Abstract: A semiconductor light-receiving element, includes: a semiconductor substrate; a high-concentration layer of a first conductivity type formed on the semiconductor substrate; a low-concentration layer of the first conductivity type formed on the high-concentration layer of the first conductivity type and in contact with the high-concentration layer of the first conductivity type; a low-concentration layer of a second conductivity type configured to form a PN junction interface together with the low-concentration layer of the first conductivity type; and a high-concentration layer of the second conductivity type formed on the low-concentration layer of the second conductivity type and in contact with the low-concentration layer of the second conductivity type. The low-concentration layers have a carrier concentration of less than 1×1016/cm3. The high-concentration layers have a carrier concentration of 1×1017/cm3 or more.

Abstract: A semiconductor light emitting device includes a microstrip substrate with a single-ended transmission line on a top surface, wherein the single-ended transmission line extends from a first end portion to a second end portion, the microstrip substrate has a ground plane on a bottom surface, and the ground plane is opposed and bonded to the conductive pattern. The single-ended transmission line includes a first section and a second section, wherein the second section extends from the first section and includes the second end portion. The second section is lower in characteristic impedance than the first section. A load circuit that includes the wire, the optical modulator, and the termination resistor is electrically connected between the second end portion and the conductive pattern. The load circuit is equal to or lower in the characteristic impedance than the second section.

Abstract: A semiconductor optical device includes: a buried layer having a side surface, an upper surface, and an intermediate region; an insulating film on the upper surface of the buried layer; and an electrode including a mesa electrode, a pad electrode, and a lead-out electrode. The upper surface of the buried layer has an outer edge including a first edge extending along the first direction and a second edge extending along a second direction. The intermediate region includes an upright surface that stands straight between the side surface and the first edge, and a slope surface that slopes more gently than the upright surface and extends downward from the second edge. The lead-out electrode includes a portion on the insulating film and connected to the pad electrode, another portion on the intermediate region and through the slope surface, and another portion connected to the mesa electrode.

Abstract: A semiconductor optical device may include a semiconductor substrate; a compound semiconductor layer on the semiconductor substrate; an additional insulating film on the pedestal portion of the compound semiconductor layer, the additional insulating film having an upper surface and a side surface at an inner obtuse angle between them; a passivation film covering the compound semiconductor layer and the additional insulating film except at least part of the mesa portion, the passivation film having a protrusion raised by overlapping with the additional insulating film; a mesa electrode on the at least part of the mesa portion; a pad electrode on the passivation film within the protrusion; and an extraction electrode on the passivation film, the extraction electrode being continuous within and outside the protrusion, the extraction electrode connecting the pad electrode and the mesa electrode, the extraction electrode being narrower in width than the pad electrode.

Abstract: 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.

Abstract: A semiconductor light-receiving element includes a substrate; a light-receiving mesa portion, formed on top of the substrate, including a first semiconductor layer of a first conductivity type, an absorption layer, and a second semiconductor layer of a second conductivity type; a light-receiving portion electrode, formed above the light-receiving mesa portion, connected to the first semiconductor layer; a pad electrode formed on top of the substrate; and a bridge electrode, placed so that an insulating gap is interposed between the bridge electrode and the second semiconductor layer, configured to connect the light-receiving portion electrode and the pad electrode on top of the substrate, the bridge electrode being formed in a layer separate from layers of the light-receiving portion electrode and the pad electrode.

Abstract: A printed circuit board includes a first transmission line provided on an insulating base, a first ground conductor, a notch portion that exposes a part of the first ground conductor, a conductor provided in the notch portion and electrically connected to the first ground conductor, and a first electrode exposed on a main surface of the insulating base facing a flexible board and electrically connected to the first transmission line. The flexible board includes a second transmission line provided on an insulating sheet, a second ground conductor, a second electrode exposed on a main surface of the insulating sheet facing the printed circuit board and connected to the second transmission line, and a third electrode exposed on the main surface of the insulating sheet and connected to the second ground conductor. The conductor and the third electrode are connected by solder.

Abstract: A ridge type semiconductor optical device includes a first conductivity type semiconductor layer including at least a first stripe section; an active layer including at least an active stripe section on the first stripe section; a second conductivity type semiconductor layer including at least a second stripe section on the active stripe section; a ridge electrode on the second stripe section; an insulation film on an end face of each of the first stripe section, the active stripe section, and the second stripe section; and a film heater on the insulation film, the film heater overlapping with the end face of at least the first stripe section.

Abstract: A semiconductor optical amplifier integrated laser includes a semiconductor laser oscillator portion that oscillates laser light having a wavelength included in a gain band and a semiconductor optical amplifier portion that amplifies laser light output from the semiconductor laser oscillator portion. The semiconductor laser oscillator portion and the semiconductor optical amplifier portion have one common p-i-n structure, the common p-i-n structure includes an active layer, a cladding layer provided apart from the active layer, and a common functional layer formed in the cladding layer, and the common functional layer includes a first portion that reflects light having a wavelength within the gain band in the semiconductor laser oscillator portion and a second portion that transmits light having a wavelength within the gain band in the semiconductor optical amplifier portion.

Abstract: A semiconductor light-receiving element, includes: a semiconductor substrate; a high-concentration layer of a first conductivity type formed on the semiconductor substrate; a low-concentration layer of the first conductivity type formed on the high-concentration layer of the first conductivity type and in contact with the high-concentration layer of the first conductivity type; a low-concentration layer of a second conductivity type configured to form a PN junction interface together with the low-concentration layer of the first conductivity type; and a high-concentration layer of the second conductivity type formed on the low-concentration layer of the second conductivity type and in contact with the low-concentration layer of the second conductivity type. The low-concentration layers have a carrier concentration of less than 1×1016/cm3. The high-concentration layers have a carrier concentration of 1×1017/cm3 or more.

