摻鉻釔鋁石榴石晶體(Cr4+:YAG)為一引人注目的增益介質，主要是因其自發輻射頻譜半高寬，為從1253 奈米至1530 奈米，涵蓋了大部份的光通訊低損耗波段。如此寬頻的光譜特性，使其適合發展為光通訊用之自發輻射放大光源、光放大器、和可調波長雷射。而將晶體生長成光纖的形態具有比塊材更佳的光波導效果，同時產生更高的光增益。對於雷射的應用，因晶體光纖可承受較大之光強度且散熱較佳，可發展低損耗閥值和高效率之雷射輸出。

我們得到室溫下最低的雷射閾值功率為0.75 mW，低於任何文獻記述掺鉻雷射之閥值(threshold)功率五百倍以上，且斜率效率達到6.9%。能夠產生超低閥值功率是由於低傳輸損耗(0.08 dB/cm)以及纖心有較高的激發光源強度所致，如此超低閥值的工作條件使得雙纖衣晶體光纖雷射能夠與目前的光通訊系統相容，同時我們也針對所研製之晶體光纖雷射進行模擬與實驗結果做比對。

此外以穩態塊材模型，配合Lagrange Multiplier 方法求解最佳化，不但與塊材或晶纖型式之實驗數據相當符合之外，並進一步預測在室溫下可獲得相當低的閥值及高斜率效率。吾人相信摻鉻釔鋁石榴石晶體可發展成為光纖通訊的一種體積小、低耗材之寬頻可調的雷射元件。

Cr4+:YAG is an attractive gain medium due to its broad 3-dB emission spectrum ranging from 1253 to 1530 nm, which cover the low-loss window of the silica fiber. Such a broadband haracteristic offers a potential to develop a broadband amplified spontaneous emission (ASE) light source, optical amplifier, and tunable laser. Growing the Cr4+:YAG bulk crystal into fiber form is necessary for generating larger gain by the better optical confinement of the waveguide structure. For the application of laser, it is superior to bulk crystals for reducing lasing threshold and obtain the high slope efficiency due to the beter optical confinement and heat dissipation.

A record-low threshold of 0.75 mW was achieved at room temperature. It is more than 500 times lower than any previously reported Cr4+:YAG lasers, and a slope efficiency of 6.9% was obtained. The ultralow-threshold lasing is made possible by the low propagation loss of 0.08 dB/cm and the high pump intensity of the core. Such a low-threshold operation makes the double-clad crystal fiber laser be compatible to present optical communication systems.

Furthermore, we demonstrate that the proposed optimization algorithm can provide an efficient and direct approach to analyzing both fiber structure and bulk medium in terms of practical application requirements. The simulation results reveal that Cr4+:YAG DCF lasers offer advantages over bulk lasers in terms of low-threshold lasing and high efficiency, which are essential for their use in optical communication systems.

中文摘要 Ⅰ
英文摘要 Ⅱ
致謝 Ⅲ
目錄 Ⅳ
圖目錄 Ⅵ
表目錄 Ⅷ
第一章 簡介 1
第二章 Cr4+:YAG 晶體光纖雷射原理 4
2.1 晶體特性 4
2.2 能階模型 13
2.3 傳輸模態 17
第三章 鉻離子濃度分析 21
3.1 纖心組成及螢光量測 21
3.2 三價及四價鉻離子之螢光分析 23
3.3 氮及氧環境下對鉻離子退火之影響 25
第四章 Cr4+:YAG 雙纖衣晶體光纖雷射 30
4.1雷射共振腔架構 30
4.2 雷射共振腔之光學鍍膜 33
4.3 Cr4+:YAG 雙纖衣晶體光纖雷射之耦光 37
v
4.4 雷射系統架構 39
4.5 Cr4+:YAG實驗結果分析 40
第五章 Cr4+:YAG 雷射最佳化 44
5.1最佳化之解析解 44
5.2 不同晶纖參數之分析 48
5.3 結果及討論 50
第六章 結論 58
參考文獻 60
中英對照表 64
自傳 68
論文表列 69

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