A semiconductor optical element is configured to emit or absorb light and includes a lower structure that includes a multiple quantum well layer; an upper mesa structure that is disposed on the lower structure; a current injection structure that is disposed on the upper mesa structure, when seen from an optical axis of the emitted or absorbed light, a width of a portion of the current injection structure in contact with the upper mesa structure is smaller than a width of the upper mesa structure, the portion of the current injection structure in contact with the upper mesa structure consisting of InP, and an average refractive index of the upper mesa structure is higher than a refractive index of the InP forming the current injection structure; and an insulating film covering both side surfaces of the upper mesa structure and a part of an upper surface of the upper mesa structure.

A semiconductor optical device is provided with a semiconductor substrate that has a length and width, a laser section that is provided on the semiconductor substrate and includes an active layer and an optical waveguide section that is provided adjacent to the laser section on the semiconductor substrate and is joined to the laser section. The optical waveguide section includes a core layer that is connected to an end portion of the active layer, and a pair of cladding layers between which the core layer is sandwiched and emits, from an emission end surface, light incident from the joining interface between the optical waveguide section and the laser section. The semiconductor optical device may be also provided with a reflection suppression layer that is provided on the upper surface of the optical waveguide section.

A semiconductor laser in which a PD unit monitoring an optical output is integrated is provided. A semiconductor laser (100) includes: a DFB unit including a back surface side first cladding layer (3), a first diffraction grating layer (9), a light emitting layer (1) having a first MQW structure and emitting a laser beam, a front surface side first cladding layer (6), and a first contact layer (12) which are stacked; a DBR unit including a back surface side second cladding layer (4) having a resistivity higher than that of the back surface side first cladding layer (3), a second diffraction grating layer (10) reflecting part of the laser beam toward the DFB unit, a first core layer (2a) guiding a remnant of the laser beam and having an effective bandgap energy smaller than that of the first MQW structure, and a front surface side second cladding layer (7) having a resistivity higher than that of the front surface side first cladding layer (6) which are stacked; and a PD unit including a back surface side third cladding layer (5), a second core layer (2b) having a second MQW structure absorbing the remnant of the laser beam guided by the first core layer (2a), a front surface side third cladding layer (8), and a second contact layer (14) which are stacked.

A quantum cascade laser includes a laser structure including a semiconductor stack and a semiconductor support, the laser structure having a first end face and a second end face opposite the first end face. The semiconductor stack is disposed on the semiconductor support. The laser structure includes a semiconductor mesa and a buried region, the semiconductor mesa including a core layer, and the buried region embedding the semiconductor mesa. The laser structure includes a first region, a second region, and a third region. The third region is provided between the first region and the second region. The first region includes the first end face. The semiconductor mesa includes a first stripe portion, a second stripe portion, and a first tapered portion, respectively, in the first region, the second region, and the third region. The first stripe portion and the second stripe portion have different mesa widths.

A method for manufacturing a monolithically integrated semiconductor optical integrated element comprising a DFB laser, an EA modulator, and a SOA disposed in a light emitting direction, comprising the step of forming a semiconductor wafer on which the elements are two-dimensionally arrayed and aligned the optical axes; cleaving the semiconductor wafer along a plane orthogonal to the light emitting direction to form a semiconductor bar including a plurality of the elements arranged one-dimensionally along a direction orthogonal to the light emitting direction such that the elements adjacent to each other share an identical cleavage end face as a light emission surface; inspecting the semiconductor bar by driving the SOA and the DFB laser through a connection wiring part together; and separating out the semiconductor bar after the inspection to cut the connection wiring part connecting the electrode of the SOA and the DFB laser to isolate from each other.

A semiconductor laser device includes a laser section and a modulator section. The laser section has: a first mesa stripe which is formed on a semiconductor substrate; semi-insulative burying layers which are placed to abut on both side surfaces of the first mesa stripe and are formed on the semiconductor substrate; n-type burying layers formed on respective surfaces of the semi-insulative burying layers; and a p-type cladding layer which covers surfaces of the n-type burying layers and the first mesa stripe. The modulator section has: a second mesa stripe which is formed on the semiconductor substrate; semi-insulative burying layers which are placed to abut on both side surfaces of the second mesa stripe and are formed on the semiconductor substrate; and a p-type cladding layer which covers surfaces of the semi-insulative burying layers and the second mesa stripe.

A semiconductor device includes a first pair of nitride semiconductor regions, and a current confinement region which includes a first portion, a second portion disposed on a side of the first portion, and a third portion disposed on another side of the first portion. A width of the second portion is larger than a width of the first portion, the width of the second portion is larger than a width between the first pair of nitride semiconductor regions, and both ends of the second portion are covered by the first pair of nitride semiconductor regions, respectively.

A method includes obtaining a semiconductor wafer having an orientation in a plane; depositing one or more masks to a semiconductor wafer, wherein each mask is configured to cover a portion of the semiconductor wafer, and wherein each mask includes a perimeter having multiple sides that are substantially aligned along a preferred crystal direction relative to the orientation that provides reduced or enhanced growth enhancement at edges of the substantially aligned sides; and performing Selective Area Epitaxy (SAE) growth on a surface of the semiconductor wafer, wherein the one or more masks inhibit the SAE growth over the associated portion.

A photonic integrated circuit including a photonic device and a gain element, said gain element formed by a process including: depositing by epitaxy a first doped layer onto a substrate; depositing by epitaxy an active layer capable of optical gain onto the first doped layer; depositing by epitaxy a second doped layer onto the active layer; pattern etching at least the second doped layer and the active layer to form a first ridge; and depositing by epitaxy a current blocking layer laterally adjacent to the first ridge at least partially filling the volume of active layer that was removed by the pattern etching; wherein the current blocking layer forms a portion of the photonic device.

A photonic integrated circuit including a photonic device and a gain element, said gain element formed by a process including: depositing by epitaxy a first doped layer onto a substrate; depositing by epitaxy an active layer capable of optical gain onto the first doped layer; depositing by epitaxy a second doped layer onto the active layer; pattern etching at least the second doped layer and the active layer to form a first ridge; and depositing by epitaxy a current blocking layer laterally adjacent to the first ridge at least partially filling the volume of active layer that was removed by the pattern etching; wherein the current blocking layer forms a portion of the photonic device.