| Project/Area Number |
01550005
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied materials
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| Research Institution | University of Tsukuba (1990)
Chiba University (1989) |
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Principal Investigator |
KANEMITSU Yoshihiko University of Tsukuba Institute of Physics Assistant Prof, 物理学系, 講師 (30185954)
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| Project Period (FY) |
1989 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1990: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1989: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Keywords | Shock Wave / Phase Transformation / Picosecond Laser / Photoacoustic Spectroscopy / Diezoelectric Transducer / 透明トランスデュ-サ- / 光弾性法 / 表面相転移 / 高速トランスデュ-サ- / 光音響分光 |
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| Research Abstract |
1. GENERATION OF SHOCK WAVES STUDIED BY A PIEZOELECTRIC TRANSDUCER
Generation and propagation characteristics of picosecond laser-generated acoustic or shock waves in Si were studied by a ZnO transducer. In the Plasma formation region, the propagation velocity of acoustic pulses exceeds the sound velocity. At early stage of propagation. The amplitude of shock waves is affects by the formation and expansion of laser-generated plasma at the silicon surface.
2. INTENSE ACOUSTIC WAVES IN GLASS STUDIED BY AN OPTICAL METHOD
Longitudinal waves propagate at the direction of the normal to the surface plane, but shear waves propagate at about 45 to the normal. At the early stage of propagation, the velocity of the wavefront exceeds the sound velocity in glass. Moreover, it is pointed out that the generation and propagation behavior of shear waves is very sensitive to the surface conditions.
3. NEW PHOTOACOUSTIC SPECTROSCOPY USING A TRANSPARENT TRANSDUCER
We developed new photoacoustic spectroscopy system using a transparent transducer, and studied laser-induced structural changes at the surface of solids. The signal detected at the light-irradiated front surface has a large value and a good signal-to-noise ration compared with that at the back surface. Laser-induced surface structural changes are clearly observed using this system.
4. SURFACE TRANSFORMATIONS AFTER HIGH-POWER LASER IRRADIATION
Crack formation in glass surfaces and explosive crystallization in a-Si were observed after high-Zower laser irradiation. The damage in the irradiated region was caused by laser ablation and plasma formation, but cracks and liquid drops also appeared outside the irradiated region over a distance of many millimeters. Delayed crack formation is caused by chemical reactions of component of glass with atmospheric water vapor at microcracks in the surface induced by laserーdriven shock waves. We also observed explosive crystallization of aーSi initiated by shock waves.
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