Mitsubishi Denki Kabushiki Kaisha

Katsuhiko Goto

Tohru Takiguchi

Etsuji Omura

Shogo Takahashi

Yutaka Mihashi

Hirotaka Kizuki

Akira Takemoto

Harumi Namba

Toshitaka Aoyagi

Go Sakaino

Hirofumi Namizaki

Shigeki Kageyama

Kouji Yamashita

Yoshihiro Kokubo

Seiji Minamihara

Toru Takiguchi

A method of fabricating an integrated waveguide device includes forming a ridge having a width that varies in a tapered shape along the [011] direction on a semiconductor substrate and growing a laminated layer structure including a light waveguide layer where the width varies in a tapered shape of the ridge so that a waveguide has a tapered shape in the laminated layer structure, thereby producing an integrated waveguide device having a tapered light waveguide. The thickness of the semiconductor layer and the wavelength guided by the waveguide are controlled with high precision and the reliability of the device is enhanced.

Integrated waveguide device and method of fabricating the integrated

A semiconductor optical device includes a first semiconductor layer, and a diffraction grating disposed on the first semiconductor layer. The diffraction grating includes portions of a superlattice layer grown on the first semiconductor layer and including alternatingly arranged second semiconductor layers of a semiconductor material in which mass transport hardly occurs during growth of other semiconductor layers and third semiconductor layers of a semiconductor material different from the material of the second semiconductor layers. The device includes a fourth semiconductor layer burying the diffraction grating. In this structure, since the second semiconductor layers are included in the diffraction grating, the shape of the diffraction grating is maintained during the vapor phase deposition of the fourth semiconductor layer. Therefore, the thickness, amplitude, and pitch of the diffraction grating that determine the optical coupling constant are controlled with high precision.

Semiconductor optical device

An optical module includes a substrate having an upper surface and a groove on the upper surface; an optical fiber having a core and an end facet, disposed in the groove of the substrate; an optical semiconductor device having an upper surface and a light interactive area on the upper surface optically coupled to the optical fiber; and a block having a side surface on which the optical semiconductor device is fixed and a lower surface perpendicular to the side surface. The optical semiconductor device is fixed onto the side surface of the block so that the distance from the light interactive area to the lower surface of the block is equal to the distance from the core of the optical fiber to the upper surface of the substrate; and the block is disposed on the substrate, with the lower surface contacting the upper surface of the substrate, so that the light interactive area is opposed to the end facet of the optical fiber. The core of the optical fiber and the light interactive area are accurately aligned with the surface of the substrate as a reference regardless of the thickness of the substrate, resulting in a high coupling efficiency between the optical fiber and the optical semiconductor device.

Optical module and method of fabricating optical module

A quantum wire structure includes a substrate of a first semiconductor having a surface and a first band gap energy; a layer of a second semiconductor having a second band gap energy and including second semiconductor elements disposed on the surface of the substrate spaced apart in a pattern at an interval of no more than 100 nm, each second semiconductor element having a trapezoidal cross-section transverse to the surface of the substrate and including an upper surface generally parallel to the surface of the semiconductor substrate and sloped surfaces oriented so that a third semiconductor does not grow on the sloped surfaces; a layer of a third semiconductor having a third band gap energy smaller than the first and second band gap energies disposed on the upper surfaces of the second semiconductor elements and on the surface of the substrate between adjacent second semiconductor elements but not on the sloped surfaces; and a layer of a fourth semiconductor having a fourth band gap energy larger than the third band gap energy disposed on and burying the layers of the second and third semiconductors.

Method of fabricating a diffraction grating and a distributed feedback

A semiconductor device includes a substrate having a lattice constant and a stress compensation strained quantum well layer including compressively strained layers having a lattice constant larger than the lattice constant of the substrate and tensively strained layers having a lattice constant smaller than the lattice constant of the substrate which are alternatingly laminated on the substrate, wherein the average strain of the stress compensation strained quantum well layer is a positive quantity. Therefore, the critical thickness of the strained quantum well layer is increased so that the degree of freedom in designing the strained quantum well layer is increased, resulting in a semiconductor device with improved characteristics.

Strained quantum well structure

A semiconductor optical modulator includes an active region including a multi quantum well structure. Thereby, it is possible to absorb laser light having two polarization wave modes to a high degree as well as increase the number of quantum wells without fracturing the crystal, thereby providing a modulator having no polarization plane dependency and an increased extinction ratio. Further, a plurality of electrodes, each having an aperture, are provided at an upper surface and an electrode having the same number of apertures as on the upper surface is provided at a lower surface opposite the other electrodes. Multiple laser light beams incident from the apertures at the upper surface are respectively modulated and output from the apertures at the opposing lower surface. Therefore, in the active region, laser light beams including both TE and TM modes are absorbed or transmitted by the modulator without dependency on their respective polarization planes.

Semiconductor optical modulator

A semiconductor laser device includes an active layer having a multiquantum well (MQW) structure including well layers and barrier layers, each well layer being disposed between a pair of barrier layers. In this structure, the barrier layers have respective band gap energies that gradually decrease from a largest value in a central part of the MQW structure toward interfaces of the MQW structure with other layers of the laser and the well layers have respective band gap energies that gradually increase from a smallest value in the central part of the MQW structure toward the interfaces. A semiconductor laser device that produces uniform charge carrier injection, has a high thermal electron emission efficiency, and a broad modulation bandwidth is realized.

