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本實驗使用向列型液晶(E7)摻雜偶氮染料(methyl red)製作具晶格圖斑之繞射光柵。我們利用偶氮染料吸收特定波長(532 nm)的光後吸附在基板並帶動液晶轉動，配合中心點加一的六孔洞光罩(Q=6+1)及光學設備所形成的各種不同的干涉結果，將干涉圖案記錄在摻雜染料的液晶樣本中製作出具晶格圖斑之液晶繞射光柵。干涉結果具三維晶格圖斑的特性，在不同光路位置時可以有不同的干涉圖斑，透過改變紀錄位置，可以得到不同的晶格圖斑光柵，並觀察樣本的繞射特性。另外透過三孔洞光罩(Q=3)搭配一個90°TN樣本，得到類似三維各向異性的干涉結果。使用氦氖雷射(632.8 nm)觀察樣本的繞射現象，及觀察對樣本施加不同電壓時繞射光柵的變化，量測對樣本施加不同電壓下繞射效率的變化，另外也使用檢偏器檢測不同入射偏振光經過樣本後的繞射點偏振性。此實驗除了驗證利用光束干涉可在不同距離下得到不同的晶格圖斑之液晶光柵外，也可以透過此架構達到許多不同的具三維結構圖斑的液晶光柵，可變化性豐沛。

In this study, the diffraction gratings with crystalline patterns and their electro-optical characteristics in the azo-dye doped liquid crystal (LC) cells were studied. The adsorption technique of azo dyes on the substrate by absorbing light of a specific wavelength (532 nm) were used, which cause the LCs near the substrate to rotate to parallel to the direction of azo dyes. We combined with the adsorption technique and the special mask to record the crystalline patterns in the azo-dye-doped LC cells to form diffraction gratings. The mask was precisely fabricated to have six small apertures regularly distributed on a circle and a small hole on the center. Gratings with different crystalline patterns were fabricated by recording the patterns in different z positions. The diffraction characteristics of these LC grating were studied. Furthermore, a 90° TN sample and the other mask with three small apertures regularly distributed on a circle were used to fabricate a grating with three-dimensional LC alignment structure for advanced control of polarized beams. The helium-neon laser (632.8 nm) was used to observe the diffraction phenomena of the LC sample. In the experiments, the variation of diffraction efficiencies with voltages applied to the sample was observed. The polarization conversion properties from the LC grating were also studied.

摘要...i
Abstract...ii
誌謝...iii
目錄...iv
表目錄...vi
圖目錄...vii
符號說明 x
第一章 緒論...1
第二章 液晶簡介...2
2.1 液晶的發現...2
2.2 液晶的定義...2
2.3 液晶的分類...3
2.3.1 盤狀分子...3
2.3.2 棒狀分子...4
2.4 液晶物理...8
2.4.1 液晶的光學異向性(optical anisotropic)...8
2.4.2 液晶的介電異向性...10
2.4.3 溫度對液晶的影響...12
2.4.4 液晶的連續彈性體理論...13
2.4.5 Freedericksz Transition...13
第三章 相關理論...14
3.1 偶氮染料的光致同素異構化反應(photoisomerization effect)...14
3.2 光激發染料分子導致液晶旋轉機制...14
3.2.1 正力矩效應(Postive Torque Effect)...14
3.2.2 負力矩效應(Negative Torque Effect)...16
3.3 溝槽理論...17
3.4 繞射(Diffracting)...17
3.5 晶格圖斑...18
3.6 三維晶格圖斑...19
3.7 瓊斯矩陣(Jones Matrix)...20
3.8 三維各向異性干涉的結構...21
第四章 材料介紹與實驗架構...23
4.1 材料介紹...23
4.2 樣本製作...25
4.3 實驗架構...26
第五章 實驗結果與討論...30
5.1 三維晶格週期性結構...30
5.2 不同位置的吸附結果...31
5.3 不同圖斑之液晶樣本在加電壓時的偏光顯微鏡圖...32
5.4 不同圖斑之液晶樣本的加電壓對應不同入射偏振繞射圖...34
5.5 不同圖斑之液晶樣本的繞射點加電壓對應繞射效率...39
5.6 不同圖斑之液晶樣本的繞射點與偏振的相關性...41
5.7 不同圖斑之液晶樣本的繞射點出射偏振性...43
5.8 不同圖斑之液晶樣本的繞射點反應時間...45
5.9 三維各向異性結構與其吸附結果...48
5.10 三維各向異性之液晶樣本在加電壓時的偏光顯微鏡圖...49
5.11 三維各向異性之液晶樣本在加電壓時的繞射圖...50
5.12 三維各向異性之液晶樣本在加電壓下的繞射效率...53
5.13 三維各向異性之樣本繞射點對應不同入射偏振的出射偏振性...54
第六章 結論...57
參考文獻...58
Extended Abstract...60

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