近年來976 nm全光纖雷射模組因可應用在通訊、感測、材料加工及作為泵浦源而備受重視。然而在單體式全光纖結構中實現高功率、高效率的 976 nm脈衝輸出，仍面臨數項挑戰。首先摻鐿增益介質在約 1030 nm 附近具較強的增益競爭，使 976 nm 操作受限1030 nm波段的自發放大輻射 (Amplified Spontaneous Emission, ASE) 競爭。其次，為了降低非目標波段增益並維持緊湊腔體而採用短增益光纖，在高功率泵浦下可能造成泵浦吸收不足。為了克服挑戰，本論文提出了一套創新、緊湊且低成本的同質摻鐿雙共振腔全光纖式雷射架構系統，並探討了被動 Q開關 (Passively Q-switched) 與增益開關 (Gain-switched) 的雷射動態機制。
本研究首先利用氫氟酸蝕刻技術減小增益光纖的批覆層直徑，從而提高披覆層與纖芯面積比(core-to-clad area ratio, CCAR)數值，目的用來提升使用短增益光纖架構系統的泵浦效率。首先透過Rsoft BeamPro，以光束傳播方法(beam propagation method, BPM)對光束傳輸進行數值模擬；並於實驗中驗證使用經 HF 蝕刻的摻鐿光纖，其長度僅有 18 cm，在輸出最大976 nm之雷射功率 10.3 W下，其轉換效率為 25.4%的緊湊型雷射系統，且未對 1030 nm 的發射進行任何抑制。
　在此基礎上，進一步設計同質摻鐿雙共振腔全光纖式雷射架構系統，並修正了一組雷射速率方程模型，用來模擬調Q開關與增益開關之自平衡切換系統，並考慮單模至多模共振腔中的損耗、模場直徑(Mode-Field Diameter, MFD)、模場不匹配(Mode-Field-Area Mismatch, MFAM)，以及殘餘泵浦進入SAQS fiber對系統性能的影響。最後設計並完成一被動 Q 開關的摻鐿全光纖式雙共振腔雷射，其工作波長為 976 nm，達 4.3 W 的平均輸出功率並具 16.4% 轉換效率。其輸出脈衝特性包括：150 ns 脈寬、383 kHz 重複率、11.3 μJ 的脈衝能量，以及 75 W 的峰值功率。研究數值模擬與實驗結果交互驗證，透過優化蝕刻技術可改良光纖表面粗糙度品質，更高 CCAR數值可提升被動調Q開關雷射架構的整體轉換效率，理論模型亦替未來高穩定且高重複率的976 nm脈衝輸出系統架構奠定理論基礎與實作工程範例。

In recent years, 976-nm all-fiber laser modules have garnered considerable attention for telecommunications, sensing, materials processing, and pump source applications. However, achieving high-power, high-efficiency 976-nm pulsed emission in a monolithic all-fiber structure is hindered by strong 1030-nm amplified spontaneous emission (ASE) competition and insufficient pump absorption when using short gain fibers to maintain a compact cavity. To overcome these challenges, this thesis proposes a compact, cost-effective monolithic ytterbium-doped dual-cavity all-fiber laser and investigates its passively Q-switched and gain-switched dynamics.

This study first utilized hydrogen fluoride (HF) etching to reduce the gain fiber's cladding diameter, increasing the core-to-clad area ratio (CCAR) to enhance pump efficiency in short-gain-fiber systems. Beam transmission was numerically simulated using the beam propagation method (BPM). Experimentally, using an 18-cm HF-etched ytterbium-doped fiber, the compact laser delivered a maximum 976-nm power of 10.3 W with a 25.4% conversion efficiency, without requiring additional 1030-nm suppression measures. Building upon this foundation, a monolithic ytterbium-doped dual-cavity all-fiber laser system was further designed, and a set of coupled rate equations was modified to model the self-balanced system of the Q-switched and gain-switched mechanisms. The model accounted for the losses incurred when transitioning from single-mode to multimode resonators, mode-field diameter (MFD) variations, mode-field-area mismatch (MFAM), and the impact of the residual pump entering the saturable absorber Q-switch (SAQS) fiber. Ultimately, a passively Q-switched 976-nm dual-cavity laser was realized, achieving 4.3 W average power with a 16.4% conversion efficiency. The output featured a 150-ns pulse width, a 383-kHz repetition rate, an 11.3-μJ pulse energy, and a 75-W peak power.

Cross-validation of simulations and experiments confirmed that optimizing the etching improves surface roughness, and a higher CCAR enhances the overall conversion efficiency. The theoretical model establishes a solid foundation and a practical engineering paradigm for future highly stable, high-repetition-rate 976-nm pulsed systems.

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