2007 Fiscal Year Final Research Report Summary
Generation and detection of picosecond shear acoustic pulses by ultra short light pulses and their application to materials physic
| Project/Area Number |
17360024
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 |
MATSUDA Osamu Hokkaido University, Grad. School of Eng., Associate Professor (30239024)
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| Co-Investigator(Kenkyū-buntansha) |
WRIGHT B. Oliver Hokkaido University, Grad. School of Eng., Professor (90281790)
TOMODA Motonobu Hokkaido University, Grad. School of Eng., Assi. Prof. (30344485)
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| Project Period (FY) |
2005 – 2007
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| Keywords | picosecond laser ultrasonics / pump-probe spectroscopy / shear acoustic waves / non-destructive testing / photoelastic effect / light scattering / anisotropy / acoustic waves in liquids |
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| Research Abstract |
Picosecond acoustic pulses can be used to study the internal structure of medium in nanometer spatial region, or the electron and lattice dynamics of medium in picosecond temporal region. Especially a method named picosecond laser ultrasonics, which uses ultra short light pulses for the generation and detection of the acoustic pulses, has been exploited to evaluate the thickness profile and elastic properties of multilayers, or to study the ultrafast dynamics of photo-induced carriers. In the previous studies, mostly the longitudinal acoustic waves have been used because of the symmetry of the system. However, the additional usage of shear acoustic waves would be favorable to extend the applicability of the method. This research aims to develop the picosecond laser ultrasonics using shear acoustic waves and to apply the method to various studies in materials physics.
The main achievements are as follows. 1) With the low symmetry surface of the anisotropic medium such as Zn and GaAs sing
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le crystals, the laser picosecond ultrasonics measurement is carried out. We develop a general light scattering theory for the inhomogeneously modulated multilayers of anisotropic medium. With this theory, the experimental results were quantitatively analyzed to retrieve the photoelastic tensor components, ultrasonic absorption coefficients, electron-phonon interaction coefficients, etc.. 2) We develop a method for the picosecond laser ultrasonics measurement in liquids. The acoustic pulses are generated at the GaAs single crystal and their propagation in water and glycerol is studied. 3) We develop a method to measure the surface displacement caused by the acoustic waves independent of the photoelastic signal. 4) We develop a theory for the acoustic wave propagation in inhomogeneous medium. 5) We develop a method to map the elastic properties of polycrystalline medium with the anisotropic acoustic wave propagation. The method is utilized to study the Cu polycrystals and the artificial phononic crystals. Less
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