Patents by Inventor Shotaro Kitamura
Shotaro Kitamura has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 8477819Abstract: Disclosed is a distributed feedback semiconductor laser diode device capable of operating at a high output ratio of forward/backward optical power while ensuring satisfactory stability of single-mode oscillation. The distributed feedback semiconductor laser diode device is configured to include a diffraction grating formed in an optical waveguide thereof. In a partial region of the optical waveguide, there is formed an alternately repetitive pattern of a grating part possessing a distributive refractivity characteristic and a no-grating space part possessing a uniform refractivity characteristic. The no-grating space part possessing a uniform refractivity characteristic has an optical path length that is half an integral multiple of a wavelength of laser oscillation, and the grating part possessing a distributive refractivity characteristic includes at least five grating periods.Type: GrantFiled: November 22, 2010Date of Patent: July 2, 2013Assignee: Renesas Electronics CorporationInventor: Shotaro Kitamura
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Publication number: 20110134955Abstract: Disclosed is a distributed feedback semiconductor laser diode device capable of operating at a high output ratio of forward/backward optical power while ensuring satisfactory stability of single-mode oscillation. The distributed feedback semiconductor laser diode device is configured to include a diffraction grating formed in an optical waveguide thereof. In a partial region of the optical waveguide, there is formed an alternately repetitive pattern of a grating part possessing a distributive refractivity characteristic and a no-grating space part possessing a uniform refractivity characteristic. The no-grating space part possessing a uniform refractivity characteristic has an optical path length that is half an integral multiple of a wavelength of laser oscillation, and the grating part possessing a distributive refractivity characteristic includes at least five grating periods.Type: ApplicationFiled: November 22, 2010Publication date: June 9, 2011Inventor: Shotaro KITAMURA
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Patent number: 7666694Abstract: An improved throughput can be presented, since an influence of the deterioration in crystallinity created in the epitaxial layer can be eliminated by a simple and easy method, and a semiconductor laser device having stabilized properties such as threshold current, slope efficiency, device life time and the like can be presented. A method for manufacturing a semiconductor laser device according to the present invention comprises: forming partially a diffraction grating on a surface of a semiconductor substrate or on a film on the surface of the semiconductor substrate; and forming a multiple-layered film by forming an epitaxial layer on a surface of the diffraction grating. The operation of forming the diffraction grating includes an operation of forming the diffraction grating so that a width of the diffraction grating in a direction that is orthogonal to a cavity direction of the semiconductor laser device is presented as a width equal to or longer than a sum of a mesa width and 30 ?m.Type: GrantFiled: September 18, 2006Date of Patent: February 23, 2010Assignee: NEC Electronics CorporationInventors: Masahide Kobayashi, Shotaro Kitamura
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Patent number: 7633986Abstract: A distributed feedback laser diode comprises a phase-shifting portion in diffraction gratings. The magnitude of a phase shift in the phase-shifting portion is 8?/40 to 9?/40, ? representing twice the distance between the diffraction gratings. A main mode stands on a lower wavelength side than the center of a stop band when an injected current is of a level of a threshold current, whereas the main mode is shifted to the center of the stop band and a sub mode is suppressed from growing when the injected current is of a level of an operating current.Type: GrantFiled: May 29, 2007Date of Patent: December 15, 2009Assignee: NEC Electronics CorporationInventors: Shotaro Kitamura, Yasutaka Sakata
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Publication number: 20070280321Abstract: A distributed feedback laser diode comprises a phase-shifting portion in diffraction gratings. The magnitude of a phase shift in the phase-shifting portion is 8 ?/40 to 9 ?/40, ? representing twice the distance between the diffraction gratings. A main mode stands on a lower wavelength side than the center of a stop band when an injected current is of a level of a threshold current, whereas the main mode is shifted to the center of the stop band and a sub mode is suppressed from growing when the injected current is of a level of an operating current.Type: ApplicationFiled: May 29, 2007Publication date: December 6, 2007Applicant: NEC ELECTRONICS CORPORATIONInventors: Shotaro Kitamura, Yasutaka Sakata
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Publication number: 20070064759Abstract: An improved throughput can be presented, since an influence of the deterioration in crystallinity created in the epitaxial layer can be eliminated by a simple and easy method, and a semiconductor laser device having stabilized properties such as threshold current, slope efficiency, device life time and the like can be presented. A method for manufacturing a semiconductor laser device according to the present invention comprises: forming partially a diffraction grating on a surface of a semiconductor substrate or on a film on the surface of the semiconductor substrate; and forming a multiple-layered film by forming an epitaxial layer on a surface of the diffraction grating. The operation of forming the diffraction grating includes an operation of forming the diffraction grating so that a width of the diffraction grating in a direction that is orthogonal to a cavity direction of the semiconductor laser device is presented as a width equal to or longer than a sum of a mesa width and 30 ?m.Type: ApplicationFiled: September 18, 2006Publication date: March 22, 2007Inventors: Masahide Kobayashi, Shotaro Kitamura
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Patent number: 6141477Abstract: The invention provides a semiconductor optical amplification element which reduces noise light emission and increases saturation output power. The semiconductor optical amplification element has an optical waveguide which includes a core layer formed from an active layer acting as an optical amplification medium and amplifies and outputs an optical signal without electrically converting. The light reflection factor on an inputting side end of the element for the optical signal is lower than the light reflection factor on another outputting side end of the element.Type: GrantFiled: January 6, 1998Date of Patent: October 31, 2000Assignee: NEC CorporationInventor: Shotaro Kitamura
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Patent number: 6052222Abstract: A semiconductor optical amplifier which has a good extinction ratio and a simple structure includes an optical waveguide having at least a curved portion. The optical waveguide has light input and output ends offset from each other to keep optical fibers out of alignment with each other at respective opposite ends of the optical waveguide.Type: GrantFiled: December 19, 1997Date of Patent: April 18, 2000Assignee: NEC CorporationInventor: Shotaro Kitamura
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Patent number: 5770466Abstract: 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.Type: GrantFiled: March 8, 1995Date of Patent: June 23, 1998Assignee: NEC CorporationInventors: Tatsuya Sasaki, Mitsuhiro Kitamura, Kiichi Hamamoto, Shotaro Kitamura, Keiro Komatsu, Yasutaka Sakata
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Patent number: 5659565Abstract: A semiconductor mesa structure including active, absorbing, or passive guide layer is surrounding laterally by insulating mask, and is buried by a cladding layer which extends over the insulating mask, and injected current flows through the cladding layer into the mesa structure without leakage from the cladding layer into a substrate so that the semiconductor optical device is improved in performance.Type: GrantFiled: July 27, 1994Date of Patent: August 19, 1997Inventor: Shotaro Kitamura
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Patent number: 5565693Abstract: 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.Type: GrantFiled: January 7, 1994Date of Patent: October 15, 1996Assignee: NEC CorporationInventors: Tatsuya Sasaki, Mitsuhiro Kitamura, Kiichi Hamamoto, Shotaro Kitamura, Keiro Komatsu, Yasutaka Sakata
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Patent number: 5374587Abstract: In a method of manufacturing an optical semiconductor element including at least the steps of forming a mask having a stripe-like gap or interval on a semiconductor substrate, epitaxially growing a semiconductor ridge including an active layer on only an exposed gap portion of the semiconductor substrate, and epitaxially growing a semiconductor cladding layer to cover the ridge, the thickness of the active layer is substantially the same as the width of the active layer.Type: GrantFiled: July 28, 1992Date of Patent: December 20, 1994Assignee: NEC CorporationInventor: Shotaro Kitamura