Abstract: 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, a first, second, and third sublayer, the first and 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, and the second sublayer consisting of one or more layers selected from InGaAs, InAlAs, InGaAlAs, InGaAsP, and InAlAsP.

Abstract: A transmitter optical subassembly may include an optical modulator for modulating output light from the light source. The optical modulator has a characteristic that a current depending on amount of optical absorption has a positive correlation with an applied voltage thereto. The transistor at the second terminal is connected in series to the optical modulator. A drive voltage applied to the optical modulator and the transistor is divided into a first voltage applied to the optical modulator and a second voltage applied to the transistor. A drive current flowing through the optical modulator and the transistor depends on the control signal input to the first terminal. The first voltage is based on the drive current and is subject to the characteristic of the optical modulator. The second voltage fluctuates in response to the first voltage.

Abstract: An optical subassembly includes an eyelet including a first through-hole penetrating from a first surface through a second surface; a first lead terminal, which is to be inserted into the first through-hole, and is configured to transmit an electric signal; a dielectric material, which is filled in a space between the first through-hole and the first lead terminal; a device mounting substrate, on which an optical device is to be mounted, and which includes a first conductor pattern configured to transmit the electric signal to the optical device; a metal block having mounted thereon the device mounting substrate; a temperature regulator placed between the metal block and the eyelet; a relay substrate including a second conductor pattern, which is configured to transmit the electric signal to the optical device; a seat, which protrudes from the first surface in a direction extended from the first through-hole, and has a third surface mounting the relay substrate; and a spacer interposed between the third surfa

Abstract: A semiconductor optical device includes: a laser for emitting light; a modulator for modulating the light using an electroabsorption effect; a chip capacitor that is electrically connected in parallel to the laser; a chip inductor that is electrically connected in series to the chip capacitor, is electrically connected in series to the laser and the chip capacitor as a whole, and includes a first terminal and a second terminal; a solder or a conductive adhesive that directly bonds the first terminal of the chip inductor and the chip capacitor to each other; an electrical wiring group in which the laser, the modulator, the chip capacitor, and the chip inductor are electrically connected to each other; and a substrate on which the laser, the modulator, the chip capacitor, and the chip inductor are mounted.

Abstract: A electro-absorption optical modulator includes a multiple quantum well composed of a plurality of layers including a plurality of quantum well layers and a plurality of barrier layers that are alternately stacked, the plurality of quantum well layers and the plurality of barrier layers including an acceptor and a donor; a p-type semiconductor layer in contact with an uppermost layer of the plurality of layers; and an n-type semiconductor layer in contact with a lowermost layer of the plurality of layers, the multiple quantum well being 10% or more and 150% or less of the p-type semiconductor layer in a p-type carrier concentration, and in the multiple quantum well, an effective carrier concentration which corresponds to a difference between the p-type carrier concentration and an n-type carrier concentration is ±10% or less of the p-type carrier concentration of the multiple quantum well.

Abstract: An optical module includes a photoelectric converter configured to receive an optical signal having an intensity that changes at one of a first frequency or a second frequency that is higher than the first frequency, and convert the optical signal into a current signal corresponding to the intensity of the optical signal; a signal processor configured to acquire, when the optical signal has the intensity that changes at the first frequency, wavelength information set on a transmitting side based on a ratio between a plurality of signal intensities included in the current signal relating to the optical signal having the intensity that changes at the first frequency; and a decoder configured to generate, when the optical signal has the intensity that changes at the second frequency, communication data from the current signal relating to the optical signal having the intensity that changes at the second frequency.

Abstract: 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.

Abstract: An optical communication module includes a first power-supplied terminal to be brought into contact with a first power supply terminal to have a first power supply voltage applied thereto; a second power-supplied terminal to be brought into contact with the second power supply terminal to have a second power supply voltage applied thereto; a signal processing circuit, which is connected to the first power-supplied terminal and the second power-supplied terminal, configured to perform processing on a signal; and a power control circuit, which is provided between the first power-supplied terminal and the signal processing circuit, configured to control connection between the first power-supplied terminal and the signal processing circuit based on a voltage applied to the second power-supplied terminal.

Abstract: A buried typed semiconductor optical device includes a semiconductor substrate having a pair of grooves extending in a first direction. An upper surface of a buried layer has a first region that is adjacent to a mesa stripe structure, overlaps with a corresponding one of the pair of grooves, is inclined so as to be higher in a second direction from the mesa stripe structure, and on which a passivation film is not formed. The upper surface of the buried layer has a second region that does not overlap with any of the pair of grooves, is flat, and is higher than a lower end of the first region, and on which the passivation film is formed. The upper surface of the buried layer has a connection region between the first region and the second region at a same height as the second region.

Abstract: A semiconductor optical device includes an element structure layer that includes a mesa stripe extending in a first direction; an electrode film that covers at least an upper surface of the mesa stripe; an electrode pad portion that covers a part of a first region positioned in a second direction, intersecting the first direction, relative to the mesa stripe on an upper surface of the element structure layer and is electrically connected to the electrode film; a first dummy electrode that covers another part of the first region and is electrically insulated from the electrode film; and a second dummy electrode that covers at least a part of a second region positioned in a third direction, opposite to the second direction, relative to the mesa stripe on the upper surface of the element structure layer and is electrically insulated from the electrode film, wherein the first dummy electrode includes a first portion disposed in the first direction relative to the electrode pad portion and a second portion dispose