偶氮材料(如偶氮苯、偶氮染料)所具有的異向性在近幾年中受到科學家們高度的重視並積極地研究，並且將其應用在液晶元件的光配向技術上。在這之中，偶氮染料摻雜在高分子薄膜中，利用激發光使偶氮染料引致液晶分子排列的應用在這幾年來亦受到極度的重視，此即為光配向效應。在光配向效應於本系統的應用中，許多光學元件，如顯示器、全像光柵、透鏡、濾波片、偏振片等已被研究發展出來。此光配向技術中最主要的機制莫過於光引致染料分子排列，總括來說這個機制起因於以下幾個效應：正/負力矩效應、光致同素異構化效應等。本論文將提出偶氮染料摻雜在高分子薄膜中之光配向效應。主要目標為研究偶氮染料摻雜於高分子薄膜中所發生的有趣物理現象與研發可控制之全像元件的製造及其應用，其包含兩個研究主題，其一為偶氮染料摻雜於高分子薄膜中之液晶光配向機制；另一為偶氮染料摻雜於高分子薄膜中之二維全像光柵的製作及其繞射特性研究。

本論文的第一部份研究偶氮染料摻雜於高分子薄膜中光配向之機制，我們提出一個理論模型來模擬兩種不同形式的扭轉光柵，並利用光配向機制製作出相應的扭轉光柵，接著對其繞射偏振特性進行研究，理論模擬與實驗結果相當吻合。此外，由另一部份的實驗，我們證明了此光配向薄膜具有可複寫之特性，對於元件的應用上具有相當大的價值。

第二部分的研究是有關於二維全像光柵的形成及其繞射特性之研究，我們成功地將一維全像光柵寫入摻雜偶氮染料之高分子薄膜上，並垂直疊合兩個一維全像光柵基板以形成二維全像光柵。接著利用瓊斯矩陣與傅立葉轉換模擬出此二維光柵在偏光顯微鏡下所觀察之影像與雷射通過光柵後之繞射偏振影像，理論模擬與實驗結果相當吻合。

Azo materials, such as azobenzene, azo dyes and others have been investigated extensively in recent decades. Several researchers use such materials to develop photo-alignment techniques for liquid crystal devices because of their particular anisotropic optical properties. Azo dyes in a dye-doped polyvinyl alcohol (PVA) film are re-orientated using a single pump beam, inducing the reorientation of liquid crystals. This so-called photoalignment effect has attracted much interest over recent years. Many optical devices, including displays, holographic gratings, optical lenses, optical filters, polarizers and others, have been developed in this system. The primary mechanism of this photoalignment effect is the light-induced reorientation of dye by the positive/negative torque effect or photoisomerization effect. This thesis studies the photoalignment effect, which is caused by pumping a laser beam in an azo-dye-doped PVA film. The aims of the thesis are to examine the related physics and the fabrications and applications of controllable holographic devices. The thesis considers two topics; the first is the mechanism of photoalignment in azo-dye-doped PVA film, and the other is the fabrications and diffraction characteristics of a two-dimensional holographic polarization grating in azo-dye-doped PVA films.

The first part of this thesis investigates the mechanism of photoalignment in azo-dye-doped PVA film. This work proposes a theoretical model to simulate two twist nematic (TN) gratings. Such TN gratings are fabricated by exploiting the photoalignment effect and the polarizations of the diffracted beams are analyzed. The experimental results agree well with the theory. Moreover, the rewritability of this azo-dye-doped PVA film is demonstrated, and has an extensive range of applications for optical devices.

The second part of the thesis discusses the formation and diffraction characteristics of a two-dimensional holographic polarization grating. A two-dimensional holographic grating is fabricated by orthogonally overlaying two 1D polarization holograms. The images obtained under a polarized optical microscope (POM) and the diffraction patterns from the 2D grating are simulated using the Jones matrix and Fourier transformation. The experimental results agree well with the theory.

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