液晶與高分子混層結構之雙波混合效應

用雙波混合實驗技術，吾人證實液晶摻雜碳奈管與兩高分子光導層之混層結構擁有極高的繞射效率，其值高達47%，遠超過Raman–Nath理論的極限值（34 %）；同時由於耦合增益的產生，該實驗也證明此樣品結構具有光折變效應。由本研究得知，樣品的增益係數對於電壓及光場強度都分別有其最佳的對應值：我們發現光耦合效應和兩寫入光的總功率呈現正向的關係，同時兩光功率比例越大效果越好；除此之外，在一定總光功率（160 mW）條件之下，隨著總光能量的增加，光耦合增益也隨之增加。此外我們也粗略證明了兩項特性：一、在有經過定向摩擦處理的樣品中，只要我們能使樣品靜置一段時間使其穩定排列，不論我們如何注入液晶均能得到類似的性能；二、不同莫耳分子量的高分子光導層，其繞射效率並沒和高分子光導層的莫耳分子重成一定的關係，但莫耳分子量越大時其耦合增益越小。

關鍵字

碳奈管；高分子光導層；液晶

並列摘要

By using the method of two-beam coupling, we have shown that the mixture structure of carbon-nanotube-doped liquid crystals (LCs) and two polymer photoconducting layers shows quite high diffraction efficiency, up to 47%, which is far beyond the theoretical limit of 34% predicted by the Raman-Nath theory. In addition, such a structure has been shown to exhibit photorefractive effect, due to the presence of two-beam coupling gain. Based on our study, the gain constant of the sample attains highest values corresponding, respectively, to the strengths of the voltage and the light beam. We found that the two-beam coupling gain has a positive trend with the total power of the two writing beams and that the effect gets better with the increasing of the power ratio of the two beams. Moreover, under the condition that the total power is fixed to be 160 mW, the two-beam coupling gain increases as the total energy of light increases. We also roughly proved two characteristics. First, the samples which were rubbed and were laid for a period of time for the LC molecules to reach a stable alignment have similar behaviors regardless of the direction in which the LCs were injected into. Second, there is no obvious relationship between the diffraction efficiency and the molecular masses of polymers of the photoconducting layers. However, the larger the molecular mass, the lower the two-beam coupling gain.

並列關鍵字

carbon nanotube ； photoconducting layer ； liquid crystal

參考文獻

[26] 葉昇龍，《線狀液晶摻雜碳奈管的光耦合效應》，碩士論文，私立中原大學，民國90年。

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液晶與高分子混層結構之雙波混合效應

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