Papers - HAMANAKA Yasushi
-
Electron dynamics and surface plasmon resonance nonlinearities in metal nanoparticles Reviewed
N. Del Fatti, F. Vallee, C. Flytzanis, Y. Hamanaka, and A. Nakamura
Chemical Physics 251 215 - 226 2000.04
Language：English Publishing type：Research paper (scientific journal)
-
E. Frankevich, H. Ishii, Y. Hamanaka, T. Yokoyama, A. Fuji, S. Li, K. Yoshino, A. Nakamura, and K. Seki
Physical Review B 62 2505 - 2515 2000.04
Language：English Publishing type：Research paper (scientific journal)
-
Dispersion of third-order nonlinear optical susceptibility of silver nanocrystal-glass composites Reviewed
Y. Hamanaka, N. Hayashi, A. Nakamura, and S. Omi
Journal of Luminescence 87-89 859 - 861 2000.04
Language：English Publishing type：Research paper (scientific journal)
-
Dispersion of third-order nonlinear optical susceptibility of silver nanocrystal-glass composites Reviewed
Y. Hamanaka, N. Hayashi, A. Nakamura, S. Omi
Journal of Luminescence 87 859 - 861 2000
Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Science Publishers B.V.
We have investigated dispersion of third-order nonlinear optical susceptibility, χ(3), for a silver nanocrystal-glass composite around the surface plasmon resonance band. A real and an imaginary part of χ(3) have been separately measured by a Z-scan method. The maximum value of imaginary χ(3) is -1.5 × 10-10 esu at 2.97 eV and the real χ(3) value ranges from -4.4 × 10-11 to +4.4 × 10-11 esu. We have calculated dispersion curves of the composite assuming that the real and imaginary parts of dielectric constant of metal nanocrystals are changed due to the creation of hot electrons by optical excitation. The dispersion curves near the surface plasmon band show features characteristic of the composite system, which is not described by a two-level atomic model.
-
Formation of polaron pairs and time-resolved photogeneration of free charge carriers in-conjugated polymers Reviewed
Eugene Frankevich, Hisao Ishii, Yasushi Hamanaka, Takahiro Yokoyama, Akihiko Fuji, Sergey Li, Katsumi Yoshino, Arao Nakamura, Kazuhiko Seki
Physical Review B - Condensed Matter and Materials Physics 62 ( 4 ) 2505 - 2515 2000
Language：English Publishing type：Research paper (scientific journal)
We have performed in the present work time-resolved experiments on poly(3-dodecyl-thiophene) (P3DDT) and poly(2,5-dioctyloxy-(Formula presented)-phenylene vinylene) (OO-PPV) films by directly probing the formation of charge carriers responsible for the cw photoconductivity within the time domain of -10 ps to 1 ns. Laser light pulses of 400 nm wavelength, 150 fs width, induced photoconductivity in a sample with a frequency 1 kHz. Red 800 nm light pulses delayed in respect to blue ones were revealed to affect the photoconductivity. The effect of the second pulses increased with the delay time. Red light induced changes of the photoconductivity were positive in OO-PPV, and negative in P3DDT. These results are rationalized as an evidence of delayed not immediate formation of free charge carriers. The carriers seem to be formed within 10 ps after the pumping pulse. A mechanism of formation of free polarons from polaron pair is suggested, which has permitted to explain main feature of the results including different signs of the effect of the red light in different polymers. © 2000 The American Physical Society.
-
Linear and nonlinear optical response in metal nanocrystal-doped glasses Reviewed
A. Nakamura, Y. Hamanaka, and S. Omi
Bulletin of Cluster Science and Technology 2 17 - 23 1999.04
Language：Japanese Publishing type：Research paper (scientific journal)
-
A facile sol-gel method for the encapsulation of gold nanoclusters in silica gels and their optical properties Reviewed
S. Tamil Selvan, M. Nogami, A. Nakamura, and Y. Hamanaka
Journal of Noncrystalline Solids 255 254 - 258 1999.04
Language：English Publishing type：Research paper (scientific journal)
-
Multiphoton Reduction of Eu3+ to Eu2+ in methanol using intense, short pulses from a Ti:sapphire laser Reviewed
N. Nakashima, S. Nakamura, S. Sakabe, H. Schillinger, Y. Hamanaka, C. Yamanaka, M. Kusaba, N. Ishihara, and Y. Izawa
Journal of Physical Chemistry A 103 3910 - 3916 1999.04
Language：English Publishing type：Research paper (scientific journal)
-
Hot carrier relaxation dynamics in In0.53Ga0.47As studied by femtosecond pump-probe spectroscopy Reviewed
D. Nishiwaki, Y. Hamanaka, Y. Nonogaki, Y. Fujiwara, Y. Takeda, and A. Nakamura
Journal of Luminescence 83&84 49 - 53 1999.04
Language：English Publishing type：Research paper (scientific journal)
-
Femtosecond relaxation dynamics of hot carriers in photoexcited In0.53Ga0.47As Reviewed
Y. Hamanaka, D. Nishiwaki, Y. Nonogaki, Y. Fujiwara, Y. Takeda, and A. Nakamura
Physica B 272 391 - 393 1999.04
Language：English Publishing type：Research paper (scientific journal)
-
Ultrafast response of nonlinear refractive index of silver nanocrystals embedded in glass Reviewed
Y. Hamanaka, A. Nakamura, S. Omi, N. Del Fatti, F. Vallee, and C. Flytzanis
Applied Physics Letters 75 1712 - 1714 1999.04
Language：English Publishing type：Research paper (scientific journal)
-
Hot carrier relaxation dynamics in In<inf>0.53</inf>Ga<inf>0.47</inf>As studied by femtosecond pump-probe spectroscopy Reviewed
D. Nishiwaki, Y. Hamanaka, Y. Nonogaki, Y. Fujiwara, Y. Takeda, A. Nakamura
Journal of Luminescence 83-84 49 - 53 1999
Language：English Publishing type：Research paper (scientific journal)
We have investigated relaxation dynamics of hot carriers and formation dynamics of excitons in an In0.53Ga0.47As thin film at 4.2 and 77 K by means of femtosecond pump and probe spectroscopy. The spectral change of exciton absorption band induced by the pumping pulse is composed of broadening and peak shift. The broadening is attributed to scattering of excitons created around the Γ point by the probe pulse with free carriers generated by the pumping pulse. The observed blue and red shifts are ascribed to the exciton-exciton exchange interaction and the band-gap renormalization, respectively. The time evolution of the shifts of the order of 30 ps is interpreted in terms of the energy-loss processes of hot carriers with emission of optical phonons. Comparison of the observed decay behaviors with the theoretical calculation, taking into account the Frohlich interaction, indicates a reduction in the carrier cooling rate by a factor of 40 in highly excited In0.53Ga0.47As. © 1999 Elsevier Science B.V. All rights reserved.
