在本論文中,我們主要所探討的是藉由摻雜偶氮染料(Methyl Read)液晶薄膜，在受光激發引致液晶定向排列產生扭轉配向光柵，進而研究其繞射光之偏振。扭轉配向光柵(TN-grating)的產生是利用光引致摻雜在液晶中的染料分子之吸附效應對液晶產生配向而成。我們實驗室之前學長姐的研究結果顯示，如在液晶中摻雜少許的偶氮染料分子，並使其照射一線偏振之固體雷射(波長約為532nm)，染料分子便因吸附效應而吸附至玻璃基板上，並且使得液晶分子導軸重新排向，實驗觀察顯示液晶導軸與激發光呈近似垂直之配向。因此我們利用一個線條型明暗相間之光罩， 讓線性偏振光擴束後經過光罩再照在摻雜染料分子的水平排列液晶薄膜上。在透光處，由於光致染料吸附對液晶排列產生似扭轉型向列相排列，而在低透光處，無明顯之光配向效應，如此便可形成一個扭轉配向的光柵。對於光柵之繞射光與偵測光的偏振關係，以及在外加不同之電壓下，繞射光之偏振改變的情形做了有系統之量測。接著，我們利用瓊斯矩陣、傅立葉光學和MALAB軟體工具寫出的程式理論分析，發現實驗結果與理論相當吻合，如理論預期，繞射光之光強與入射光偏振無關，且在外加電壓下，TN-grating可作為偏振光分光器。

　　This thesis studies the polarization of diffracted beams from a Twisted-Nematic (TN) grating. The TN grating is fabricated through photoalignment effect in a dye-doped homogeneous liquid crystal film. Experimental results obtained previously in our laboratory show that irradiation of a suitable light in an azo-dye-doped liquid crystal film could induce dye adsorption on the glass substrates. The adsorbed dyes then reorient liquid crystals with their director axes perpendicular to the pump-beam polarization. Based on such a adsorbed-dye alignment effect, we fabricate a TN grating by applying expanded a linearly polarized laser beam (λ 532nm) through a stripe-patterned photo-mask onto a dye-doped homogeneous liquid crystal film. The polarization of the diffracted beam from such a TN-grating under application of various voltages is systematically studied. The experimental results agree well with theory. It is noted that the intensity of the diffracted beam is independent of the polarization of the probe beam as expected. Also, the TN-grating is found to be applicable for as a polarization beam splitter.

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