本論文之主要研究目標為改善被動式Q開關脈衝雷射架構中製作的模態場適配器，因光子密度驟增而產生斷裂的問題，以及降低因模態場不匹配所產生的損耗，進而提升被動式Q開關1030-nm全光纖雷射之效率及輸出脈衝特性。架構採用多模雷射二極體來做為泵浦光源，並使用雙披覆層光纖來組成披覆層泵浦系統，以達到高功率輸出雷射。系統中的增益介質與可飽和吸收體皆為摻鐿光纖，且設置第二共振腔的增益開關機制與模態場面積不匹配技術來增加Q開關的切換速度。於架構中採用新的漸進式pump power stripper，有效的去除披覆層的泵浦能量，這能避免披覆層產生多模干擾，影響最後輸出的脈衝品質。共振腔內因光纖之間模態場不匹配所造成的損耗，將透過熱擴張纖核法以及將光纖負載氫氣來改善。因應不同的模態場直徑差距，而設計不同的TEC實驗，成功達成各個熔接點穿透率皆能突破95 %，即各個熔接點的穿透損耗皆為0.22 dB以內。經過最佳化實驗參數之後，整個共振腔內初始損耗最大的熔接點，其穿透率從38.64 %大幅提升至97.45 %，即穿透損耗可從4.13 dB大幅降至0.11 dB。

The main purpose of study is to improve the mode-field adaptor in the passive Q-switched laser, the problem of cracking due to the sudden increase of photon density, and the expectation of reducing the loss due to modal field area mismatch. Therefore, the efficiency and output pulse characteristics of the passive Q-switch 1030 nm all-fiber laser can be improved. The architecture uses a multi-mode laser diode as the pumping source and uses a double-cladding fiber to form a cladding pumping system to achieve high power output lasers. The gain medium and the saturable absorber in the system are both ytterbium-doped fibers, and the switching speed of the Q switch is increased by the gain switching mechanism of setting the second laser resonator and the modal field area mismatching technique. The new progressive pump power stripper is used in the architecture to remove the pumping energy of the cladding layer effectively and avoid multi-mode interference in the cladding layer to affect the pulse quality of the final output. The loss in the laser resonator due to the modal fields mismatch between fibers will be improved by the thermal expanded core method and the loading of the fiber with hydrogen. We designed different TEC experiments according to different modal field diameter differences to achieve 95% of each fusion point, that is, the transmission loss of each fusion point is within 0.22 dB. After optimizing the experimental parameters, the initial transmission of the maximum in the laser resonator is increased from 38.64% to 97.45%, that is, the transmission loss can be reduced from 4.13 dB to 0.11 dB.

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