本論文中所進行的實驗是嘗試將液晶做成液晶透鏡,液晶透鏡的研究是一個很有趣的題目,我們可以利用光電場偏振方向與液晶分子方向的不同,所感受到的折射率也隨著不同的原理,把液晶做成類似GRIN Lens的光學元件,其好處就是可以利用外加電場來控制此光學元件的焦距,不像一般的光學透鏡都是固定焦距的。由於之前的論文所做的液晶透鏡大部份都與光電場的偏振方向有關,因此本論文期望以新的結構做出與光電場偏振方向無關的液晶透鏡。本論文中所做的液晶樣品為兩層光軸互相垂直的液晶層所合成的結構。因此不管入射光的電場偏振方向為何,其所感受到的折射率皆約略相等,所以本論文中所做的液晶透鏡是與光電場方偏振方向無關的。液晶透鏡最重要的部份就是要想辦法做出折射率差,使折射率為梯度分佈,如此才能使光線聚焦或發散。本論文所使用的方法是利用圓形蝕刻的方法產生不均勻的電場,所以外圍的液晶分子就會比中間的液晶分子先轉動,因此就能產生折射率差,而且折射率為梯度分佈。
A liquid crystal lens is prepared with two layers of nematic liquid crystal cells. These two layers of nematic liquid crystal cells are homogeneous alignment and the directors are perpendicularly each other. The ITO glass is etched to form a hole-patterned electrode. The curved electric field results the directors are reoriented easily at exterior and gradually difficult in approaching the center. The focal length is variable and is function of applied voltage. In our device, the two perpendicular alignments of two cells can compensate the difference of optical path length, when the incident light has different polarization. The experimental results are conformed to theory.