Patents by Inventor Tokuharu Kimura
Tokuharu Kimura 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: 11428864Abstract: An optical waveguide includes a core, a first cladding, a second cladding, and a heater. The first cladding configured to cover the core. The second cladding disposed over the first cladding. The heater disposed over the second cladding to heat the core. The first cladding and the second cladding are silicon oxide films. A first fixed charge density of the first cladding is lower than a second fixed charge density of the second cladding.Type: GrantFiled: June 7, 2021Date of Patent: August 30, 2022Assignee: FUJITSU LIMITEDInventor: Tokuharu Kimura
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Publication number: 20220066093Abstract: An optical waveguide includes a core, a first cladding, a second cladding, and a heater. The first cladding configured to cover the core. The second cladding disposed over the first cladding. The heater disposed over the second cladding to heat the core. The first cladding and the second cladding are silicon oxide films. A first fixed charge density of the first cladding is lower than a second fixed charge density of the second cladding.Type: ApplicationFiled: June 7, 2021Publication date: March 3, 2022Applicant: FUJITSU LIMITEDInventor: Tokuharu Kimura
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Patent number: 9948059Abstract: A semiconductor laser light source includes a semiconductor substrate formed of a first conductivity type semiconductor material, a lower cladding layer formed of the first conductivity type semiconductor material on the semiconductor substrate, a waveguide layer on the lower cladding layer, and an upper cladding layer formed of a second conductivity type semiconductor material on the waveguide layer. The waveguide layer includes a core area and rib areas thinner than the core area on either side of the core area. The core area has a quantum dot active layer, and the rib areas have no quantum dot layer. The waveguide layer forms a laser part having the core area with a constant width and a spot size converter having the core area with a taper width from a side adjacent to the laser part toward an end of the spot size converter.Type: GrantFiled: December 20, 2016Date of Patent: April 17, 2018Assignee: FUJITSU LIMITEDInventors: Tokuharu Kimura, Tsuyoshi Yamamoto, Kazumasa Takabayashi, Ayahito Uetake
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Patent number: 9698570Abstract: A quantum dot laser includes a GaAs substrate, a quantum dot active layer which has a barrier layer of GaAs and quantum dots, a GaAs waveguide core layer which is joined to the quantum dot active layer, and a lower cladding layer and an upper cladding layer which sandwich the quantum dot active layer and the GaAs waveguide core layer. The GaAs waveguide core layer extends from a front end of the quantum dot active layer and has a thickness which gradually decreases in a direction to depart from the front end of the quantum dot active layer, a refractive index of a first cladding layer is higher than a refractive index of a second cladding layer. With this structure, expansion of the optical mode diameter that is more than necessary is inhibited to prevent leakage of light, thereby obtaining sufficient optical output.Type: GrantFiled: July 8, 2016Date of Patent: July 4, 2017Assignee: FUJITSU LIMITEDInventors: Kazumasa Takabayashi, Tsuyoshi Yamamoto, Tokuharu Kimura
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Publication number: 20170104309Abstract: A semiconductor laser light source includes a semiconductor substrate formed of a first conductivity type semiconductor material, a lower cladding layer formed of the first conductivity type semiconductor material on the semiconductor substrate, a waveguide layer on the lower cladding layer, and an upper cladding layer formed of a second conductivity type semiconductor material on the waveguide layer. The waveguide layer includes a core area and rib areas thinner than the core area on either side of the core area. The core area has a quantum dot active layer, and the rib areas have no quantum dot layer. The waveguide layer forms a laser part having the core area with a constant width and a spot size converter having the core area with a taper width from a side adjacent to the laser part toward an end of the spot size converter.Type: ApplicationFiled: December 20, 2016Publication date: April 13, 2017Applicant: FUJITSU LIMITEDInventors: Tokuharu KIMURA, Tsuyoshi Yamamoto, Kazumasa Takabayashi, Ayahito Uetake
