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研究生：	陳錦慧 Chen, Chin-Hui
論文名稱：	利用Z-scan技術研究偶氮染料掺雜液晶聚合物之非線性光學性質 Nonlinear optical properties of azo-dye-doped polymer dispersed liquid crystal films using Z-scan technique
指導教授：	傅永貴 Fuh, Y.G. Andy
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
論文出版年：	2008
畢業學年度：	96
語文別：	中文
論文頁數：	120
中文關鍵詞：	偶氮染料掺雜液晶聚合物、非線性光學
外文關鍵詞：	Z-scan, nonlinear optical property, PDLC
相關次數：	點閱：79 下載：5
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本論文利用Z-scan技術研究奈米液晶球之偶氮染料掺雜聚合物液晶薄膜(azo-dye-doped polymer dispersed liquid Crystal, ADDPDLC )之非線性光學性質。Z-scan 技術只需使用單一光束和簡單的實驗架設，就可以量測材料的非線性吸收係數與非線性折射係數，即光學柯爾常數的高靈敏技術。Z-scan技術量測光學柯爾常數的原理是基於樣品的非線性折射率會產生自聚焦或者自發散現象，利用自聚焦或者是自發散的結論推論其相位及折射率的變化。我們首先使用Z-scan技術量測到偶氮染料掺雜液晶薄膜(azo-dye-doped liquid crystal，ADDLC)具有很大光學柯爾常數，其造成原因是熱效應和染料同分異構化效應。藉由環境溫度的改變，我們可調控偶氮染料掺雜液晶薄膜(ADDLC)的光學柯爾常數。再使用Z-scan技術量測奈米尺寸ADDPDLC樣品的光學柯爾常數，同樣地，藉由不同環境溫的改變，也可以調控奈米尺寸ADDPDLC樣品的光學柯爾常數。實驗結果顯示在環境溫度為35度時，可以量測到最大的光學柯爾常數，這是由於液晶相變點從純液晶之61度提前至約43度。

This thesis explores the nonlinear optical properties of nano-sized liquid crystal droplets azo-dye-doped polymer dispersed liquid crystal（ADDPDLC ) films using Z-scan technique, which is a simple but powerful technique to measure the optical Kerr constant of materials. The measurement of the optical Kerr constant using Z-scan technique is based on the principle of spatial beam distortion due to the self-focusing or self-defocusing that are associated with the intensity-dependent refractive index of the material. Firstly, the nonlinear refractive index of azo-dye-doped LC film is investigated using the Z-scan technique. The results indicate that the optical Kerr constant (n2) of this material is large resulting from the thermal effect and photoisomerization effect. Thus, the optical Kerr coefficient n2 of azo-dye-doped LC film can be modulated by changing the temperature of the sample. In addition, the optical Kerr coefficient n2 of the azo-dye-doped nano-sized PDLC film at various temperatures is also measured using Z-scan technique. The maximum n2 of the azo-dye-doped nano-sized PDLC film is at~ 35 oC.The cause is due to the decrease of clearing temperature of ADDPDLC films. The clearing temperatures for the liquid crystal (E7) used in this work, and ADDPDLC are found to be 61 oC and 43 oC , respectively.

第一章	液晶簡介
§1-1  前言………………………………………................1
§1-2  液晶定義………………………………………………………1
§1-3  液晶分類………………………………………………………3
1-3-1  盤狀分子(disk-like molecules)…………………………4
   1-3-2  棒狀分子(rod-like molecules)………………………5
§1-4  液晶特性………………………………………………………11
1-4-1  液晶的光學異向性(optical anisotropic)………………11
1-4-2  液晶的介電異向性…………………………………………17
1-4-3  溫度對液晶的影響…………………………………………19
1-4-4  液晶的連續彈性體理論……………………………………20
1-4-5  Freedericksz Transition…………………………………22


第二章	理論
§2-1  PDLC薄膜………………………………………………………23
2-1-1  聚合物反應過程……………………………………………23
2-1-2  PDLC薄膜分類………………………………………………25
2-1-3  PDLC工作原理………………………………………………27
§2-2  光引致分子轉向效應………………………………………29
2-2-1  正力矩效應(positive torque effect)…………………29
2-2-2  負力矩效應(negative torque effect)……………….…31
2-2-3  光激發同素異構化效應(photo-isomerization)…………32
2-2-4	光化學相變與光致熱效應…………………………………33
(photochemical phase transition and light-induced thermal effect)
2-2-5	光折變效應(photo refractive effect)………………34
§2-3  Z-scan Techniqe……………………………………………36
2-3-1	  馬克斯威爾方程式…………………………….………36
2-3-2	  Z-scan的非線性折射係數與非線性吸收係數…………41
2-3-3	  Z-scan的理論……………………………………………46

第三章樣品準備與光路架設
§3-1  實驗樣品的準備……………………………………………52
3-1-1	材料介紹………………………………………………52
3-1-2	樣品製作………………………………………………56
§3-2  配向之檢測………………………………………………61
3-2-1光學顯微鏡目測法…………………………………………61
3-2-2聚光干涉儀(conoscopy)…………………………………62
§3-3  觀察樣品細微結構和相變點之分析儀器…………………………64
3-3-1掃瞄式電子顯微鏡(scanning electron microscope.……………64
3-3-2熱示差掃描卡量計（differential scanning calorimeter）…66
§3-4  實驗光路的架設………………………………………69
3-4-1空液晶盒的厚度量測…………………………………69
3-4-2製作ADDPDLC cell的實驗裝置………………………72
3-4-3實驗樣品的吸收光譜和線性吸收係數αo之量測…….….73
3-4-4 測量非線性吸收與非線性折射的Z-sczn 實驗裝置…………76
3-4-5 測量染料G239轉向的pump-probe實驗裝置………………76

第四章	實驗結果與分析
§4-1  ADDPDLC的掃描電子顯微鏡(SEM)和偏光顯微鏡影像
4-1-1	掃描電子顯微鏡(SEM)影像…………………………79
4-1-2	偶氮染料掺雜液晶聚合物薄膜樣品的偏光顯微鏡影像…80
§4-2  ADDPDLC的Z-scan測量………………………………………80
§4-3  E7+G239的z-scan測量………………………………………83
4-3-1	E7水平配向的z-scan測量………………………………83
4-3-2	E7+G239的Z-scan測量…………………………………84
§4-4  NOA81 (99 wt％)+G239 (1 wt％)沒配向的Z-scan測量……96
§4-5  ADDPDLC的Z-scan測量現象之解釋…………………………98
4-5-1	液晶的thermal effect…………………………………98
4-5-2	液晶相變點提前—DSC…………………………………100
4-5-3	染料G239本身貢獻的熱效應…………………………102

第五章	結論與未來展
5-1 實驗結論………………………………………………………103
5-2 未來展望………………………………………………………103
參考文獻……………………………………………………………105
                                    

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