An optical transmission apparatus includes a first multilevel optical phase modulator and a first semiconductor optical amplifier. The first semiconductor optical amplifier includes a first active region having a first multiple quantum well structure. Assuming that a first number of layers of a plurality of first well layers is defined as n.sub.1 and a first length of the first active region is defined as L.sub.1 (μm): (a) n.sub.1=5 and 400≤L.sub.1≤563; (b) n.sub.1=6 and 336≤L.sub.1≤470; (c) n.sub.1=7 and 280≤L.sub.1≤432; (d) n.sub.1=8 and 252≤L.sub.1≤397; (e) n.sub.1=9 and 224≤L.sub.1≤351; or (f) n.sub.1=10 and 200≤L.sub.1≤297.

Structures and methods for reducing the thermal resistance of quantum cascade laser (QCL) devices and QCL-based photonic integrated circuits (QCL-PIC) are provided. In various embodiments, the native substrate of QCL and QCL-PIC devices is replaced with a foreign substrate that has very high thermal conductivity, for example, using wafer bonding methods. In some examples, wafer bonding of processed, semi-processed, or unprocessed QCL and QCL-PIC epilayers or devices on their native substrate to a high-thermal-conductivity substrate is performed, followed by removal of the native substrate via selective etching, and performing additional device processing if necessary. Thereafter, in some embodiments, cleaving or dicing individual devices from the bonded wafers may be performed, for example, for mounting onto heat sinks.

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 method of manufacturing an optical semiconductor device includes a step of forming semiconductor layers on the surface of an n-type InP substrate; an etching step of forming an active layer ridge by etching part of the semiconductor layers; a cleaning step of removing Si having adhered to the surface of the etched semiconductor layers while feeding a source gas for the crystal growth and an etching gas; and a crystal growth step of forming buried layers along both sidewalls of the active layer ridge at a processing temperature higher than that in the cleaning step, and the cleaning step is performed with the ridge being kept in shape.

A semiconductor optical element has a mesa structure in which an active layer is embedded, and comprises a straight propagating section and a spot size converter section being such that a light confinement in the active layer is weaker than that of the straight propagating section, wherein in a same plane parallel to a layer surface of the active layer, an average value of a width of the mesa structure of the straight propagating section is smaller than a value of the width of the mesa structure at the emission facet of the spot size converter section, and at a top part of the mesa structure, an electrode is formed so that an electric current is injected in the active layer across the entire length of the straight propagating section and the spot size converter section.

An optoelectronic device. The optoelectronic device comprising: a plurality of waveguide ridges provided in an array, each waveguide ridge extending away from a semiconductor bed; a plurality of upper contacts, each electrically connected to an upper surface of a respective waveguide ridge, said upper surface being located distal from the semiconductor bed; and a plurality of lower contacts, each located between a respective pair of waveguide ridges and electrically connected to the semiconductor bed.

A germanium waveguide is formed from a P-type silicon substrate that is coated with a heavily-doped N-type germanium layer and a first N-type doped silicon layer. Trenches are etched into the silicon substrate to form a stack of a substrate strip, a germanium strip, and a first silicon strip. This structure is then coated with a silicon nitride layer.

What is provided here are: a step of forming a first semiconductor layer on a base member; a step of forming a mask on the first semiconductor layer; a step of etching the first semiconductor layer by using the mask, to thereby form a semiconductor structure; a step of forming a second semiconductor layer in a region abutting on a side surface of the semiconductor structure, said second semiconductor layer having a convex portion abutting to the mask; a convex-portion removing step of removing the convex portion by supplying an etching gas thereto; and a regrown-layer forming step of supplying a material gas onto the semiconductor structure and the second semiconductor layer, to thereby form a regrown layer; wherein the convex-portion removing step and the regrown-layer forming step are executed in a same manufacturing apparatus.

A vertical-cavity surface-emitting laser (VCSEL) is provided that includes a mesa structure disposed on a substrate. The mesa structure defines an emission axis of the VCSEL. The mesa structure includes a first reflector, a second reflector, and a cascaded active region structure disposed between the first reflector and the second reflector. The cascaded active region structure includes a plurality of cascaded active region layers disposed along the emission axis, where each of the cascade active region layers includes an active region having multi-quantum well and/or dots layers (MQLs), a tunnel junction aligned with the emission axis, and an oxide confinement layer. The oxide confinement layer is disposed between the tunnel junction and MQLs, and has an electrical current aperture defined therein. The mesa structure defines an optical window through which the VCSEL is configured to emit light.

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.