由於近年來光通訊頻寬需求急速增加，使得研製具有超寬頻特性之增益介質成為一重要課題。其中，以摻鉻釔鋁石榴石(Cr4+:YAG)於光通訊波段具有3 dB頻寬高達265 nm之超寬頻特性最受矚目。本實驗室已成功以雷射加熱基座生長法(laser-heated pedestal growth method)研製出具有波導結構、低損耗及超低激發閥值(ultralow threshold)之摻鉻釔鋁石榴石雙纖衣晶體光纖(Cr4+:YAG double-clad crystal fiber)超寬頻光源、光放大器及雷射，顯示摻鉻釔鋁石榴石雙纖衣晶體光纖在未來光通訊中極具有潛力取代目前之摻鉺光纖。故本論文著重於研究奈米尺度光學與微結構之相互關係，進而提升摻鉻釔鋁石榴石雙纖衣晶體光纖所研製之元件效率。

在奈米尺度光學與微結構方面，近場掃描式光學顯微鏡( near-field scanning optical microscopy)和高解析穿透式電子顯微鏡(high-resolution transmission electron microscopy)等兩種技術在奈米光譜學與奈米結構上扮演了很重要的角色。本論文首先針對具有異質結構(heterostructure)、高硬度及極脆弱之摻鉻釔鋁石榴石雙纖衣晶體光纖，成功製作高解析穿透式電子顯微鏡之試片，並藉此試片首度以具有高空間分辨率(spatially resolved)之近場掃描式光學顯微鏡解析出位於內層纖衣(inner cladding)內奈米結晶顆粒之近場螢光頻譜特性，並搭配高解析穿透式電子顯微鏡於微結構上作一比較。此外，本論文亦藉由量測摻鉻釔鋁石榴石雙纖衣晶體光纖纖心(core)之近場光譜特性，分析因纖心與內層纖衣之熱膨脹係數不同所產生之應力變化(strain)分佈、螢光生命週期及生長參數三者關係。對應11 μm和25 μm纖心，應變量分別為-0.04 %和0.06 %，預測應變量為0 %時，纖心直徑約為20 μm。

With the escalating demands for optical communication network system, the need for broadband gain medium in optical communication has increased. Among them, Cr4+:YAG crystal has shown an exceptionally successful broadband amplified spontaneous emission (ASE) light source that fully cover 1.2-1.6 μm range (3-dB bandwidth up to 265 nm). More recently, we demonstrated the realization of a waveguiding, low-loss, and ultralow threshold Cr4+:YAG double-clad crystal fiber (DCF) based ultrabroadband ASE light source, optical amplifier, and laser grown by the codrawing laser-heated pedestal growth (LHPG) technique. These results demonstrate the potential of the Cr4+:YAG DCF for the replacement of the erbium doped fiber in future optical communications. In this thesis, we focus on the correlation between the nanospectroscopy and nanostructure of the Cr:YAG DCF in order to further improve its device performance.

For nanospectroscopic and nanostructural characterizations, near-field scanning optical microscopy (NSOM) and high-resolution transmission electron microscopy (HRTEM) techniques have played key roles. In this thesis, we successfully prepared the HRTEM specimen of Cr:YAG DCF, which is heterostructure, ultrahard, but fragile. Here we show the first study on the nanospectroscopy and nanostructure of the nanocrystals in the inner cladding of Cr:YAG DCF by highly spatial resolved NSOM. The NSOM results were compared with those obtained by HRTEM. In addition, the difference in thermal expansion coefficients between a YAG core and an inner cladding creates a significant localized strain field beneath the core, which can result in optical confinement and provide the possibility to simultaneously control the Cr3+ and Cr4+ fluorescence with systematically varied growth parameters. This new class of strain-tunable Cr:YAG DCF opens up new opportunity to improve the performance of the Cr:YAG DCF based ultrabroadband light source, optical amplifier, and crystal fiber laser in all-optic fiber communications.

目錄
中文摘要 i
英文摘要 ii
致謝 iii
目錄 iv
圖目錄 vi
表目錄 xi
第一章 緒論 1
第二章 Cr:YAG雙纖衣晶體光纖之特性 4
2.1 Cr:YAG晶體之結構與特性 4
2.2 Cr:YAG能階模型及光譜特性 10
2.2.1 Cr3+:YAG能階、吸收及放射光譜 10
2.2.2 Cr4+:YAG能階、吸收及放射光譜 14
2.3雙纖衣晶體光纖之傳輸特性 18
2.4應力對於Cr3+螢光光譜之影響 28
第三章 近場掃描式光學顯微鏡原理 32
3.1近場掃瞄光學顯微鏡之原理 32
3.2近場掃描光學顯微鏡之光侷限機制 35
3.3 NSOM及AFM之高度維持機制 37
3.3.1 AFM之高度維持機制 37
3.3.2 NSOM之高度維持機制 48
第四章 Cr:YAG雙纖衣晶體光纖生長及近場光學量測樣品之製備 52
4.1 Cr:YAG雙纖衣晶體生長架構及方法 52
4.2 近場光學量測樣品之製備 59
第五章 Cr:YAG雙纖衣晶體光纖之近場光學量測及結構分析 63
5.1 Cr:YAG雙纖衣晶體光纖之成分分析 63
5.2 Cr3+近場光學量測及微結構分析 67
5.2.1纖心內應力與光譜物性比較 67
5.2.2 内層纖衣之奈米晶體近場光譜與其微結構
81
5.3 Cr4+近場光學量測與分析 90
5.4 Cr:YAG雙纖衣晶體光纖之螢光Cr3+和Cr4+螢光
99
第六章 結論 102
參考文獻 103
中英對照表 108

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