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Publication number: 20160322787Abstract: A quantum dot laser includes a GaAs substrate, a quantum dot active layer which has a barrier layer of GaAs and quantum dots, a GaAs waveguide core layer which is joined to the quantum dot active layer, and a lower cladding layer and an upper cladding layer which sandwich the quantum dot active layer and the GaAs waveguide core layer. The GaAs waveguide core layer extends from a front end of the quantum dot active layer and has a thickness which gradually decreases in a direction to depart from the front end of the quantum dot active layer, a refractive index of a first cladding layer is higher than a refractive index of a second cladding layer. With this structure, expansion of the optical mode diameter that is more than necessary is inhibited to prevent leakage of light, thereby obtaining sufficient optical output.Type: ApplicationFiled: July 8, 2016Publication date: November 3, 2016Applicant: FUJITSU LIMITEDInventors: Kazumasa Takabayashi, Tsuyoshi Yamamoto, Tokuharu KIMURA
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Patent number: 7407859Abstract: A compound semiconductor device has: a substrate; a GaN channel layer; an n-type AlqGal-qN (0<q (1) electron supply layer; an n-type GaN cap layer; a gate electrode disposed on the cap layer and forming a Schottky contact; recesses formed on both sides of the gate electrode on source and drain sides by at least partially removing the cap layer, the recesses having a bottom surface of a roughness larger than a roughness of a surface of the cap layer under the gate electrode; a source electrode disposed on the bottom surface of the recess on the source side; and a drain electrode disposed on the bottom surface of the recess on the drain side.Type: GrantFiled: October 3, 2006Date of Patent: August 5, 2008Assignee: Fujitsu LimitedInventors: Tokuharu Kimura, Toshihide Kikkawa
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Publication number: 20070026552Abstract: A compound semiconductor device has: a substrate; a GaN channel layer; an n-type AlqGal-qN (0<q (1) electron supply layer; an n-type GaN cap layer; a gate electrode disposed on the cap layer and forming a Schottky contact; recesses formed on both sides of the gate electrode on source and drain sides by at least partially removing the cap layer, the recesses having a bottom surface of a roughness larger than a roughness of a surface of the cap layer under the gate electrode; a source electrode disposed on the bottom surface of the recess on the source side; and a drain electrode disposed on the bottom surface of the recess on the drain side.Type: ApplicationFiled: October 3, 2006Publication date: February 1, 2007Applicant: FUJITSU LIMITEDInventors: Tokuharu Kimura, Toshihide Kikkawa
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Patent number: 7132699Abstract: A compound semiconductor device has: a substrate; a GaN channel layer; an n-type AlqGa1?qN (0<q?1) electron supply layer; an n-type GaN cap layer; a gate electrode disposed on the cap layer and forming a Schottky contact; recesses formed on both sides of the gate electrode on source and drain sides by at least partially removing the cap layer, the recesses having a bottom surface of a roughness larger than a roughness of a surface of the cap layer under the gate electrode; a source electrode disposed on the bottom surface of the recess on the source side; and a drain electrode disposed on the bottom surface of the recess on the drain side.Type: GrantFiled: January 27, 2004Date of Patent: November 7, 2006Assignee: Fujitsu LimitedInventors: Tokuharu Kimura, Toshihide Kikkawa
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Publication number: 20040201038Abstract: A compound semiconductor device has: a substrate; a GaN channel layer; an n-type AlqGa1-qN (0<q≦1) electron supply layer; an n-type GaN cap layer; a gate electrode disposed on the cap layer and forming a Schottky contact; recesses formed on both sides of the gate electrode on source and drain sides by at least partially removing the cap layer, the recesses having a bottom surface of a roughness larger than a roughness of a surface of the cap layer under the gate electrode; a source electrode disposed on the bottom surface of the recess on the source side; and a drain electrode disposed on the bottom surface of the recess on the drain side.Type: ApplicationFiled: January 27, 2004Publication date: October 14, 2004Inventors: Tokuharu Kimura, Toshihide Kikkawa