K. Ueda

Research Field

A solid-state laser material based on highly transparent cubic Nd3+:Lu2O3 ceramic was developed using nanocrystalline technology and a nonpress vacuum sintering method. Spectroscopic properties of this ceramic laser material were investigated. At room temperature under single-laser diode pumping, efficient continuous wave laser oscillation was demonstrated at two wavelengths of the 4F3/2→4I11/2 channel. The potential application of such a laser material was also discussed.

Nanocrystalline material

Solid-state laser

Selective laser sintering

Continuous wave

10.1063/1.1527234

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Citations (183)

Quasi-Phase-Matched Second-Harmonic Generation in a Periodic-Lens Sequence Waveguide with a Relatively Wide Wavelength-Tuned Width

Japanese Journal of Applied Physics (1995)

Y. Yamamoto Satoshi Yamaguchi Noriko Yamada K. Ueda Takahiro Matsumoto

The phase-matching characteristic of a quasi-phase-matched second-harmonic generation in a periodic-lens sequence waveguide on z -face KTiOPO 4 (potassium titanyl phosphate) crystal was obtained by measuring, as a function of input optical wavelength, the intensity of frequency-doubled radiation. The fabricated waveguide is a kind of segmented domain-inverted waveguide of which grating pitch is 4 µ m. The phase-matching was observed in the fundamental wavelength region of 850-860 nm. The half-width of the peak around 854 nm is about 0.3 nm. The broadening of phase-matching in wavelength was explained using geometrical optics.

Waveguide

Potassium titanyl phosphate

10.1143/jjap.34.6382

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Citations (0)

Spin Filter Effect of La0.7Sr0.3MnO3/Bi1-xBaxFeO3 Junctions

Journal of the Magnetics Society of Japan (2010)

S. Kobayashi S. Tachiki K. Yoshimoto Y. Sugimoto Y. Takeda

Spin-filter devises were fabricated using multiferroic Bi1-xBaxFeO3 films. La1-xSrxMnO3/Bi1-xBaxFeO3/LaNiO3 junctions showed non-linear current-voltage characteristics with barrier height of 0.37eV and magnetoresistance (MR) of 2.3% at 4.2 K. These results indicate ultra-thin Bi1-xBaxFeO3 layers behaved as ferromagnetic tunnel barriers and showed spin-filter effects. From the analysis of the temperature dependence of current-voltage characteristics of the junctions and the leakage current of Bi1-xBaxFeO3 layers, one of possible reasons for low MR is suppression of spin-filter effects by tunneling through defect levels induced by O and/or Bi deficiency in Bi1-xBaxFeO3 tunnel barriers.

Leakage (economics)

Biasing

10.3379/msjmag.1006r005

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Ambipolar transport and modulation of electronic properties of Mn<sub>2</sub>CoAl films by ionic liquid gating

Extended Abstracts of the 2020 International Conference on Solid State Devices and Materials (2017)

K. Ueda Shingo Hirose Masaaki Mori Hayato Asano

Ambipolar diffusion

Modulation (music)

10.7567/ssdm.2017.k-8-04

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24aPS-29 Additivity of magnetic domain wall velocities induced by current and field

Meeting abstracts of the Physical Society of Japan (2012)

Takeshi Koyama K. Ueda Daichi Chiba Shunsuke Fukami N. Ishiwata

Additive function

Source

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Fabrication of epitaxial Co2MnSi films on lattice-matched MgAl2O4 substrates by ion-beam assisted sputtering

Thin Solid Films (2014)

K. Ueda M. Nishiwaki T. Soumiya H. Asano

Lattice (music)

10.1016/j.tsf.2014.09.045

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Citations (3)

High-pressure and high-temperature annealing effects of boron-implanted diamond

Diamond and Related Materials (2008)

K. Ueda Makoto Kasu

10.1016/j.diamond.2007.12.017

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Citations (25)

New results on characterization of highly transparent C-modification Lu₂O₃ nanocrystalline ceramics: room-temperature tunable CW laser action of Yb³⁺ ions under LD-pumping and the propagation kinetics of non-equilibrium acoustic phonons

Laser Physics Letters (2006)

Alexander A. Kaminskii S.N. Bagayev K. Ueda K. Takaichi A. Shirakawa

We report on the first achievement of CW oscillation in Yb 3+ :Lu 2 O 3 ceramic lasers ( 2 F 5/2 → 2 F 7/2 channel) under LD-pumping at 0.976 μm wavelength, as well as present of the thickness of grain boundary layers in Lu 2 O 3 ceramics was estimated under non-equilibrium acoustic phonon propagation kinetics at helium temperature (2.4–3.8 K).

Nanocrystalline material

10.1002/lapl.200610026

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Citations (35)

High RF output power for H-terminated diamond FETs

Diamond and Related Materials (2006)

Makoto Kasu K. Ueda Haitao Ye Y. Yamauchi Satoshi Sasaki

Power gain

Maximum power principle

10.1016/j.diamond.2005.12.025

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Citations (70)