本文提出兩種適用於980nm高功率雷射與單模光纖耦光之新結構橢圓光纖微透鏡。其中四角錐形光纖微透鏡(Quadrangular-Pyramid-Shaped Fiber Microlens；QPSFM)的製作係將光纖研磨形成四角錐形，然後經過光纖熔接機熔燒而形成橢圓微透鏡端面。與傳統的楔形光纖微透鏡相比，QPSFM製程能控制光纖微透鏡在兩個軸向的曲率半徑(Radius of Curvature)，進而控制光纖遠場長寬比(Aspect Ratio)，使其與雷射橢圓的遠場匹配。經實驗證實QPSFM有高達83%的最大耦光效率。另一結構為錐式楔形光纖微透鏡(Conical-Wedge-Shaped Fiber Microlens；CWSFM)，其製作係先將光纖研磨成圓錐形，然後再對圓錐形光纖作楔形研磨而形成錐式楔形，最後經過熔燒而形成優良的橢圓微透鏡端面。實驗證實CWSFM有高達84%的最大耦光效率。

QPSFM製作需要五次研磨，研磨偏軸量(Offset)的範圍在0.5~3.0μm之間，平均研磨偏軸量為1.5μm。由於研磨偏軸量較大，因此QPSFM的製程良率偏低。CWSFM製作只需要三次研磨，且研磨量較少，研磨偏軸量的範圍在0.3~1.5μm之間，平均研磨偏軸量為0.8μm。由於CWSFM的研磨偏軸量比QPSFM小，故CWSFM的製程良率較高。在耦光效率大於70%的條件下，CWSFM的製程良率達六成，而在耦光效率大於60%的條件下，CWSFM的製程良率更高達九成六。

我們在此建構了一個以繞射理論為主的雷射與光纖耦光數學模型，根據這個模型，可以計算出耦光效率、光纖對準容忍度和光纖透鏡偏軸量容忍度，理論計算結果與實驗結果相當一致。本文提出的兩種新結構光纖微透鏡皆被證實有極高的耦光效率，其中CWSFM更同時具有製程簡單與良率高的優點，有適用於商用高功率幫浦雷射模組的潛力。

Two new schemes of fiber microlenses for coupling between the high-power 980nm laser diodes and single-mode fibers (SMFs) are proposed. The quadrangular-pyramid-shaped fiber microlens (QPSFM) is fabricated by grinding a quadrangular-pyramid-shaped endface and then through heating in a fusing splicer to form an elliptical microlens endface. In comparison to the traditional wedge-shaped fiber microlens, the QPSFM structure can control two axial curvatures to form an elliptical microlens endface, and then control the aspect ratio of fiber far-field pattern to match the elliptical mode fields of lasers. The coupling efficiency of 83% for the QPSFM has been demonstrated. Another scheme of fiber microlens is the conical-wedge-shaped fiber microlens (CWSFM). The CWSFM is fabricated by grinding a conical-shaped fiber endface, then grinding a pair of wedge planes on the conical-shaped fiber endface, and finally through heating in a fusing splicer to form a good elliptical microlens endface. The coupling efficiency of 84% for CWSFM has been demonstrated.

The fabrication of QPSFM requires five-step grinding processes. The range of grinding offset is 0.5~3.0μm, and the average of grinding offset is 1.5μm. The fabrication yield of QPSFM is low due to the large grinding offset. The fabrication of CWSFM requires only three-step grinding processes. The range of grinding offset is 0.3~1.5μm, the average of grinding offset is 0.8μm. The fabrication yield of CWSFM is high due to the small grinding offset. The fabrication yield is about 60% for 70% coupling efficiency; whereas the fabrication yield becomes 96% for 60% coupling efficiency.

The laser-to-SMFs coupling of the fiber microlens was modeled based on the diffraction theory. The coupling efficiency, the tolerance of alignment, and the tolerance of fiber microlens offset were calculated according to this model. There is a good agreement between the simulation and the experiment values. In this study, two new scheme of fiber microlenses of the QPSFM and CWSFM with high coupling efficiency have been demonstrated. The CWSFM structure has the benefits of simple process and high yield that is suitable for use in commercial high power laser module.

內容目錄
頁次
中文摘要 Ⅰ
英文摘要 Ⅱ
誌謝 Ⅲ
內容目錄 IV
表目錄 VIII
圖目錄 IX

第一章 緒論
1-1 前言 1
1-2 研究動機 2
1-3 文獻回顧 3
1-4 章節簡介 8

第二章 理論分析
2-1 光纖透鏡設計概念 18
2-2 雷射波前變化的計算 19
2-3 理論模型 20
2-3-1 耦光理論模型 20
2-3-2 光纖對準容忍度的計算 26
2-3-3 偏軸量對耦光損失的計算 27
2-4 光纖透鏡發散角的計算 29

第三章 實驗測量技術
3-1 980nm雷射特性介紹 43
3-2 雷射特性測量 44
3-2-1 雷射之功率-電流曲線測量 44
3-2-2 雷射發散角與長寬比的測量 45
3-2-3 雷射頻譜的測量 46
3-3 透鏡結構參數測量 46
3-4 耦光效率測量 47
3-5 耦光效率校正 47
3-6 光纖遠場圖樣測量 47

第四章 四角錐形光纖透鏡
4-1 前言 56
4-2 製程 57
4-2-1 四角錐形光纖研磨 57
4-2-2 研磨去尖點 60
4-2-3 光纖熔燒 60
4-3 實驗結果 62
4-3-1 耦光效率 62
4-3-2 對準容忍度分析 63
4-3-3 光纖遠場圖樣 64

