此論文是利用cladding pump的全光纖系統下，以915-nm之半導體多模雷射源作為泵浦光源來激發摻鐿光纖，產生976-nm雷射。但未經過蝕刻之摻鐿光纖無法產生976-nm之雷射，故我們利用氫氟酸配合步進馬達來蝕刻縮減摻鐿光纖直徑，提升泵浦光源的強度，進而降低雷射門檻，增加雷射效率。蝕刻後光纖損耗原因主要發生在taper region的品質，我們發現用24.5%之HF所量測之穿透率高於30% HF，原因是因為30%之HF所製作之taper region的斜率較大，使光會直射出光纖，而他的taper length也比較短，taper length越短越不利穿透率。而蝕刻後之摻鐿光纖寬度越大，976-nm之雷射增益越小，反之。故我們希望將長度14公分的摻鐿光纖直徑蝕刻至40 μm以下，並且穿透率達75%以上。我們也利用熱擴張纖核的技術來製作模態場接合器，解決共振腔中因為模態場不匹配所造成的損耗，將損耗降至最低。另外我們也分析在摻鐿光纖之前、之後、同時製作MFA對雷射輸出所造成之影響，發現同時製作MFA所得到之最高雷射輸出功率為283 mW，雷射門檻也由3.6W降低至2.8 W。

This thesis studies on the 915-nm Laser Diode pumped Yb-doped fiber to generate 976-nm laser which is under the double cladding pumping of the all-fiber system. Because the Yb-doped fiber is difficult to laser at 976-nm,we decreased the diameter of the Yb-doped fiber to increase the intensity of pump source. Furthermore, the higher intensity of pump source, the lower laser threshold we have. We used the step motor to etch the Yb-doped fiber and the etching solution is HF(24.5%). After several experiments, we can calculate the etching rate is 0.9 μm/minute. When we etched 100 minutes, the diameter of fiber was 36 μm and the transmission was 77.5%. The transmission loss is due to the quality of the tapering region. If the surface of taper region becomes smoother, the transmission will be higher. We also find the smaller diameter of the Yb-doped fiber, the higher gain we have in 976-nm laser. In addition, we utilized thermal expanded core technique (TEC) to make the mode-field adaptor (MFA) solve the problems of the loss due to mold-field mismatch, and reduce the loss at the resonator. We also analysed the situation that we manufacture the MFA before the Yb-doped fiber, after the Yb-doped fiber and the both side of the Yb-doped fiber. After analysing the situation, we found that when we manufacture the MFA on the both side of the Yb-doped fiber, we can measure the max output power and reduce the threshold. Finally, the highest output power we measured is 283 mW and the laser threshold is 2.8 W.

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