Nec Corporation

Keiro Komatsu

Tatsuya Sasaki

Kiichi Hamamoto

Takeshi Takeuchi

Tomoaki Kato

Yasutaka Sakata

Ikuo Mito

Mitsuhiro Kitamura

Shotaro Kitamura

Kenko Taguchi

Masako Hayashi

Akira Suzuki

Masayuki Yamaguchi

Masahiko Fujiwara

Tomoji Terakado

Kunio Tada

Akira Ajisawa

Masako Yamamoto

Hiroyasu Noguchi

A Mach-Zehnder type optical modulator having a ridge structure including a multiple quantum well wave guide layer expending both in a passive region and in an active phase modulation region on which an electrical field is applied, wherein the wave guide layer is selectively grown by a metal organic vapor phase epitaxy with use of dielectric stripe mask patterns having a large width in the active phase modulation region and a small width in the passive region so that the wave guide layer has a band gap wavelength equal to or near a wavelength of an incidental light in the active phase modulation region and a smaller band gap wavelength smaller than the wavelength of the incidental light in the passive region.

Semiconductor multiple quantum well mach-zehnder optical modulator and method for fabricating the same

A multiple-wavelength light source has a plurality of semiconductor laser devices, a plurality of optical waveguides for leading laser beams from the semiconductor laser devices to respective desired paths, and a plurality of diffraction gratings as external cavities for the semiconductor laser devices. The multiple-wavelength light source can output laser beams of respective wavelengths determined by structural details of the diffraction gratings. The multiple-wavelength light source also has an optical combiner for multiplexing the laser beams from the semiconductor laser devices into a laser beam, an optical wavelength multiplexer/demultiplexer for demultiplexing the laser beam from the optical combiner into a plurality of laser beams of respective desired wavelengths, and outputting the laser beams, a plurality of photodetectors for detecting the laser beams from the optical wavelength multiplexer/demultiplexer and outputting voltages depending on respective detected laser beam power levels, a plurality of heaters disposed near the diffraction gratings for varying temperatures of the diffraction gratings, and a heater current control circuit for supplying currents to the heaters for maximizing the output voltages from the photodetectors.

Multiple-wavelength light source and method of controlling oscillation frequencies thereof

A light wavelength filtering circuit in a wavelength-division multiplexing light communication system minimizes transmission loss in the waveguide after wavelength discrimination by having a linear output waveguide added to an output end of a light wavelength discriminating element, at which a signal having a long wavelength is outputted. A curved output waveguide is added to the rear stage of the output end at which a signal having a relatively short wavelength is outputted. Hence, a radiation loss at the output waveguide at the output end is minimized, while a space between the output light waveguides is being widened. Additionally, a core layer bandgap wavelength at the output waveguide of the long wavelength signal is set to be longer than a core layer band gap wavelength in another region. Hence, a substantial light confinement is formed in a horizontal direction even in the output waveguide at the long wavelength signal side and even if the output waveguide at the long wavelength signal side is curved, and the radiation loss can be reduced.

Light wavelength filtering circuit and manufacturing method thereof

An optical semiconductor device comprises a stripe-mesa structure provided on a semi-insulating substrate. The stripe-mesa structure comprises an undoped light absorption layer sandwiched by cladding layers, and by burying layers on both sides. With this structure, the device capacitance is decreased to provide wide bandwidth and ultra-high speed operation properties. This device can be applied to an optical modulator, an integrated type optical modulator, and an optical detector.

Optical semiconductor device

A semiconductor waveguide layer is provided in an optical semiconductor integrated circuit device comprising a passive region having at least a branch and an active region having at least a laser diode connected to the branch and at least a photo-diode connected to the branch. The active region is in contact with the passive region. The waveguide layer selectively extends over the passive region and the active region. The semiconductor waveguide layer in the active region has a wavelength composition larger than that in the passive region. The waveguide layer has a semiconductor crystal structure which is continuous not only over the active and passive regions but also at a boundary between the active and passive regions.

