lower mesa structure and made of indium phosphide; and an upper mesa structure extending in a stripe shape and composed of some layers including a bottom layer made of phosphorus-free materials, the bottom layer having a bottom surface protruding from a topmost layer of the lower mesa structure, the bottom surface being in contact with the lower mesa structure and the buried layer.

A semiconductor optical device includes: a lower mesa structure extending in a stripe shape and composed of some layers including an active layer; a buried layer configured to bury both sides of the lower mesa structure and made of indium phosphide; and an upper mesa structure extending in a stripe shape and composed of some layers including a bottom layer made of phosphorus-free materials, the bottom layer having a bottom surface protruding from a topmost layer of the lower mesa structure, the bottom surface being in contact with the lower mesa structure and the buried layer.