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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/68424


    Title: 考慮受激拉曼散射下多模光纖脈衝雷射放大器之最大可擷取能量的數值模擬研究;Numerical Study of Maximum Extractable Energy from Multi-mode Pulsed Fiber Laser Amplifier with Considerations of Stimulated Raman Scattering
    Authors: 張宜豐;Chang,I-Feng
    Contributors: 物理學系
    Keywords: 光纖;雷射放大器;受激拉曼散射;摻鐿;可擷取能量;多橫模;數值模擬;速率-傳輸方程式;本徵值方程式;optical fiber;laser amplifier;stimulated Raman scattering;Ytterbium-doped;extractable energy;multi-transverse mode;numerical simulation;rate-propagation equation;eigenvalue equation
    Date: 2015-07-17
    Issue Date: 2015-09-23 11:33:48 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 我們利用數值方法進行高功率脈衝雷射在大模場 (large-mode-area) 光纖中隨時間演化的動態行為研究,了解受激拉曼散射 (stimulated Raman scattering) 和多橫模 (multi-mode) 對光纖脈衝雷射放大器中最大可擷取能量的影響。
    在此數值研究中,我們建構一維速率-傳輸方程式 (rate-propagation equation) 的數值模型進行光纖雷射中的輻射傳播數值模擬。在不考慮受激拉曼散射下,模擬所求得的最大可擷取能量與現有的解析理論有很好的一致性。接著,在模擬中考慮現有理論所無法處理的非線性受激拉曼散射,研究在光纖脈衝能量為最佳輸出時,種子光源必須符合的參數臨界值。為了更進一步探討多橫模效應對光纖脈衝放大器的影響,以數值積分方法求解光纖在弱導近似 (weakly-guide approximation) 下的特徵值方程式 (eigenvalue equation) 求得光纖中每支橫向模式的色散關係、等效纖芯面積 (effective core area)、以及考慮了增益介質的居量 (population) 在徑向空間變化的重疊因子 (overlapping integral) ,同時把單模假設中的速率-傳輸方程式推展到多橫模運算。最終以此程式碼估算受激拉曼散射和多橫模影響下之光纖雷射脈衝放大器中的最大可擷取能量和最佳化參數。
    模擬結果證實,在種子光源能量與脈衝寬度分別逼近臨界值時,可有效抑制受激拉曼散射的影響下,擷取出儲存在光纖雷射放大器中的最大能量。接著,在多橫模光纖雷射脈衝放大器的模擬研究中,我們發現與單橫模模型的模擬結果比較下,多橫模模型的脈衝重疊因子較小並且相對容易產生受激拉曼散射,因此需使用更大的種子光源能量與脈衝寬度來擷取出光纖雷射放大器中的最大能量。
    此研究清楚呈現大模場、高功率光纖雷射脈衝放大器最佳化的物理圖像以及量化參數條件。研究結果可直接用在實驗上設計且優化高功率、高能量脈衝光纖雷射放大器。另一方面,此多橫模、非線性的光纖雷射脈衝放大器模擬模型在未來可進一步加入不同非線性效應,用於研究大模場光纖中能量頻譜展寬的研究。
    ;A numerical study of maximum extractable energy from multi-mode pulsed fiber laser amplifier with considerations of stimulated Raman scattering is presented. Based on rate-propagation equations, a one-dimensional convection code is constructed for calculating the maximum extractable energy in fiber laser amplifiers. In order to derive the dispersion relations of fibers, the effective core area, overlapping integral with considerations of radial-dependence distribution of gain medium, and eigenvalue equations with weakly-guide approximation are also solved using the numerical approach. In the thesis, we extended the single-mode model, which is based on rate-propagation equation, to study the maximum extractable energy in fiber laser amplifiers with a large fiber core. Simulation results show that the criterions of seed energy and input seed pulse width to extract maximum energy in fiber laser amplifiers are determined by the nonlinear phenomenon and multimode effects. The numerical model used in the study can be applied to study the nonlinear effects and the spectral broadening in a large-mode-area (LMA) fiber and provide experimental designs of a practical high-power and high-energy pulsed fiber amplifier.
    Appears in Collections:[物理研究所] 博碩士論文

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