The Study of High Peak Power Ytterbium-doped Fiber Amplifier

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。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 ofommercialization 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 lasernd amplifier architecture is simple and monolithic fiber laser system is possible. For next-generation lithography-extreme ultraviolet lithography, Yb-doped fiber laser cane 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 alsomplemented. In addition to the establishment of a stable operating and application systems, I made a comparison between numerical simulation and experiment result. Ibserved 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.口試委員會審定書..........................................ii文摘要.................................................iii文摘要(Abstract)........................................iv 謝....................................................vi 錄...................................................vii目錄....................................................ix目錄................................................... xi號定義.................................................xii一章 摻鐿光纖放大器簡介..................................1 1.1 光纖放大器回顧..................................1 1.2 摻鐿光纖雷射與光纖放大器........................2 1.3 高峰值雷射光源的應用............................9 1.3.1 材料加工..................................9 1.3.2 雷射誘發電漿—極紫外光微影術.............12二章 光放大器基本原理與設計原則.........................17 2.1 光放大器基本原理...............................17 2.1.1 光與物質的交互作用.......................17 2.1.2 飽和功率以及飽和能量.....................21 2.1.3 增益介質原子能階系統.....................28 2.2 脈衝光輸出摻鐿光纖放大器設計方法...............30 2.2.1 可擷取能量之計算.........................30 2.2.2 最大高能階原子密度積分...................31 2.2.3 最佳光纖長度.............................33 2.2.4 雙纖衣光纖放大器最低重複頻率.............35 2.3 飽和放大器中的脈衝變化.........................37 2.4 放大器理論計算與模擬...........................44三章 三級光纖放大器系統介紹及元件特性量測...............52 3.1 系統架構圖.....................................52 3.2 儀器介紹及元件製作.............................53 3.2.1 雷射電流驅動器...........................53 3.2.2 光纖切割機及切割流程.....................57 3.2.3 光纖熔接機及熔接流程.....................58 3.3 元件光電特性量測...............................61 3.3.1 信號雷射光電特性量測.....................61 3.3.2 預放大幫浦雷射光電特性量測...............64 3.3.3 功率放大器幫浦雷射光電特性量測...........66 3.3.4 分波多工器光電特性量測...................67 3.3.5 光隔離器光電特性量測.....................68四章 光纖光放大器之量測結果與討論.......................70 4.1 第一級預放大器之輸出特性量測...................70 4.1.1 輸出功率.................................70 4.1.2 頻譜.....................................72 4.1.3 偏振消光係數比...........................73 4.2 實驗結果與討論.................................74 4.2.1 幫浦飽和現象.............................74 4.2.2 摻鐿濃度估算誤差.........................76 4.2.3 纖心直徑及幫浦纖心重疊積分估算誤差.......77 4.2.4 幫浦雷射吸收及輻射截面積估算誤差.........78 4.2.5 信號雷射吸收及輻射截面積估算誤差.........81 4.2.6 自發輻射壽命估算誤差.....................83 4.2.7 幫浦量子效率.............................83五章 結論與展望.........................................89amp;#63851;考文獻..................................................90錄A 鐿離子吸收及輻射截面積..............................96錄B 數值解程式碼........................................9