Dr. Hirohito Yamada Profile

Dr. Hirohito Yamada

Principal Researcher at NEC Corp

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Author

Publications (8)

Proceedings Article | 23 October 2006 Paper

Optical add-drop multiplexer with hexagonal-hole lattice PC slab waveguides

Akiko Gomyo, Jun Ushida, Masayuki Shirane, Hirohito Yamada, Tao Chu, Satomi Ishida, Yasuhiko Arakawa

Proceedings Volume 6376, 63760J (2006) https://doi.org/10.1117/12.688568

KEYWORDS: Photonic crystals, Waveguides, Reflectors, Multiplexers, Transmittance, Silicon, Crystals, Optical filters, Interfaces, Light wave propagation

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Proceedings Article | 13 October 2006 Paper

Reconfigurable optical add-drop multiplexer (R-OADM) based on silicon photonic crystal slab waveguides

Tao Chu, Hirohito Yamada, Akiko Gomyo, Jun Ushida, Satomi Ishida, Yasuhiko Arakawa

Proceedings Volume 6376, 63760I (2006) https://doi.org/10.1117/12.688125

KEYWORDS: Silicon, Photonic crystals, Waveguides, Wavelength division multiplexing, Optical switching, Multiplexers, Silicon photonics, Thermal optics, Switches, Crystals

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Proceedings Article | 6 December 2005 Paper

Optical add-drop multiplexer using PBG with hexagonal-hole lattice PC slab waveguides

Akiko Gomyo, Jun Ushida, Hirohito Yamada, Tao Chu, Satomi Ishida, Yasuhiko Arakawa

Proceedings Volume 6050, 60500B (2005) https://doi.org/10.1117/12.651989

KEYWORDS: Reflectors, Waveguides, Transmittance, Photonic crystals, Silicon, Multiplexers, Semiconducting wafers, Optical filters, Polarization, Finite-difference time-domain method

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Proceedings Article | 3 December 2005 Paper

Si-nanowire optical waveguide devices for optical communications

Hirohito Yamada, Tao Chu, Satomi Ishida, Yasuhiko Arakawa

Proceedings Volume 6019, 60192X (2005) https://doi.org/10.1117/12.637076

KEYWORDS: Waveguides, Optical components, Silicon, Polarization, Directional couplers, Integrated optics, Multiplexers, Absorption, Semiconducting wafers, Silica

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Si-nanowire waveguides are attractive structures for constructing various optical devices that are extremely small, and that can be flexibly connected as devices on a silicon (Si) wafer. The waveguides can be bent with extremely small curvatures of less than a few micrometers of bending radius because the large difference of refractive indices between the Si-core (n = 3.5) and the silica cladding material (n = 1.5) strongly confines the optical power in the waveguide core. Therefore, these waveguides are promising for flexible optical interconnections on Si chips as well as for constructing many extremely small optical devices. We used Si-nanowire waveguides to fabricate optical directional couplers and demonstrated their fundamental characteristics. Their coupling-length was extremely short, several micrometers, because of strong optical coupling between the waveguide cores. Therefore, we could construct ultra compact power combiners/dividers. We have also demonstrated wavelength demultiplexing functions for these devices with a long coupled waveguide. Optical outputs from a device with a 100-μm long coupled waveguide changed reciprocally with 20-nm wavelength spacing between the parallel and cross ports. Ultra small optical add-drop multiplexers (OADMs) with Bragg grating reflectors made of the Si-nanowire waveguides have been also demonstrated. The dropping wavelength bandwidth of the OADMs was less than 0.7 nm, and these dropping wavelengths could be precisely designed by adjusting the grating period, and this indicated the possibility of applying these devices in dense WDM systems. Using the Si-nanowire waveguide, we have also demonstrated nonlinear-optic effects such as the spectral broadening of optical short pulses due to self-phase modulation and nonlinear transmittance based on two-photon absorption. At a 12 W input power level, we observed a 1.5-π nonlinear phase shift as well as strong saturation of optical output power from a 4-mm Si-nanowire waveguide sample, and that indicates the possibility of constructing integrated nonlinear-optic wavelength conversion devices or optical limiters with Si-nanowire waveguides.

Proceedings Article | 9 July 2004 Paper

Control of light propagation and localization in a photonic crystal slab by using a micromechanical actuator

Satoshi Iwamoto, Hirohito Yamada, Akiko Gomyo, Masayuki Shirane, Yasuhiko Arakawa

Proceedings Volume 5360, (2004) https://doi.org/10.1117/12.528752

KEYWORDS: Waveguides, Transmittance, Actuators, Modulation, Semiconductors, Photonic crystals, Refractive index, Light wave propagation, Optical switching, Microelectromechanical systems

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Proceedings Article | 11 July 2002 Paper

Micro-lightwave circuits based on photonic crystal

Hirohito Yamada, Masatoshi Tokushima, Masayuki Shirane

Proceedings Volume 4870, (2002) https://doi.org/10.1117/12.475548

KEYWORDS: Photonic crystals, Waveguides, Silicon, Optical switching, Channel waveguides, Switching, Finite-difference time-domain method, Optical filters, Photonic integrated circuits, Directional couplers

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Proceedings Article | 12 November 1999 Paper

Precisely frequency-controlled mode-locked laser diode for all-optical clock extraction at 40 GHz SDH frequency

Ichiro Ogura, Hisakazu Kurita, Tatsuya Sasaki, Hirohito Yamada, Hiroyuki Yokoyama

Proceedings Volume 3795, (1999) https://doi.org/10.1117/12.370156

KEYWORDS: Clocks, Mode locking, Semiconductor lasers, Picosecond phenomena, Refractive index, Optical clocks, All optical signal processing, Absorption, Distributed Bragg reflectors, Ultrafast phenomena

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Proceedings Article | 2 May 1997 Paper

Partially corrugated waveguide laser diodes for use in CATV networks

Hirohito Yamada, Tetsuro Okuda, Yidong Huang, Yoshiharu Muroya, Toshitaka Torikai

Proceedings Volume 3001, (1997) https://doi.org/10.1117/12.273812

KEYWORDS: Distortion, Capacitance, Intermodulation, Modulation, Resistance, Light sources, Waveguide lasers, Diodes, Circuit switching, Active optics

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Showing 5 of 8 publications

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