水平排列線狀液晶盒中液晶向擾動之散射干涉圖樣

Abstract

本論文的主旨是在探討於水平排列線狀液晶盒中所發現新散射現象，此新現象主要是觀察由散射光所引起的干涉圖樣；實驗中我們發現這些干涉圖樣在不同外場（電場或光場）時會有著不同的外觀，簡單地來說，圖樣的外觀形狀可被歸類為環狀、近似橢圓狀與近似雙曲狀，而且這些干涉圖樣會隨著我們所加的外場面產生周期性的變化；除此之外，我們亦發現出射光功率隨著電場或光場之增加而改變。 除了在實驗上所觀察與記錄之干涉圖樣的改變外，在理論上，我們亦對處於低電場時，所觀察到的環狀干涉圖樣，利用相位差造成建設性干涉與破壞性干涉的觀念，做了一個簡單的推導，這個想法可以用來解釋環狀干涉圖樣所形成的原因，以及環狀圖樣隨電場改變時所相對應之變化趨勢。

The major purpose of this thesis is to study a new phenomenon of light scattering from a planar aligned nematic liquid-crystal film. The new phenomenon we observed in the experiment is the optical patterns caused by the interference of the scattering light . When Ar-ion laser transmitted the planar aligned nematic liquid-crystal film sandwiched between a pair of crossed polarizers, some different interference patterns occurred periodically with the applied external-field changing. Roughly speaking, the geometry of those interference patterns look like ring 、ellipse-like or hyperbola -like. In our experiment the applied external -field (λ=514.5nm). Besides the geometry of interference patterns will periodically change, the power of output light also varied with applied external field increasing. In this thesis we also derived a simple mode to explain the formation of ring patterns and the influences of the applied electric field on these ring patterns under the lower electric field .