雷射治療是非侵入性療程，依據不同的雷射輸出波長，具有不同的療效，然而目前於雷射治療中所使用的雷射光源多為單一波長，實用性受到相當大的限制。因此我們提出利用膽固醇液晶易於調控的特性，來設計與製作具有體積小、低成本與可調式的膽固醇液晶光纖雷射元件。

膽固醇液晶為二維的光子晶體，具有光子能隙，當入射的光波長落在能隙邊緣時，其群速度為零相當於空間中產生駐波，因此膽固醇液晶可用來作為雷射的共振腔，於液晶中再添加合適的增益介質及激發光源即可輸出雷射，而膽固醇液晶的光子能隙可容易的藉由外場改變，具有高度的調控性。本論文將膽固醇液晶與光纖結合製做膽固醇液晶光纖雷射，利用膽固醇液晶易於調控的特性來達到具有高調控性的光纖雷射。

本研究論文分成膽固醇液晶光纖雷射元件製作、元件光學特性量測、改善元件特性與量測雷射輸出可調控的範圍。首先使用兩端已經由配向處理的多模光纖與填入摻有雷射染料膽固醇液晶的空芯光纖來製作膽固醇液晶光纖雷射元件；外接白光光源並由光譜分析儀量測此元件的穿透光譜，來觀察此元件的配向好壞；再藉由Nd:YAG 脈衝雷射做激發光源，來觀察雷射的輸出特性；最後再將元件升溫，觀察此元件的雷射輸出在溫度改變時具有多少的調控性。

Laser therapy has a great attraction in past decades because of healing faster, less pain and less swelling. The different wavelength of laser sources is used for different treatment. However, the tuning range of laser wavelength in laser therapy is narrow so far. So, we propose the “cholesteric liquid crystal based tunable fiber laser" device to achieve compact size, low cost and tunable laser.

Cholesteric liquid crystal is a 2D periodic strcucture so it is a photonic crystal and there is photonic bandgap in it. When the frequency of incident light locates at the photonic band edges of cholesteric liquid crystal, the velocity of incident light comes to zero. Then, by adding some laser dye into the CLC material and applying external force, there would lase in the mixture of CLC and laser dye. In this thesis, we formulate the CLC fiber laser device and measure the optical property and tunability of laser wavelength.

The CLC fiber laser is formulated by CLC (nematic E48 and S811) with adding some laser dye DCM, two pieces of multi-mode fiber and hollow core fiber. However, It’s hard to do a good alignment film at the fiber ends, so the multi-domain of CLC planar texture results in multi-peak lasing output. The multi-mode fiber at incident way uses single-mode fiber to instead. The pumping spot size of SMF is small enough to see the single domain so the output lasing signal would be single mode. Additionally, The temperature controlled tunability of cholesteric liquid crystal fiber laser(SMF in, MMF out) is 22 nm.

論文審定書 i
摘要 ii
Abstract iii
目錄 iv
圖目錄 v
第一章 簡介 1
1-1液晶介紹 1
1-2液晶的分類 2
1-3液晶的物理特性 5
第二章 理論介紹 11
2-1膽固醇液晶簡介 11
2-2雷射原理簡介 16
2-3光子晶體簡介 18
2-4膽固醇液晶能隙邊緣型雷射 19
第三章 實驗方法與過程 20
3-1材料介紹與材料配製 20
3-2光纖雷射元件製作 24
3-3量測雷射訊號 25
第四章 結果與討論 26
4-1配製膽固醇液晶 26
4-2添加雷射染料與膽固醇液晶光纖雷射元件製作及量測 29
4-2.1膽固醇液晶添加雷射染料Py597 29
4-2.2膽固醇液晶添加雷射染料DCM 32
4-3探討雷射輸出為多根模態的成因 38
4-4改變製程以達到單根模態的雷射輸出 41
4-5可調控範圍 45
第五章 結論與未來展望 46
參考文獻 47

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