Semiconductor laser device having a high emission efficiency and a large

A method of fabricating a quantum wire structure includes forming a first insulating film on a surface of a substrate of a first semiconductor, the insulating film including a pattern of spaced apart mask elements having a width not exceeding 100 nm; selectively growing a layer of a second semiconductor on the surface of the substrate employing the insulating film as a growth mask, the layer including spaced apart second semiconductor elements, each second semiconductor element having a trapezoidal cross-section transverse to the surface of the substrate and including an upper surface generally parallel to the surface of the substrate and sloped surfaces oriented so that a third semiconductor does not grow on the sloped surfaces; growing a layer of a third semiconductor having a smaller band gap energy than the band gap energies of the first and second semiconductors on the upper surfaces of the second semiconductor elements and on the surface of the substrate between adjacent second semiconductor elements but not on the sloped surfaces of the second semiconductor elements, the third semiconductor forming quantum wires; and growing a layer of a fourth semiconductor having a band gap energy larger than the band gap energy of the third semiconductor on and burying the layers of the second and third semiconductors.

Method of fabricating quantum wire

A semiconductor optical device includes a first semiconductor layer, and a diffraction grating disposed on the first semiconductor layer. The diffraction grating includes portions of a superlattice layer grown on the first semiconductor layer and including alternatingly arranged second semiconductor layers of a semiconductor material in which mass transport hardly occurs, during growth of other semiconductor layers and third semiconductor layers of a semiconductor material different from the material of the second semiconductor layers. The device includes a fourth semiconductor layer burying the diffraction grating. In this structure, since the second semiconductor layers are included in the diffraction grating, the shape of the diffraction grating is maintained during the vapor phase deposition of the fourth semiconductor layer. Therefore, the thickness, amplitude, and pitch of the diffraction grating that determine the optical coupling constant are controlled with high precision.

Semiconductor optical devices

A semiconductor laser includes a semiconductor substrate of a first conductivity type, a gain guiding structure comprising of a first conductivity type, a lower cladding layer disposed on the substrate, an active layer disposed on the lower cladding layer and having a light emitting region, and an upper cladding layer of a second conductivity type, opposite the first conductivity type, disposed on the active layer, and a multiquantum barrier layer interposed between the upper cladding layer and the active layer excluding the light emitting region. In this structure, the multiquantum barrier layer reduces leakage current flowing outside of the light emitting region of the active layer and increases effective current flowing into the light emitting region, whereby the light output of the laser is significantly increased.

Semiconductor laser device

An integrated semiconductor laser including at least two active regions, each active region oscillating at a respective, different wavelength, the integrated semiconductor laser including a common semiconductor substrate of a first conductivity type; a semiconductor first cladding layer of the first conductivity type disposed on the substrate; at least two spaced apart active regions disposed on the first cladding layer within a common active layer, the active layer including at least one compound semiconductor quantum well layer sandwiched between compound semiconductor quantum barrier layers, the quantum barrier layers having a larger energy band gap than and including at least one more element than the quantum well layer, the at least one more element of the quantum barrier layers penetrating farther into the quantum well layer at the first active region than into the quantum well layer at the second active region; a second cladding layer disposed on each of the first and second active regions; and respective electrical contacts to the first and second active regions through the first and second cladding layers disposed on opposite sides of each of the first and second active regions.

Integrated semiconductor laser

A method of making an integrated semiconductor laser on a common substrate including at least two active regions, each active region oscillating at a respective, different wavelength, including producing a precursor laser structure by successively growing on a semiconductor substrate a first conductivity type semiconductor first cladding layer, an active layer including at least one compound semiconductor quantum well layer sandwiched between compound semiconductor quantum barrier layers, and a second conductivity type semiconductor second cladding layer, the quantum barrier layers having a larger energy band gap than and including at least one more element than the quantum well layer, annealing the precursor structure including controlling at first and second spaced apart regions the diffusion of the at least one more element from the quantum barrier layers into the quantum well layer to produce first and second spaced apart active regions in the active layer having different effective lasing energy band gaps, and forming respective electrical contacts to the first and second cladding layers on opposite sides of each of the first and second active regions.

Integrated semiconductor laser producing light of different wavelengths

A semiconductor optical element includes a quantum well structure having a crystalline well layer of (Al.sub.x Ga.sub.1-x).sub.1-z In.sub.z P.sub.y As.sub.1-y (O.ltoreq.x&lt;1, O.ltoreq.y&lt;1, O&lt;z&lt;1) having a lattice constant that matches crystalline InP and two barrier layers of crystalline (Al.sub.x' Ga.sub.1-x').sub.1-z In.sub.z P.sub.y As.sub.1-y (x&lt;x'.ltoreq.1) having lattice constant that matches crystalline wherein and at least a portion of the quantum well structure is disordered.

Semiconductor optical element

A buried heterojunction semiconductor laser appropriate for integration with other electronic circuitry and method of producing same, in which the width of a central stripe of the active region can be reduced beyond the physical size limitations of the connecting electrode so as to allow the semiconductor laser to oscillate in a stable manner and with low threshold current. The semiconductor laser is provided with a portion of the surface of the upper cladding layer located above the disordered active layer regions electrically connected with the upper cladding layer located above the nondisordered central stripe. As a result, the central stripe electrode can be of a width larger than that of the central stripe itself.

Growing community of inventors

Itami, Japan

Katsuhiko Goto