- 學位論文
高峰值功率摻鐿光纖放大器之研究
The Study of High Peak Power Ytterbium-doped Fiber Amplifier
摘要
摻鐿光纖雷射及放大器相對於傳統的高峰值功率固態雷射，因為高表面積與體積比，所以散熱佳，在千瓦平均功率輸出時仍可以保持50 % 以上的光轉換效率及接近繞射極限的光束品質。因為雙纖衣光纖的發明，使幫浦雷射可以在面積較大的內纖衣中傳播，所以可以使用光束品質較差但是功率較高的半導體雷射。故可降低營運維修成本，提高商業化的可行性。未來可取代固態雷射，成為材料加工的主流。因為摻鐿光纖雷射及放大器架構簡單，整個雷射系統可全光纖化，未來可能應用在次世代微影術的極紫外光微影術，以高峰值光纖雷射誘發電漿，而產生極紫外光。因此，摻鐿光纖雷射及放大器的對於微影術重要性不言而喻。 本論文整理摻鐿光纖放大器的理論，並以 Wolfram Mathematica 6.0 完成了脈衝光及連續光的放大器模擬程式。實驗部分完成了連續輸出摻鐿光纖纖心幫浦預放大器系統、並以National Instrument LabVIEW 8.2 完成了預放大器電腦化控制系統及自動化光功率量測系統、除了建立穩定的操作及應用系統，並利用此系 統比較理論模擬以及實驗結果，觀察出纖心幫浦預放大器系統的幫浦飽和現象，討論理論中可能的變因，如摻雜濃度、信號雷射模態大小、幫浦纖心重疊積分、幫浦雷射吸收截面積及輻射截面積、信號雷射吸收截面積及輻射截面積、自發輻射壽命，一一比較後逐一排除，最後修正速率方程式，即在原方程式增加幫浦量子效率，並以模擬且討論其對輸出功率的影響並且修正理論，提出幫浦飽和的放大器系統中，幫浦量子效率對輸出功率的影響較為顯著，透過實驗歸納出幫浦量子效率的值，其值約為0.975。
並列摘要
Comparing with the traditional high peak power solid state lasers, Yb-doped fiber laser and amplifier have high surface to volume ratio for good heat dissipation. Even kW-level output power, Yb-doped fiber laser and amplifier can achieve more than 50 % optical conversion efficiency and near diffraction limit beam quality. As the invention of double cladding fiber, the pump laser can propagate in inner caldding, so low-beam quality but high-power semiconductor laser can be used. Therefore, the operation and maintenance costs can br reduced and the feasibility of commercialization is improved. Thus, solid-state laser materials processing is bound to be replaced by Yb-doped fiber laser the in the future, because Yb-doped fiber laser and amplifier architecture is simple and monolithic fiber laser system is possible. For next-generation lithography-extreme ultraviolet lithography, Yb-doped fiber laser can be emploted as high peak power source to produce plasma for generating extreme ultraviolet. Therefore, the importance of Yb-doped fiber laser and amplifier in lithography is apparent. In this thesis, I have collected some ytterbium-doped fiber amplifier theory and scripted pulsed and continuous-wave amplifier simulation program by Wolfram Mathematica 6.0. In experiment part, I finished the core-pumping pre-amplifier system and wrote a computerized control program for this system. Automatic optical power measurement program by National Instrument LabVIEW 8.2 were also implemented. In addition to the establishment of a stable operating and application systems, I made a comparison between numerical simulation and experiment result. I observed pump saturation effect of the core-pumped pre-amplifier. Several possible issues making simulation and experiment mismatch are discussed, such as doping concentration, signal laser mode diameter, pump overlap intergral, pump laser absorption crosssection and emission crosssecction, signal absorption crosssection and emission crosssection, spontaneous lifetime. Only by adopting the parameter of pumping quantum efficiency in the rate equation, the experiment result become in good agreement with the simulation. For pump saturated optical amplifier systems, pump quantum efficiency is more significant to output power, through the comparision of experiment, the pumping quantum efficiency of this system is about 0.975.