Optical integrated circuit and method for fabricating the same

A semiconductor optical monolithic integration device has a semiconductor substrate including an active region and a passive region. Epitaxial layers including a multiple quantum well structure have a variation in band gap energy and thickness along a waveguide direction. The epitaxial layers in the active region are selectively grown by a metal organic vapor phase epitaxy on a first selective growth area defined by a first mask pattern provided in the active region except in the passive region. The first mask pattern has a variation in width along the waveguide direction. The epitaxial layers are simultaneously and non-selectively grown on an entire surface of the passive region by the metal organic vapor phase epitaxy and the epitaxial layers have a mesa structure in the active region and a plane structure in the passive region. A cladding layer having a ridged structure is selectively grown by a metal organic vapor phase epitaxy on a second selective growth area defined by a second mask pattern provided in the active and passive regions. The second mask pattern has a constant width. In the active region, the ridged cladding layer completely embeds the mesa structure epitaxial layers and in the passive region the ridged cladding layer are provided on the plane structure epitaxial layers.

Semiconductor optical integrated circuits and method for fabricating the

A semiconductor optical monolithic integration device comprises a semiconductor substrate including an active region and a passive region. Epitaxial layers including a multiple quantum well structure have a variation in band gap energy and thickness along a waveguide direction. The epitaxial layers in the active region are selectively grown by a metal organic vapor phase epitaxy on a first selective growth area defined by a first mask pattern provided in the active region except in the passive region. The first mask pattern has a variation in width along the waveguide direction. The epitaxial layers are simultaneously and non-selectively grown on the entirety of the passive region by metal organic vapor phase epitaxy and epitaxial layers having a mesa structure in the active region and a plane structure in the passive region are formed. A cladding layer having a ridged structure is selectively grown by a metal organic vapor phase epitaxy on a second selective growth area defined by a second mask pattern provided in both the active and passive regions. The second mask pattern has a constant width. In the active region the ridged cladding layer completely embeds the mesa structure epitaxial layers and in the passive region the ridged cladding layer is provided on the plane structure epitaxial layers.

Semiconductor optical integrated circuits

Disclosed herein is a semiconductor optical waveguide-integrated light-receiving device comprising a waveguide-type photodetector and a passive optical waveguide which are selectively formed on the same substrate, wherein the width of mask for a selective growth is varied along the waveguiding direction so as to simultaneously form core layers which differ from each other in absorption edge wavelength. The core layer may be formed with an MQW layer. It is also featured that waveguide width of the photodetector is made larger than the waveguide width of the optical waveguide. The photodetector and the optical waveguide may be buried by an n--InP layer.

Semiconductor optical waveguide-integrated light-receiving device

A semiconductor optical guided-wave device which makes quantization and integration possible and which is fine in structure and low in loss is provided, which comprises a semiconductor substrate, at least one ridge type semiconductor optical waveguide formed thereon and at least one pair of electrodes for applying an electric field to the waveguide. The ridge of the optical waveguide is formed by a selective crystal growth process.. The ridge can be realized preferably in such a method that a mask having an opening at a position where a ridge is formed is patterned to a layer on which the ridge is formed, and the crystal growth of a material for forming the ridge is made by a crystal growth technology such as the MOVPE method. The mask to be used for the crystal growth purpose is preferably a thin dielectric film such as, for example, SiO.sub.2 film. The semiconductor optical waveguide preferably comprises grown layers including a first semiconductor cladding layer, a semiconductor guiding and a second semiconductor cladding layer grown in this order and a ridge having a third semiconductor cladding layer and a semiconductor capping layer laminated in this order on the second semiconductor cladding layer.