第五章 錐式楔形光纖透鏡
5-1 前言 73
5-2 製程 73
5-2-1錐式楔形光纖研磨 73
5-2-2 蝕刻去尖點 75
5-2-3光纖熔燒 76
5-3 實驗結果 77
5-3-1 耦光效率 77
5-3-2 對準容忍度分析 78
5-3-3 光纖遠場圖樣 79
5-3-4 良率分析 79

第六章 結論與討論
6-1 結論 89
6-2 未來工作 93
參考資料 96
附錄A 雷射與光纖元件資料 100
附錄B 耦光模擬程式 112
作者著作 117
作者簡介 118


表目錄
頁次
表1.1 各種適用於通訊波段雷射的光纖微透鏡特性比較 4
表1.2 各種適用於980nm雷射的光纖微透鏡特性比較 6
表2.1 不同形式光纖微透鏡的耦光模擬結果 25
表2.2 不同雷射長寬比下的最佳橢圓形光纖微透鏡參數 25
表2.3 橢圓形光纖微透鏡的3dB容忍度模擬值 27
表4.1 非對稱結構與其橫截面形狀 57
表4.2 四角錐形光纖微透鏡的最佳參數 62
表4.3 四角錐形光纖微透鏡的3dB容忍度模擬值 63
表5.1 錐式楔形光纖微透鏡的最佳參數 78
表5.2 錐式楔形光纖微透鏡的3dB容忍度模擬值 78
表5.3 錐式楔形光纖微透鏡25個樣本的耦光效率 80
表6.1 QPSFM與CWSFM的比較 90



圖目錄
頁次
圖1.1 掺鉺光纖放大器的架構與能階圖 9
圖1.2 雷射與光纖模態的不匹配 10
圖1.3 熔融拉伸光纖微透鏡 11
圖1.4 燈泡狀接合式光纖微透鏡製程示意圖 11
圖1.5 燈泡狀接合式光纖微透鏡 12
圖1.6 典型單模光纖折射率分佈圖 12
圖1.7 微錐狀光纖微透鏡 13
圖1.8 UV膠點膠光纖微透鏡製程示意圖 13
圖1.9 UV膠點膠光纖微透鏡 14
圖1.10 圓錐形光纖蝕刻裝置示意圖 14
圖1.11 雙曲線形光纖微透鏡 15
圖1.12 外徑漸擴的楔形光纖微透鏡 15
圖1.13 楔形接合光纖微透鏡 16
圖1.14 非對稱雙曲線形光纖微透鏡 16
圖1.15 雙楔形光纖微透鏡 17
圖2.1 典型980nm雷射模場變化 31
圖2.2 雷射波前曲率經過橢圓形微透鏡後的變化 32
圖2.3 雷射與單模光纖的二維耦光模型 33
圖2.4 楔形光纖微透鏡二維示意圖 34
圖2.5 雙楔形光纖微透鏡二維示意圖 34
圖2.6 圓柱光纖微透鏡二維示意圖 34
圖2.7 橢圓光纖微透鏡二維示意圖 35
圖2.8 雙曲線光纖微透鏡二維示意圖 35
圖2.9 橢圓光纖微透鏡對不同長寬比雷射的耦光模擬結果 36
圖2.10 光纖微透鏡與雷射未對準示意圖 37
圖2.11 移動未對準對耦光影響的計算結果 38
圖2.12 轉動未對準對耦光影響的計算結果 39
圖2.13 偏軸量對耦光影響的計算結果 40
圖2.14 光纖微透鏡曲率半徑與發散角的關係 41
圖2.15 光纖微透鏡發散角對耦光影響的計算結果 42
圖3.1 GRIN-SCH應變量子井雷射結構與能帶圖 50
圖3.2 遠場橢圓長寬比的定義 50
圖3.3 工研院雷射功率-電流曲線測量結果 51
圖3.4 工研院雷射遠場測量結果 52
圖3.5 工研院雷射頻譜測量結果 53
圖3.6 微透鏡曲率半徑與軸心偏移示意圖 53
圖3.7 雷射與光纖耦光效率量測之裝置示意圖 54
圖3.8 發散角計算示意圖 54
圖3.9 遠場圖樣測量結果 55
圖4.1 實驗用單模光纖折射率分佈圖 65
圖4.2 楔形光纖熔燒凹陷現象 65
圖4.3光纖研磨系統 66
圖4.4 四角錐形光纖 67
圖4.5 光纖微透鏡熔燒凸起過程示意圖 68
圖4.6 去尖點四角錐形光纖的菱形橫截面示意圖 68
圖4.7 四角錐形光纖微透鏡 69
圖4.8 曲率半徑Rlx、Rly和結構角度α、β的關係示意圖 70
圖4.9 耦光效率對垂直曲率半徑的關係圖(一) 71
圖4.10 耦光效率對垂直曲率半徑的關係圖(二) 71
圖4.11 四角錐形光纖微透鏡的遠場圖樣測量結果 72
圖5.1 錐式楔形光纖微透鏡的製程示意圖 81
圖5.2 錐式楔形光纖 82
圖5.3 蝕刻去尖點的裝置示意圖 83
圖5.4 蝕刻造成的凹陷現象 83
圖5.5光纖纖核熔燒凸起現象 84
圖5.6 錐式楔形光纖微透鏡 85
圖5.7 耦光效率對垂直曲率半徑的關係圖 86
圖5.8 錐式楔型光纖微透鏡的遠場圖樣測量結果 87
圖5.9 測量樣本的耦光效率直方圖 88
圖6.1 橢圓錐形光纖研磨原理 94
圖6.2 橢圓錐形光纖結構 95
圖6.3 動態光纖蝕刻製程示意圖 95

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