Abstract: An active layer having a p-type quantum dot structure is disposed over a lower cladding layer made of semiconductor material of a first conductivity type. An upper cladding layer is disposed over the active layer. The upper cladding layer is made of semiconductor material, and includes a ridge portion and a cover portion. The ridge portion extends in one direction, and the cover portion covers the surface on both sides of the ridge portion. A capacitance reducing region is disposed on both sides of the ridge portion and reaching at least the lower surface of the cover portion. The capacitance reducing region has the first conductivity type or a higher resistivity than that of the ridge portion, and the ridge portion has a second conductivity type. If the lower cladding layer is an n-type, the capacitance reducing region reaches at least the upper surface of the lower cladding layer.

Abstract: An active layer having a p-type quantum dot structure is disposed over a lower cladding layer made of semiconductor material of a first conductivity type. An upper cladding layer is disposed over the active layer. The upper cladding layer is made of semiconductor material, and includes a ridge portion and a cover portion. The ridge portion extends in one direction, and the cover portion covers the surface on both sides of the ridge portion. A capacitance reducing region is disposed on both sides of the ridge portion and reaching at least the lower surface of the cover portion. The capacitance reducing region has the first conductivity type or a higher resistivity than that of the ridge portion, and the ridge portion has a second conductivity type. If the lower cladding layer is an n-type, the capacitance reducing region reaches at least the upper surface of the lower cladding layer.

Abstract: An intrinsic GaAs waveguide layer is formed on a p-type AlGaAs cladding layer, a quantum dot active layer is formed further thereon. An n-type AlGaAs cladding layer is formed on the center portion of the quantum dot active layer. Thus-configured semiconductor laser is allowed to successfully suppress the area of the p-n junction plane to a small level, and to obtain a high level of reliability, because there is no need of processing the center portion of the quantum dot active layer, contributive to laser oscillation.

Abstract: A semiconductor light emitting device is provided with a GaAs substrate, a quantum dot active layer formed over the GaAs substrate, a GaAs layer formed above or below the quantum dot active layer, and a diffraction grating formed from InGaP or InGaAsP and periodically provided along an propagating direction of light in the GaAs layer.

Abstract: A quantum dot semiconductor device includes an active layer having a plurality of quantum dot layers each including a composite quantum dot formed by stacking a plurality of quantum dots and a side barrier layer formed in contact with a side face of the composite quantum dot. The stack number of the quantum dots and the magnitude of strain of the side barrier layer from which each of the quantum dot layers is formed are set so that a gain spectrum of the active layer has a flat gain bandwidth corresponding to a shift amount of the gain spectrum within a desired operation temperature range.

Abstract: The present invention provides an ultra-mini and low cost refractive index measuring device applicable to biochemical measurements of an extremely minute amount of a sample. The refractive index measuring device uses a photonic crystal without any requirement of an external spectrograph or the like. The micro sensor device according to the present invention includes a light source emitting light with a single wavelength, a microcavity in which a resonant wavelength varies depending on a position thereof. A refractive index of a material to be measured is measured based on positional information by detecting a transmitting position of light changing in response to a change of a refractive index of the measured material. The micro sensor device according to the present invention enables measurement of a refractive index of a material to be measured without using a large-scale spectrograph.

Abstract: A semiconductor light emitting device includes a lower cladding layer, an active layer, and an AlGaAs upper cladding layer mounted on a GaAs substrate. The semiconductor light emitting device has a ridge structure including the AlGaAs upper cladding layer. The semiconductor light emitting device further includes an InGaAs etching stop layer provided in contact with the lower side of the AlGaAs upper cladding layer. The InGaAs etching stop layer has a band gap greater than that of the active layer.

Abstract: An active layer having a p-type quantum dot structure is disposed over a lower cladding layer made of semiconductor material of a first conductivity type. An upper cladding layer is disposed over the active layer. The upper cladding layer is made of semiconductor material, and includes a ridge portion and a cover portion. The ridge portion extends in one direction, and the cover portion covers the surface on both sides of the ridge portion. A capacitance reducing region is disposed on both sides of the ridge portion and reaching at least the lower surface of the cover portion. The capacitance reducing region has the first conductivity type or a higher resistivity than that of the ridge portion, and the ridge portion has a second conductivity type. If the lower cladding layer is an n-type, the capacitance reducing region reaches at least the upper surface of the lower cladding layer.

Abstract: An active layer (18) is formed over a semiconductor substrate having a pair of facets (15A, 15B) mutually facing opposite directions. An upper cladding layer (19) is formed on the active layer, having a refractive index lower than that of the active layer. A diffraction grating (25) is disposed in the upper cladding layer on both sides of a distributed feedback region in a waveguide region (22), the waveguide region extending from one facet to the other of the semiconductor substrate. End regions (22B) are defined at both ends of the waveguide region and the distributed feedback region (22A) is disposed between the end regions. Low refractive index regions (26) are disposed in the upper cladding layer on both sides of each of the end regions of the waveguide region, the low refractive index regions having a refractive index lower than that of the upper cladding layer.

