Nanoscale Probing of Ultrafast Coherent Phonon Generation and Electron Diffusion in Metals
| Project/Area Number |
11305008
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| Research Category |
Grant-in-Aid for Scientific Research (A).
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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 | HOKKAIDO UNIVERSITY |
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Principal Investigator |
WRIGHT Oliver b. Hokkaido Univ.Grad.School of Eng., Prof., 大学院・工学研究科, 教授 (90281790)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUDA Osamu Hokkaido Univ.Grad.School of Eng., Asso Prof., 大学院・工学研究科, 助教授 (30239024)
TAMURA Shinichiro Hokkaido Univ.Grad.School of Eng., Prof., 大学院・工学研究科, 教授 (80109488)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥42,700,000 (Direct Cost: ¥42,700,000)
Fiscal Year 2000: ¥4,400,000 (Direct Cost: ¥4,400,000)
Fiscal Year 1999: ¥38,300,000 (Direct Cost: ¥38,300,000)
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| Keywords | Phonon / Coherent / Laser / Picosecond / Acoustics / Ultrafast / Metal / Diffusion / フェムト秒 / アモルファス / 膜厚 / 干渉計 |
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| Research Abstract |
In main aim of this study is to extend our knowledge of ultrafast acoustic phonon generation using femtosecond light pulses to basic metallic materials and nanostructures. The phonon pulse propagation dynamics in such materials and the phonon generation mechanisms can be studied. The use here of a tightly focused excitation and probe light beams a few microns in diameter allow the detection of phonons with -10 μm spatial resolution. In order to do this we have made use of an ultrafast reflectometry and interferometry for measurements at normal incidence.
We have carried out the first generation and detection of coherent phonons in amorphous and liquid metals. The results for Hg demonstrate that electron diffusion is very likely to be influencing the phonon generation. An interesting asymmetric pulse shape was observed. The first demonstration that picosecond phonon pulses could be generated and detected in an amorphous metal was also successful.
Coherent phonon generation and detection e
… More
xperiments in transition metals with -100 fs optical pulses, in particular for Cr and for Ni, shows that we can successfully model the phonon pulse shapes with the two-temperature model, taking due account of ultrasonic attenuation measured in experiment.
Ultrashort optical pulse experiments in transition metals with -10 fs optical pulses have been attempted for the first time. Using a -20 fs order optical pulse width in the infrared for both the pump and probe beams, the effect of ultrafast electron diffusion on ultrashort timescales is clearly evident in the data for a series of films of different thicknesses. A striking reversal in polarity of the signals for thicker films was observed.
Preliminary results for the generation of coherent phonon pulses in multilayer metal structures show that electron diffusion must be taken into account in order to explain the observed acoustic echoes.
Related theoretical work was successful in elucidating the way light is modulated by strain on reflection or transmission through a multilayer structure. This can be done not only for longitudinal coherent phonons but also for shear coherent phonons. Less
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Report
(3 results)
Research Products
(6 results)
