臺灣博碩士論文加值系統

本篇論文採用的系統為全光纖架構，使用波長915-nm的LD(Laser Diode)，將雷射注入 DCF(double-cladding fiber)光纖進行 cladding pump，激發摻雜鐿的光纖產生波長976-nm的 CW雷射，由於先前實驗的經驗，攙鐿光纖如果長度太長，會有模態競爭的問題，而先產生了1030-nm的四階雷射，再加上因為採用cladding pump的方式，使得915-nm的雷射讓core摻雜的光纖吸收效率降低。因此本篇論文的目的為使用氫氟酸溶液蝕刻摻鐿光纖，使其直徑縮減，提升摻雜粒子對於光源(915-nm LD)的吸收效率。

我們使用Z825B馬達驅動平台下降來蝕刻光纖，Power Stripper過濾數值孔徑(NA)高的光以提升穿透率，pump光源的能量在蝕刻後的光纖傳遞，傳遞到taper region內60微米以下時，損耗會開始增加，因此使用變速度兩段式的蝕刻，將60微米以下的taper region斜率製作更緩和，使得穿透率從原先的54%提升到71.2%，使用摻鐿光纖蝕刻後，雷射效率也由去年的18.66%提升至22.4%證實過濾掉高階模態的光線對於提升雷射效率有幫助。
我們還會使用Rsoft軟體模擬光源在Tapered Fiber中的損耗是否與Taper長度有關係，以此來設計摻鐿光纖共振腔的Taper Length，我們發現即使Taper Length縮短到2mm也不會有損耗，由於馬達下降的速度有極限因此我們將Taper Length由兩段式變速蝕刻的21.76mm縮短至單一速度蝕刻的7.07mm，雷射效率雖然僅有17%，但是產生雷射的threshold 也由從前的2.2W降至1.6W。

This thesis uses all-fiber laser system with cladding pump technique.In order to generate 976-nm CW laser, we use 915-nm multimode laser diode as a pumping source to pump Ytterbium doped fibers. Considering mode competition from former experiences, if longer Yb-doped fiber adopted, it will generate 1030-nm laser first which is not expected. Besides, adopting cladding pump system causes low efficiency for the core to absorb pumping source, which leads to lower pump efficiency of doped fibers. Therefore, our main purpose is to increase pump intensity by reducing cladding diameter. That is, we etched Yb-doped fiber with 24.5% Hydrofluoric acid in order to improve its performance of lasering. Before etching Yb-doped fiber, we did transmission test to get familiar with etching process by using Z825B motor. Also, we reformed the whole laser system by replacing old 915-nm LD, adding power stripper to annihilate high-order beam from new 915-nm LD. Meanwhile, we did stimulation by using Rsoft to find the relationship between taper length and transmission. We found out that even with 2mm of taper region, the transmission of the beam with NA=0.24 is near 100%. Because the loss of light propagating becomes larger when the cladding diameter is lower than 60μm, we set the Z825B motor to various speed to do 2 step etching. By 2 step etching, we kept the transmission up to 71.2%. Thus the parameter set of this etching process will be adopted to use on the etching of Yb-doped fiber. Eventually, with the help of the power stripper and 2 step etching, the threshold of generating 976-nm laser decreased from 2.1W down to 1.6W. Laser efficiency increased from 18.66% up to 22.4%.

摘要 I
致謝 i
目錄 - 1 -
圖目錄 - 3 -
表目錄 - 5 -
符號表 - 6 -
第一章 緒論 - 7 -
1-1 前言 - 7 -
1-2 研究動機 - 8 -
第二章 原理 - 11 -
2-1雷射原理 - 11 -
2-2 976-nm摻鐿光纖CW雷射架構設計 - 12 -
2-3 摻鐿光纖中的模態競爭 - 15 -
2-4 雷射模擬推導 - 17 -
第三章 SMF-130V蝕刻與穿透率實驗 - 25 -
3-1 實驗設計 - 25 -
3-2 蝕刻實驗與測量 - 29 -
3-2-1 Z825B馬達設定 - 29 -
3-2-2 蝕刻 - 31 -
3-2-3 測量與結果 - 33 -
3-3 實驗架構改善 - 35 -
3-3-1 更換輸入源以及加入Power Stripper - 35 -
3-3-2 架構改善後測量 - 39 -
3-3-3 架構改善後的蝕刻與量測 - 40 -
3-3-4 兩段式變速蝕刻及穿透率測量 - 43 -
3-4 Rsoft 模擬 - 46 -
3-4-1數值孔徑NA及與光纖直徑的關係 - 46 -
3-4-2 Rsoft簡介 - 48 -
3-4-3 Rsoft模擬與結果 - 50 -
3-5 結論 - 56 -
第四章 摻鐿光纖蝕刻與測量 - 57 -
4-1 摻鐿光纖實驗 - 57 -
4-1-1 摻鐿光纖蝕刻 - 57 -
4-1-2 摻鐿光纖雷射測量 - 59 -
4-2 雷射結果 - 60 -
4-3 雷射效率改善與討論 - 63 -
4-4 結論 - 66 -
第五章 總結 - 68 -
5-1 成果與討論 - 68 -
5-2 未來展望 - 69 -
參考文獻 - 71 -

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