| Project/Area Number |
15340132
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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 |
原子・分子・量子エレクトロニクス・プラズマ
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
SHIRAKAWA Akira The University of Electro-Communications (UEC), Institute for Laser Science, Assistant Prof., レーザー新世代研究センター, 助手 (00313429)
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| Co-Investigator(Kenkyū-buntansha) |
UEDA Ken-ichi UEC, Institute for Laser Science, Prof., Director, レーザー新世代研究センター, 教授 (10103938)
MUSHA Mitsuru UEC, Institute for Laser Science, Assistant Prof., レーザー新世代研究センター, 助手 (40303028)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 2003: ¥11,300,000 (Direct Cost: ¥11,300,000)
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| Keywords | Coherent array / Coherent beam combining / Fiber laser / Power scaling / Complex resonator / Single-frequency fiber laser / Coherent control of beam direction / Harmonic mode-locking / 高調波モード同期 |
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| Research Abstract |
We have proposed and demonstrated highly efficient coherent beam combining of fiber lasers and laser diodes by Y-shaped array coupled with fused fiber couplers. Near-field coupling of N fiber lasers by use of N×N fused fiber couplers enables a power-summed output from one of N fiber ports without any fiber-length adjustment. The wavelengths satisfying constructive interference have the highest effective reflectivities and are selectively excited as a coherently-added single beam output. High addition efficiencies of 94, 96, and 85% have been obtained for N=2, 4, and 8 erbium-doped fiber lasers, respectively. The measured frequency characteristics of the coupled array well matched with the theory. The measured array-number dependence of the addition efficiency is well matched with the simple-scaling theory we developed. The clarified limit of coherent addition (N=8〜10) is found to be an inherent problem in length-different laser arrays. The characteristic bandwidth narrowing by the Vernier effect can be applied to high-power, narrowband fiber laser beyond nonlinearity limitations. By threshold control of the supermodes, high-speed (>1 kHz), high-contrast-ratio (>100) coherent control of beam direction has been demonstrated. We also proposed that harmonic mode locking can be attained by coupling ultrafast lasers. In a preliminary experiment, 20-th harmonic sub-picosecond pulse train with >40-dB mode suppression ratio has been successfully obtained. In conclusion, it has been shown that coherent arraying of multiple lasers realizes not only power and brightness scaling but various new-functionality lasers.
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