本論文利用薩格涅特干涉儀進行光配向製作聚焦效率與焦距可調的菲涅爾液晶透鏡。激發光經由薩格涅特干涉儀產生類菲涅爾圖案後，照射於偶氮染料與液晶的混合材料中，在受光區域的染料分子會產生光致異構化效應而形成光配向，染料分子在進行一連串的trans與cis反應後，會誘導液晶分子的排列方向最終與激發光的偏振方向垂直，造成樣品中受光奇數區與不受光偶數區的液晶具有不同排列結構，使得偵測紅光通過樣品後會因相鄰兩區間結構不同產生的相位差異而形成聚焦效果。此菲涅爾液晶透鏡可利用外加電壓的方式調控聚焦效率的變化，實驗結果顯示當施加電壓為3.1 V時，透鏡的聚焦效率可達31.5 %。另外，此透鏡樣品的光配向效果可經由加熱的方式抹除，並重新寫入新的類菲涅爾圖案，達到可複寫的效果。

This study presents a focusing efficiency and focal length tunable Fresnel lens with liquid crystals fabricated by a Sagnac interferometer. When the Fresnel-pattern green beam, formed by the Sagnac interferometer, is irradiated on the azo-dye doped liquid-crystal mixture, the azo-dye molecules will undergo the trans-cis photoisomerization and then generate photo-alignment effect in the bright (odd) zone, which results that the direction of liquid-crystal molecules will perpendicular to the linearly polarized pump beam. The various structures of liquid crystals in the odd and even zones will produce the phase difference, resulting in a Fresnel lens generated. The focusing efficiency of proposed Fresnel lens can be controlled by the external AC voltages. The experimental results show that the focusing efficiency can reach its maximum of 31.5 % under applied voltage of 3.1 V. In addition, the photo-alignment effect of azo dyes can be erased through the thermally method and rewritten by the pump beam with different Fresnel-like pattern, which leads to the Fresnel lens with various focal lengths.

論文審定書 i
致謝 ii
摘要 iii
Abstract iv
目錄 v
圖次 ix
表次 xiii
第一章 簡介 1
1.1 前言 1
1.2 液晶簡介 2
1.2.1 液晶的發現 2
1.2.2 何謂液晶 2
1.3 液晶的分類 3
1.4 液晶物理 9
1.4.1 光學異向性 9
1.4.2 介電異向性 12
1.4.3 彈性連續體理論 13
1.4.4 液晶配向 14
1.4.5 Freedericksz transition 15

第二章 相關理論 17
2.1 偶氮染料 17
2.2 光配向機制 17
2.2.1 photo-isomerization 17
2.2.2 photo-crosslink 18
2.2.3 photo-degeneration 18
2.3 光引致液晶分子轉向效應 19
2.3.1 正力矩效應 19
2.3.2 負力矩效應 21
2.3.3 吸附效應 22
2.4 賓主效應 23
2.5 菲涅爾透鏡 23
2.5.1 菲涅爾透鏡的理論 23
2.5.2 相位型菲涅爾透鏡的理論 24
2.6 薩格涅特干涉儀 28

第三章 樣品製作與儀器架設 29
3.1 材料介紹 29
3.2 樣品製作 31
3.2.1 偶氮染料摻雜液晶 31
3.2.2 液晶樣品製作 31
3.3 實驗架設 32
3.3.1 具類菲涅爾圖案之激發光的光學分析 32
3.3.2 探討菲涅爾透鏡之焦點強度隨時間變化的關係 33
3.3.3 觀察樣品在偏光顯微鏡下的光學變化 34
3.3.4 探討樣品聚焦隨施加電壓的變化 34
3.3.5 樣品複寫特性的探討 35

第四章 實驗結果與討論 36
4.1 具類菲涅爾圖案之激發光的光學分析 36
4.2 菲涅爾透鏡之聚焦強度隨激發時間變化的探討 37
4.3 透鏡聚焦效率隨施加電壓變化的探討 40
4.4 菲涅爾液晶透鏡對偵測光偏振的依賴性探討 43
4.5 探討透鏡樣品的複寫特性 44

第五章 總結與未來展望 46
5.1 總結 46
5.2 未來展望 48
參考文獻 49

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