本論文將以數值模擬的方式模擬出Q切換脈衝並設計出一摻鐿全光纖式Q切換脈衝雷射系統。由於市售單模雷射輸出功率最多500mW，製作高功率脈衝雷射仍嫌不足，因此本文雷射系統架構將採用多模雷射並將光耦合進入雙披覆層光纖，藉此輸出高功率雷射，而系統中會加入摻鐿之可飽和吸收體光纖來產生脈衝雷射，並利用增益切換來將可飽和吸收體光纖迅速恢復初始吸收值以便進行產生下一個Q切換脈衝。本文中將會推導出一組雙波長光子雷射方程式以便用來模擬分析光子在雷射系統中隨增益居量及吸收居量的變化，並探討輸入幫浦能量、可飽和吸收體初始吸收值、第一共振腔長度及第一共振腔反射率的變化對脈衝雷射之脈衝重複率、脈衝能量、脈衝寬度、脈衝功率峰值所產生的影響。而在實驗上，我們會建置一個被動式全光纖Q切換脈衝雷射系統，並量測其脈衝輸出。此外，也會透過更換飽和吸收體光纖的長度，給予系統不同的初始吸收值，並藉此了解元件參數的改變對脈衝輸出特性的影響，以便為日後脈衝雷射系統的最佳化提供一個較明確的方向

This thesis focused on simulation of Q-switched pulsed laser and implement the passively all- Yb+3fiber Q-switched pulsed laser at high peak power using mode-field area mismatch method in dual cavity. Since the output power of single-mode laser diode is too low，we use multi-mode laser and cladding pumped laser system to boost the output power of laser system and achieve the high power Q-switched all-fiber laser system. We also derive some theories about mode-field mismatch method and rate equations about dual cavity. Based on the outcome in the chapter2，we establish a numerical model to simulate a Q-switched pulse. In the simulation，we get a Q-switched pulse with an energy of 38.64 μJ、a width of 32.83 ns and a peak power of 975W. Moreover, the performance of pulses can be improved by replacing the longer SAQS fiber in the experiment. The tendency observed in the experiment provide a clear direction to optimize the pulsed laser system in the future.

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