Abstract: The method of manufacturing the semiconductor device comprises the step of forming quantum dots 16 on a base layer 10 by self-assembled growth; the step of irradiating Sb or GaSb to the surface of the base layer 10 before or in the step of forming quantum dots 16; the step of etching the surfaces of the quantum dots 16 with an As raw material gas to thereby remove an InSb layer 18 containing Sb deposited on the surfaces of the quantum dots 16; and growing a capping layer 22 on the quantum dots 16 with the InSb layer 18 removed.

Abstract: A semiconductor light emitting element improving luminous efficiency has: a semiconductor substrate, an N-type cladding layer formed over the substrate; a barrier layer formed over the cladding layer; a quantum dot layer formed over the barrier layer, the quantum dot layer including quantum dots having a band gap smaller than that of the barrier layer and a buried layer having a band gap larger than that of the quantum dots, the buried layer covering a sidewall of the quantum dots; a P-type semiconductor layer formed over the quantum dot layer, the semiconductor layer having a band gap smaller than that of the barrier layer; a barrier layer formed over the P-type semiconductor layer, the barrier layer having a band gap larger than those of the quantum dots and of the semiconductor layer; and a p-type cladding layer formed over the barrier layer. Therefore, holes generated in the P-type semiconductor layer are prevented from flowing into the barrier layer and the buried layer.

Abstract: An optical semiconductor device includes: a waveguide structure including layers grown over a semiconductor substrate, having a width defined by sidewalls formed by etching the layers, and including a wide, a narrow, and an intermediate width portion, formed along a propagation direction; and a diffraction grating formed on the sidewalls of at least one of the wide and narrow width portions of the waveguide structure, the diffraction grating having vertical grooves periodically disposed along the propagation direction and defining a wavelength of propagation light, wherein the narrow width portion is formed in such a manner that a loss of 50% or more is given to a higher order transverse mode. An optical semiconductor device having a vertical diffraction grating is provided which can suppress generation of a higher order transverse mode and an increase in a device resistance.

Abstract: A single-photon generator includes a single-photon generating device generating a single-photon pulse having a wavelength on the shorter wavelength side than a communication wavelength band, and a single-photon wavelength conversion device performing wavelength conversion of the single-photon pulse into a single-photon pulse of the communication wavelength band, using pump pulse light for single-photon wavelength conversion.

Abstract: A single-photon generating device is configured to have a solid substrate including abase portion, and a pillar portion which is formed on the surface side of the base portion with a localized level existent in the vicinity of the tip of the base portion. The above pillar portion is formed to have a larger cross section on the base portion side than the cross section on the tip side, so that the light generated from the localized level is reflected on the surface, propagated inside the pillar portion, and output from the back face side of the base portion.

Abstract: The present invention provides an ultra-mini and low cost refractive index measuring device applicable to biochemical measurements of an extremely minute amount of a sample. The refractive index measuring device uses a photonic crystal without any requirement of an external spectrograph or the like. The micro sensor device according to the present invention includes a light source emitting light with a single wavelength, a microcavity in which a resonant wavelength varies depending on a position thereof. A refractive index of a material to be measured is measured based on positional information by detecting a transmitting position of light changing in response to a change of a refractive index of the measured material. The micro sensor device according to the present invention enables measurement of a refractive index of a material to be measured without using a large-scale spectrograph.

Abstract: An intrinsic GaAs waveguide layer is formed on a p-type AlGaAs cladding layer, a quantum dot active layer is formed further thereon. An n-type AlGaAs cladding layer is formed on the center portion of the quantum dot active layer. Thus-configured semiconductor laser is allowed to successfully suppress the area of the p-n junction plane to a small level, and to obtain a high level of reliability, because there is no need of processing the center portion of the quantum dot active layer, contributive to laser oscillation.

Abstract: The light emitting device comprises a substrate 10 of a p-type semiconductor; an active layer 20 formed of a plurality of quantum dot layers 18 stacked, the quantum dot layers 18 having three-dimensional grown islands self-formed by S-K mode, respectively; and an n-type semiconductor layer 22 formed over the active layer. Because of the p-type semiconductor, over which the active layer 20 is formed on, and the n-type semiconductor, which is formed over the active layer 20, lower layer regions of the active layer 20, where good quantum dots 19 are formed are nearer to regions of the active layer 20, which are nearer to the p-type semiconductor. Accordingly, the radiation recombination between the holes and electrons takes place mainly in the regions where those of the quantum dots, which are of good quality. Thus, even when a number of the quantum dot layers 18 are stacked, good device characteristics can be obtained.

Abstract: A quantum semiconductor device including quantum dots formed by S-K growth process taking place in a heteroepitaxial system wherein the relationship between the energy level of light holes and the energy level of heavy holes in the valence band is changed by optimizing the in-plane strain and the vertical strain accumulated in a quantum dot.

Abstract: A quantum semiconductor device includes quantum dots formed by S-K growth process taking place in a heteroepitaxial system wherein the relationship between the energy level of light holes and the energy level of heavy holes in the valence band is changed by optimizing the in-plane strain and the vertical strain accumulated in a quantum dot.