1989 Fiscal Year Final Research Report Summary
Femtosecond relaxation dynamics of excitons localized by disorder in semiconductors
| Project/Area Number |
63460021
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Hokkaido University |
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Principal Investigator |
MINAMI Fujio Hokkaido University, Research Institute of Applied Electricty, Associate Professor, 応用電気研究所, 助教授 (30200083)
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| Co-Investigator(Kenkyū-buntansha) |
ASAKA Shuji Hokkaido University, Research Institute of Applied Electricity, Instructor, 応用電気研究所, 助手 (00167876)
ASAKA Shuji Hokkaido University, Research Institute of Applied Electricity, Instructor (00167876)
ASAKA Shuji Hokkaido University, Research Institute of Applied Electricity, Instructor (00167876)
ASAKA Shuji Hokkaido University, Research Institute of Applied Electricity, Instructor (00167876)
ASAKA Shuji Hokkaido University, Research Institute of Applied Electricity, Instructor (00167876)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Femtosecond Spectroscopy / Localized exciton / Phase relaxation / Diamond anvil cell / GaAs / AlAs superlattices / Temporally Incoherent light / Layered compound |
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| Research Abstract |
1) We made a passively mode-locked dye laser system. The dye laser produces a train of 100 fs pulses at the rate of 100 MHz. The wavelength tuning range is 580-620 nm.
2) The phase relaxation time of the exciton in GaSe was measured by using temperature-dependent photon echo method. It is found that the optical dephasing is caused by phonon scattering above 30 K.
3) A close correlation was found between the radiative lifetime and the phase correlation time of the free excitons in GaSe. This result gives a direct experimental proof of the recent theoretical prediction.
4) We made two different hole burning experiments in the free exciton line in GaSe: pulse propagation delay and pump-probe experiments. Both results support arguments for partial exciton localization by stacking disorder.
5) We proposed two new methods to investigate femtosecond processes: pump-probe and upconversion methods using temporally incoherent lights.
6) Temporal behavior of hot carriers in CdSe was investigated with subpicosecond accuracy, by using a novel pump-probe technique. in which the self-phase modulation effect in an optical fiber is utilized to extend the spectral width of the probe pulse. Pump-induced changes is explained by the formation of an electron-hole plasma and a succeeding thermal relaxation of the plasma.
7) Photoluminescence spectra of short-period GaAs/AlAs superlattices were studied as a function of hydrostatic and uniaxial pressure at 20 K. It is found that lowest excited state is an indirect exciotns at Xz.
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