-
Ultrafast relaxation dynamics of electrons in silver nanocrystals embedded in glass Reviewed
Y. Hamanaka, N. Hayashi, A. Nakamura, and S. Omi
Journal of Luminescence 76&77 221 - 225 1998.04
Language：English Publishing type：Research paper (scientific journal)
-
Surface plasmon resonance dynamics in silver nanoparticles Reviewed International coauthorship International journal
N. Del Fatti, F. Vallee, C. Flytzanis, Y. Hamanaka, A. Nakamura, and S. Omi
OSA Technical Digest 7 93 - 94 1998
Language：English Publishing type：Research paper (international conference proceedings)
-
Ultrafast relaxation dynamics of electrons in silver nanocrystals embedded in glass Reviewed
Y. Hamanaka, N. Hayashi, A. Nakamura, S. Omi
Journal of Luminescence 76-77 221 - 225 1998
Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier
Relaxation dynamics of excited electrons in silver nanocrystals with average radii of 3.0 and 4.9 nm embedded in glass has been investigated by femtosecond pump and probe spectroscopy. The surface-plasmon band shows both broadening and red shift with excitation by 200 fs laser pulses. Time response exhibits a two-component decay, and the decay times of the fast and slow components are 2-3 ps and ∼ 200 ps, respectively. Time evolution of the nonlinear absorption due to surface-plasmons reflects a cooling process of hot electrons through the electron-phonon interaction. The additional broadening is ascribed to the increase of surface-plasmon damping due to nonequilibrium heating of electrons. When an absolute value of a dielectric constant of silver nanocrystals is decreased with the femtosecond pulse excitation, the surface-plasmon resonance shows a red shift. We demonstrate time response of nonlinear refractive index on the picosecond time scale. © 1998 Elsevier Science B.V. All rights reserved.
-
Picosecond dynamics of intramolecular charge-transfer processes of beta-substituted porphyrins adsorbed on the porous glass Reviewed
S. Kotani, H. Miyasaka, A. Itaya, Y. Hamanaka, N. Mataga, S. Nakashima and A. Osuka
Chemical Physics Letters 269 274 - 280 1997.04
Language：English Publishing type：Research paper (scientific journal)
-
Raman scattering of iodine intercalated C60 crystals Reviewed
S. Nakashima, M. Norimoto, H. Harima, Y. Hamanaka, L. S. Grigoryan and M. Tokumoto
Chemical Physics Letters 268 359 - 364 1997.04
Language：English Publishing type：Research paper (scientific journal)
-
Temperature dependence of Raman scattering in vapour-grown C60 crystals Reviewed
Y. Hamanaka, M. Norimoto, S. Nakashima, and M. Hangyo
Journal of Physics: Condensed Matter 7 9913 - 9924 1995.04
Language：English Publishing type：Research paper (scientific journal)
-
Raman scattering of solution-grown and vacuum-deposited C60 crystals Reviewed
Y. Hamanaka, M. Norimoto, S. Nakashima, and M. Hangyo
Chemical Physics Letters 233 590 - 596 1995.04
Language：English Publishing type：Research paper (scientific journal)
-
Temperature dependence of Raman scattering in vapour-grown C60 crystals Reviewed
Y. Hamanaka, M. Norimoto, S. Nakashima, M. Hangyo
Journal of Physics: Condensed Matter 7 ( 50 ) 9913 - 9924 1995
Language：English Publishing type：Research paper (scientific journal)
The temperature dependence of the Raman spectra of vapour-grown C 60 crystals is investigated with deep-red excitation. The excitation using a deep-red laser can avoid a photo-induced transformation of C 60 crystals during the Raman measurement. It is found that discontinuous changes occur in the Raman spectra at the SC-FCC phase transition temperature (260 K). Most intramolecular vibrational modes broaden drastically as the temperature exceeds 260 K. Crystal-field splitting of the intramolecular vibrational modes is observed below 260 K. The broadening of the Raman bands would be caused by the increase in the inhomogeneity of intermolecular force fields in the FCC phase. This broadening corresponds to the increase in the orientational disorder of C60 molecules above the phase transition.