Semiconductor optical guided-wave device

In a ridge type or buried hetero type waveguide structure, a semiconductor layer functioning as one selected from a guiding layer, an absorption layer and an active layer includes InGaAsP mixed crystal, and semiconductor cladding layers include InGaAsP mixed crystal having a bandgap energy larger than that of the InGaAsP crystal layer included in the semiconductor layer functioning as one selected therefrom.

Semiconductor device for control of a signal light

There is to provide a method of producing efficiently a custom IC optical integrated circuit with convenient connections between tile optical devices with less loss of the light and with different connection but similar configuration. The optical integrated circuit is comprised of a plurality of ridge-type active optical devices formed of a variable wavelength laser section and a light modulator and a ridge-type passive optical waveguide of a Y-branching optical waveguide for connecting between the ridge-type active optical devices with each other or for connecting the plural ridge-type active optical devices with output waveguides, and ridge sections of the ridge-type active optical device and the ridge-type passive optical waveguide are formed by the selective crystal growth.

Method of producing optical integrated circuit

A semiconductor optical guided-wave device which makes quantization and integration possible and which is fine in structure and low in loss is provided, which comprises a semiconductor substrate, at least one ridge type semiconductor optical waveguide formed thereon and at least one pair of electrodes for applying an electric field to the waveguide. The ridge of the optical waveguide is formed by a selective crystal growth process. The ridge can be realized preferably in such a method that a mask having an opening at a position where a ridge is formed is patterned to a layer on which the ridge is formed, and the crystal growth of a material for forming the ridge is made by a crystal growth technology such as the MOVPE method. The mask to be used for the crystal growth purpose is preferable to be a thin dielectric film such as, for example, SiO.sub.2 film. The semiconductor optical waveguide preferably comprises grown layers including a first semiconductor cladding layer, a semiconductor guiding and a second semiconductor cladding layer grown in this order and a ridge having a third semiconductor cladding layer and a semiconductor capping layer laminated in this order on the second semiconductor cladding layer.

Method of making semiconductor optical guided-wave device

An optical waveguide is fabricated on a substrate of n-type indium phosphide, and comprises a guiding layer of intentionally undoped indium gallium arsenide sandwiched between lower and upper cladding layers of intentionally undoped indium phosphide, wherein the upper cladding layer has a ridge epitaxially grown on a part of an upper surface of the upper cladding layer so that the optical waveguide achieves low propagation losses.

Optical waveguide formed of compound semiconductor materials and process

An optical directional coupler switch is fabricated from a semiconductor substrate having a (111) plane. Thus, refractive indexes are changed for TE and TM modes by electrooptic effect, although the change amount is different between TE and TM modes. Therefore, a switching operation is realized for an incident light having any polarization. A device length L is preferrably set to meet an equation of 'L.sub.TE .ltoreq.L.ltoreq.L.sub.TM ' (L.sub.TE and L.sub.TM are coupling lengths for TE and TM modes) to decrease a cross-talk, even if the coupling lengths are different between TE and TM modes, considering that the difference is small.

Optical directional coupler switch

In a semiconductor layer which has in a semiconductor bistable etalon a refractive index variable, as a result of absorption by excitons, with the intensity of an optical beam incident thereon, an optical guide for the optical beam is surrounded by a cladding portion including atoms which reduce the refractive index in the cladding portion relative to the optical guide and serve as recombination centers for free carries produced by decomposition of the excitons. The semiconductor layer may be either a superlattice layer, such as a GaAs-GaAlAs layer, or a bulk semiconductor layer, such as a GaAs layer. After forming the semiconductor layer on an etch-stop layer which is formed on a semiconductor substrate for chemical etch of the substrate for a window, the atoms are injected into the surrounding portion as by bombarding an exposed surface of the semiconductor layer by hydrogen ions with a mask selectively formed on the exposed area to cover an area contiguous on the exposed surface to a columnar portion which becomes the optical guide. The hydrogen ions automatically become the atoms of the above-described type in the surrounding portion.

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Tokyo, Japan

Keiro Komatsu