| Project/Area Number |
16560034
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied optics/Quantum optical engineering
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| Research Institution | Nagaoka University of Technology |
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Principal Investigator |
UCHIKI Hisao Nagaoka University of Technology, Faculty of Engineering, Professor, 工学部, 教授 (50142237)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Kunihiko Nagaoka University of Technology, Faculty of Engineering, Assistant Professor, 工学部, 助手 (30334692)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Keywords | calcium thiogallate / excited state absorption / 光利得 / レーザ |
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| Research Abstract |
Ce-doped CaGa_2S_4 crystals were excited by a pulsed dye laser with a wavelength of 425 nm and a pulse duration of 1 ns. A saturation of photoluminescence (PL) intensity from the crystals was observed under high density excitation. Five-level model taking account of excited state absorption was proposed and the PL intensity saturation was analyzed by the model. The cross-section of the excited state absorption at 425 nm obtained from the analysis was of the order of 1×10^<-16> cm^2 much larger that the ground state absorption cross-section of 2×10^<-18> cm^2 at 425 nm. This larger excited state absorption is a major problem for an application of Ce-doped CaGa_2S_4 crystals to a laser gain medium. A pump-probe gain/loss spectroscopy was conducted next. A ns pulsed dye laser with a wavelength of 425 nm and a pulse energy of 50 μJ was used as a pump and a ns pulsed dye laser with a wavelength of 460 to 600 nm and a pulse energy of 5 μJ was used as a probe. A negative gain or loss was observed. The excited state absorption at 500 nm was 8×10^<-17> cm^2 which was about one order of magnitude larger than the stimulated cross-section of 6×10^<-18> cm^2. The loss had a decay time of 18 ns as a function of the delay time of the probe, which should be the lifetime of the excited state of 36 ns from the five-level model. This discrepancy has not been resolved yet.
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