| Project/Area Number |
11555182
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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 | 展開研究 |
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| Research Field |
Material processing/treatments
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
KONDO Ken-ichi Tokyo Institute of Technology, Materials and Structures Laboratory, Professor, 応用セラミックス研究所, 教授 (50111670)
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| Co-Investigator(Kenkyū-buntansha) |
TAKENAKA Hisataka NTT Advanced Technology Inc., Research team leader, 材料開発・分析センター, 研究職
HIRONAKA Yoichiro Tokyo Institute of Technology, Materials and Structures Laboratory, Research Associate, 応用セラミックス研究所, 助手 (20293061)
NAKAMURA Kazutaka g. Tokyo Institute of Technology, Materials and Structures Laboratory, Associate Professor, 応用セラミックス研究所, 助教授 (20302979)
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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 |
¥13,500,000 (Direct Cost: ¥13,500,000)
Fiscal Year 2000: ¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 1999: ¥8,000,000 (Direct Cost: ¥8,000,000)
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| Keywords | femtosecond laser / laser machining / dielectric breakdown / ceramics / tera watt laser / optical communication device / precise machining / shock wave |
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| Research Abstract |
In the first year, a set of precise stages for controlling a target position at five-axes were installed in the large vacuum chamber which was a part of the femtosecond, terawatt laser system. Some preliminary tests of machining were carried out in order to find a critical condition for dielectric breakdown in silicon crystal.The threshold laser fluence was 0.4 J/cm^2 for ablation in the case of a pulse width of 300 ps and was in good agreement with the extrapolation of the published data. The threshold fluence decreased under atmospheric condition. By changing energy of femtosecond laser at a pulse width of 50 fs, values of ablation threshold were experimentally examined for several ceramic materials such as fused quartz, optical glass(BK-7), alumina crystal, and calcium fluoride crystal. Threshold values for alumina crystal were analyzed by three methods as follows : (1) monitoring the scattered light from the sample surface, (2) gaussian fitting of laser energy spatial distribution to the crater shape of sample, and (3) fitting of the etching rate to the formula for five-photons absorption mechanism. They were in good agreement each other as follows : (1) 0.35, (2) 0.37, and (3) 0.37 J/cm^2, respectively. Such values were dependent on materials but did not reveal a simple linear relationship with magnitude of their bad gap. Calcium fluoride crystal was broken by the effect of thermalstress and/or shock waves that were generated after the irradiation of laser, because the crystal had a weak mechanical strength. A trial machining were carried out for patterning of some mask patterns such as character and designed mark. Sharp edges were obtained in the direction of the depth, but interference of laser light deformed the pattern. It requires modifying optical system without parabolic mirror. In conclusion, this femtosecond laser machining technology is promising that ceramics having a certain strength can be machined precisely without thermal damage.
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