全光纖百瓦級連續輸出摻鐿光纖雷射及其直接倍頻應用

光纖雷射相對於傳統高功率雷射，可以提供更高的光轉換效率以及更接近繞射極限的光束品質，加上光纖型態的增益介質為輕薄短小，散熱性能好，從商業角度切入可以大幅降低營運和維修成本，未來更有很大的希望取代傳統高功率雷射在雷射加工、非線性光學應用、以及雷射電漿物理上的應用。另外針對光纖雷射未來的發展，除了已經擁有單模態數連續輸出千瓦等級的輸出，多模態也可以達到數十千瓦的門檻外，脈衝等級的光纖放大器也逐漸發展成熟。在本論文中，成功的產生將近百瓦等級的高功率摻鐿光纖雷射，並且成功的和模擬軟體相對應，光轉換效率超過50%，而且出輸的光束品質M2為1.22，提供一個穩定的基頻光源適合來做直接倍頻實驗。另外也探討了雙折射相位匹配晶體的優劣，選用三酸硼鋰晶體來做二倍頻產生的非線性晶體，並且深入討論其相位匹配的條件以及在聚焦條件下的高斯光束，其最優化的二倍頻效率產生情形，並且比對了實驗值與最佳的聚焦條件，確實可以得到最好的二倍頻功率輸出，而且產生的連續輸出綠光功率可以至少維持一小時300毫瓦，光束品質M2為1.76，提供一個相當不錯的直接倍頻實驗平台。

關鍵字

摻鐿光纖雷射；二倍頻；三酸硼鋰晶體

並列摘要

In comparison with the traditional high power lasers, fiber lasers provide several advantages, such as extremely high optical conversion efficiency and better beam quality which is closed to the diffraction limit. From the aspects of compactness and heat dissipation, the usage of the active fiber has a great commercial potential, which can reduce the operating cost and maintenance fee. For the applications of manufacturing, nonlinear optics and laser plasma, it has a great possibility to replace the traditional high power laser. For the progress of the fiber laser, thousands watts of single mode continuous wave (CW) output power has already existed. Besides, the multi-mode fiber laser has achieved the level of ten thousands of watts, and the pulse fiber amplifier is gradually on the progress. In this thesis, a nearly hundred-watt-level ytterbium fiber laser is demonstrated, and the experimental data agree well with the simulation result. The optical conversion efficiency is over 50%, and the beam quality factor is 1.22, which is a stable laser source, being suitable for the direct second harmonic generation (SHG). Furthermore, there is a discussion about the birefrigent phase matching condition and the choice of LiB3O5 as the nonlinear crystal for the SHG. Under the condition of focused Gaussian beam, there exists an optimized solution to fit the SHG conversion efficiency. In addition, through the experiments, it is proved that the theoretically optimized focusing condition has the greatest CW SHG output power. Moreover, the CW SHG power is stable to maintain at least 300 mW for an hour, with the beam quality factor closed to 1.76. All the experimental data had convinced that the ytterbium fiber laser is a good platform for direct frequency doubling.

並列關鍵字

Ytterbium-doped fiber laser ； SHG ； LiB3O5

參考文獻

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[3] S. Konno, T. Kojima, S. Fujikawa, and K. Yasui, “High-brightness 138-W green laser based on an intracavity-frequency-doubled diode-side-pumped Q-switched Nd:YAG laser,” Opt. Lett. 25 (2), pp. 105-107 (2000).

[4] Liu, M. A. Norsen, R. D. Mead, "120 W, linearly-polarized single-mode Yb-doped fiber laser and 60 W green by SHG," Proc. of SPIE 5709, pp. 45-52 (2005).

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全光纖百瓦級連續輸出摻鐿光纖雷射及其直接倍頻應用

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