臺灣博碩士論文加值系統

雙丙烯酸酯是一款主鏈型高分子液晶，具有良好的光敏感性，可藉由UV光和加熱產生聚合，常被研究應用於全像紀錄感光材料上。鑒於本實驗室先前的工作發現，雙丙烯酸酯 RM82, RM257能在非主要吸收波段下雷射光源下聚合，並成功記錄了兩道至三道雷射產生的干涉條紋於液晶樣品之中。關於雙丙烯酸酯在紅光下具有良好的光吸收，我們認為是雙丙烯酸酯裡產生了雙光子吸收效應，雙光子吸收為電子在極短的時間內同時吸收兩顆光子能量並躍遷到激發態，且能階的能量差剛好等於兩顆光子的能量和。
本次實驗裡，我們利用Z-scan技術來驗證雙丙烯酸酯的雙光子吸收能力，Z-scan是一款用來量測非線性光學的實驗技術，具有光路簡單而且量測精準的特性，在開孔式的Z-scan實驗下，我們成功的得到雙丙烯酸酯的雙光子吸收截面大小，並證明雙丙烯酸酯是一款良好的雙光子吸收材料。

Diacrylate mesogen is a kind of main chain liquid crystal polymers which has good photosensitive property, can be polymerized using UV-light and heat. It can be used for the holographic recording as the photonsensitive material. In past research, we used long wavelength laser beam to illuminate diacrylate mesogens RM82 and RM257, and found that they were polymerized. It was also found that the laser interference fringes may be recorded in the liquid crystal samples. It was thought that the polymerization of the diacrylates was caused by two photon absorption. However, the evidence that can be used for supporting the inference has not been found. Two-photon absorption is that the electron absorbs two photons in a very short period of time and transitions to the excited state, and the energy of two photons is equal to the energy difference between two energy state.
In this study, we used Z-scan technique to verify the two-photon absorption property of diacrylate mesogen. Z-scan is a simple yet and highly sensitive measurement technology, which can be used to measure nonlinear optical properties. Using the Open aperture Z-scan, we obtained the two photon absorption cross-section of the diacrylate successfully, and verify that diacrylate mesogen is a good two-photon absorption material.

致謝 i
摘要 ii
Abstract iii
目錄 iv
圖目錄 vi
第一章 緒論 1
第二章 液晶簡介 3
2.1物質的相態 3
2.2液晶的分類 4
2.2.1層列型(Smectic) 4
2.2.2向列型(Nematic) 5
2.2.3膽固醇型(Cholesteric) 5
2.3液晶的特性 6
2.3.1秩序參數 6
2.3.2液晶的光學異向性 7
2.3.3液晶的電學異向性 10
2.3.4連續彈性體形變理論 11
第三章 雙光子吸收理論 12
3.1雙光子吸收介紹 12
3.2 馬克斯威爾方程式 14
3.3雙光子吸收的量測 19
第四章 Z-scan技術 21
4.1 Z-scan技術介紹 21
4.1.1背景 21
4.1.2實驗原理 21
4.2開孔Z-scan 掃描雙光子吸收理論 24
4.2.1雷射光在空間中的傳播 24
4.2.2線性穿透與非線性穿透 25
4.2.3穿透率T與雙光子吸收係數之函數關係 27
第五章 實驗過程與結果討論 29
5.1高分子液晶材料介紹 29
5-2液晶樣品製作步驟: 32
5-2-1玻璃基板製備 32
5-2-2製作液晶盒 33
5-3實驗光路的架設: 34
5-4實驗量測方法 35
5-5實驗結果與討論 35
5-5-1 雙丙烯酸酯之Z-scan量測與數據擬合 36
5-5-2 HeNe雷射光場引致雙丙烯酸酯之雙光子吸收特性 40
第六章 總結 41
參考文獻 42
附錄1 使用Labview控制移動平台與示波器偵測Z-scan數據 45

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