| Project/Area Number |
14350380
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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 |
Material processing/treatments
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| Research Institution | Nagaoka University of Technology |
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Principal Investigator |
ITO Yoshiro Nagaoka University of Technology, Department of Mechanical Engineering, Professor, 工学部, 教授 (60176378)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥14,000,000 (Direct Cost: ¥14,000,000)
Fiscal Year 2004: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 2003: ¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2002: ¥8,000,000 (Direct Cost: ¥8,000,000)
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| Keywords | femtosecond laser / laser ablation / time-resolved imaging / ultra-fast phenomena / shadowgraph / transient stress / 過渡応力 / フェトム秒レーザー / レーザー加工プロセス / シャドーグラフ / ガラス / ポンプ-プローブ法 |
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| Research Abstract |
Materials processing by ultra-fast lasers have become new, attractive methods in laser materials processing. The processes, are, however, not clear enough to understand these futures.
In this study, an ultra-fast imaging system has been developed for a study on femtosecond laser processes of several kinds of materials, such as metal, metal film, semi-conductor and dielectrics. The system developed is a kind of pump-probe systems. Out put of a second harmonic generator contains both the fundamental and the second-harmonic wavelength light : the fundamental light is used as a pump pulse and the second harmonics light as a probe pulse. Time interval between these two pulses is changed by optical delay lines and images illuminated by probe pulses are taken by a CCD camera. Series of images taken at different time interval reveal time dependence of ultra-fast laser processing. The observation geometry of the system can change between two modes: side-looking and surface looking modes.
Observed images in side-looking mode show laser-induced plumes propagating into air from 2 to 9 ns after laser irradiation. From the change of the position of the front of the plume at constant time with pulse number suggest that the ablation rates at initial stage are constant and are greatest for glass substrate and smallest for aluminum. Observed images in the surface-looking mode suggest that there is a significant time delay between the pump pulse and the appearance of observable change at the irradiated position.
In addition, a time-resolved observation method of laser-induced transient stress field has been developed to study the fast laser processing in details. The method utilizes a nano-second pulse laser as a probe pulse and photoelasticity methods as a principle of visualization of the stress field. Using this system, laser-induced stress fields in epoxy-resin blocks from 100 to 2000 ns after laser irradiation are successfully visualized.
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