中文摘要

對於1300至1600 nm光通訊波段，Cr4+離子成為最佳活性離子之選擇，且已被用於掺雜於各種主材而開發出許多種雷射，包含Cr4+:forsterite、Cr4+:Y2SiO5與Cr4+:YAG (yttrium aluminum garnet)，其中由於YAG本身熱、光優越的特性，使之成為最佳雷射主材之一，但將Cr4+:YAG抽成光纖後，其材料特性及微結構之了解仍極為有限。

本論文利用LHPG (laser-heated pedestal growth)法來生長高品質的Cr4+:YAG晶體光纖。藉由此系統之容易更換生長參數的特性，我們可以成功地生長出不同生長速度與不同纖心直徑之Cr4+:YAG晶體光纖。並以fused-silica玻璃包覆Cr4+:YAG共同生長技術，可得到具有內(YAG+SiO2)、外(SiO2)層纖衣波導結構之Cr4+:YAG晶體光纖，其纖心直徑最小為11 mm，故有關Cr4+:YAG晶體光纖之製程與雷射元件之機械製備和其光學鍍膜設計等在本文中將作詳細說明。

然而為了更了解此種晶體光纖之顯微結構及其於不同生長參數下的變化，本論文亦將藉由高解析穿透式電子顯微鏡(high-resolution transmission electron microscopy；HRTEM)來觀察單、雙層纖衣結構之Cr4+:YAG晶體光纖，其中HRTEM影像提供於內、外層纖衣介面與纖心之奈米尺度微結構資訊，並進一步分析Cr4+:YAG晶體光纖於生長時之擴散過程與不同生長速度對擴散過程之關係。此外，本文亦藉由EPMA(electron-probe micro-analyzer)與EDX(energy dispersive X-ray spectrometer)量測來了解單、雙層纖衣結構晶體光纖中之CaO與Cr2O3掺雜濃度分佈，並配合Cr4+螢光強度量測來研究其與微結構及掺雜濃度之關係。

ABSTRACT

For the generation of broadband tunability over 1300 nm to 1600 nm range in optical communications, Cr4+ ions have been demonstrated in a number of hosts including Cr4+:forsterite, Cr4+:Y2SiO5, and Cr4+:YAG. Since YAG is a cubic crystal with Ia-3d space group, its excellent thermal and optical properties has drawn extensive studies. In recent years, various modes of operation using Cr4+:YAG as laser gain medium have been achieved since the first tunable CW laser of Cr4+:YAG bulk gain medium was demonstrated by Shestakov, et al in 1988.

Experimentally, the Cr4+:YAG crystal fiber was grown by the laser-heated pedestal growth (LHPG) method which provides outstanding crystal quality and can easily change growth conditions, such as growth speed and core diameter. A double cladding technique was developed with pure YAG, silica/YAG mixture, and pure silica as the core, inner cladding, and outer cladding, respectively. The smallest core diameter we achieved is 11 mm. In this thesis, the fabrication process of the Cr4+:YAG crystal fiber laser involving crystal fiber growth, sample preparation, and coating design will be presented in detail.

In order to understand the relation between the microstructure of Cr4+:YAG crystal fibers and the growth conditions, high-resolution transmission electron microscopy (HRTEM) was employed, which reveals the nano-scale information in the core region, the inner-outer cladding interface, and the mechanism of inter-diffusion process during growth. In addition, the thesis also describes the specimen preparation procedures of crystal fibers for the HRTEM analysis. Furthermore, quantitative analysis of Cr4+:YAG crystal fiber was employed by electron-probe micro-analyzer (EPMA) and energy dispersive X-ray spectrometer (EDX), showing accurate characterization of the constitute elements and concentrations. The comparison of Cr4+ fluorescence and dopant concentration of CaO and Cr2O3 will also be presented in this thesis.

目錄

中文摘要 i
英文摘要 ii
目錄 iii
圖目錄 v
表目錄 ix

第一章 晶體光纖簡介 1
1.1 可調波長之固態雷射 1
1.2 Cr4+:YAG雷射歷史回顧 4
1.3 晶體光纖之應用 7
1.4 論文簡介 9
第二章 Cr4+:YAG晶體光纖特性 11
2.1 YAG晶體結構 11
2.2 電荷補償 14
2.3 能階模型 16
2.4 晶纖中之傳輸 19
2.5 結論 22
第三章 Cr4+:YAG晶體光纖雷射元件製作 23
3.1 雷射加熱提拉生長法 23
3.2 Cr4+:YAG晶體光纖之生長 28
3.3 元件之機械製備 30
3.3.1 銅鋁及錫鉛合金包覆 30
3.3.2 研磨、拋光 34
3.4 結論 38
第四章 Cr4+:YAG晶體光纖雷射 39
4.1 雷射共振腔架構 39
4.2 光學鍍膜 41
4.3 雷射架構 45
4.4 總結 49
第五章 Cr4+:YAG晶體光纖之微結構分析 51
5.1 TEM基本原理 51
5.1.1 TEM構造 51
5.1.2 電子源與電子槍 52
5.1.3 TEM成像系統 56
5.2 EDX基本原理 58
5.2.1 EDX簡介 58
5.2.2 半導體偵測器 60
5.2.3 定性與定量分析 61
5.3 Cr4+:YAG晶體光纖之TEM試片製作 64
5.3.1 鑲埋 64
5.3.2 機械減薄 64
5.3.3 離子束減薄 66
5.4 高解析TEM分析結果 71
5.4.1 單層纖衣與雙層纖衣之微結構分析 72
5.4.2 Cr4+:YAG晶體光纖之化學組成 77
5.4.3 雙層纖衣結構之相互擴散機制 83
5.4.4 纖心與內層纖衣結晶顆粒之分析 86
5.4.5 雙層纖衣於不同生長速度之微結構比較 95
5.5 總結 104
第六章 結論 105

參考文獻 108
中英對照表 114

參考文獻

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第三章 Cr4+:YAG晶體光纖雷射元件製作
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