标题: | 聚合物分散型液晶之光学相位研究 A Study of Optical Phases in Polymer-Dispersed Liquid Crystals |
作者: | 王瀞翊 林怡欣 陈琼华 Wang, Jing-Yi Lin, Yi-Hsin Chen, Chyong-Hua 光电工程研究所 |
关键字: | 聚合物分散型液晶;光学相位;克尔效应;孔洞大小;Polymer-dispersed liquid crystals;Optical phases;Kerr effect;Droplet size |
公开日期: | 2017 |
摘要: | 偏振无关之液晶相位调制器有许多光学应用,目前偏振无关之液晶相位调制器主要分为:1)双层型2)剩余型3)双层+剩余混合型,及4)电场引发之克尔效应型。本实验室在2015年发表的文章中提出另一种混合型偏振无关之液晶相位调制器:奈米型聚合物分散型液晶(domain~250nm)的光学相位来源为液晶分子转动与电场引发之克尔效应,但是由先前的实验结果,克尔效应造成的相位远小于液晶分子转动之偏振无关相位。本论文研究动机为:在奈米型聚合物分散型液晶中,克尔效应之相位是否永远小于液晶分子转动之相位?还是两者相位有可能达到相近的大小?藉由研究此问题,我希望可以更加了解奈米型聚合物分散型液晶中,液晶在外加电场下的转动与光学相位的关系。 本文提出在尺度够小(~200nm)的奈米型聚合物分散型液晶中具有一种混合型的偏振无关相位,此混合型的偏振无关相位包含两种相位:1)外加电场引发的克尔效应造成之相位与2)外加电场下,液晶分子在高分子包围的液晶球中转动所造成之相位。外加小电场下,入射光会先感受到克尔效应造成之相位;当电场逐渐增加,克尔效应的相位会消失,取而代之的是由液晶分子转动所造成之相位。根据实验结果,液晶球尺寸在200nm左右时,克尔效应之相位约为0.1π(径度),但转动造成之相位可从0.24π(径度)~ 0.42π(径度),此相位与奈米型聚合物分散型液晶之相分离程度有关。当尺度超过~350nm的奈米型聚合物分散型液晶中,不存在克尔效应造成之相位,完全都是由转动造成之相位,相位可从0.22π(径度)~ 0.63π(径度)。 由此研究我们可得知在奈米型聚合物分散型液晶中,克尔效应之相位与液晶分子转动之相位取决于液晶球之大小,此两种相位在某些条件下是可能达到数量级接近的。并且我们得知克尔效应之相位发生在临界电压(Threshold voltage)之前,接着外加大电压时,液晶开始转动使得克尔相位消失。 There are many applications using polarization-independent LC phase modulators. Many researches proposed polarization-independent LC phase modulators, such as 1) double-layered type, 2) residual phase type, 3) combination of double-layered and residual phase type and 4) Kerr effect type. In 2015, we proposed a new type of polarization-independent LC phase modulator in nano-PDLC(droplet size~250 nm) which indicates the optical phases come from LC orientation and Kerr effect-induced birefringence. According to previous results, optical phases coming from Kerr effect is much smaller than the one coming from LC orientation. Hence, in this paper, we would like to investigate that in nano-PDLC, is it possible to make optical phases coming from Kerr effect be the same order compared with the optical phases come from LC orientation? In this paper, we proposed that the polarization-independent optical phases in nano-PDLC can be divided into two categories. 1) For droplet size about 200 nm, the optical phases come from LC orientation and Kerr effect. Under small voltages, Kerr phase dominates. With increasing voltages, optical phases come from LC orientation instead of Kerr effect. According to experimental results, Kerr phase is around 0.1π(rad) and orientational phase ranges from 0.24π(rad)~ 0.42π(rad). 2) For droplet size larger than 350nm, the optical phases come from LC orientation, without any Kerr phase. Through this research, we concluded that in nano-PDLC, Kerr phase depends on the droplet size. Under certain conditions, Kerr phase and orientational phase can compete. We also concluded that Kerr phase occurs before threshold voltage. After threshold voltage, orientational phase increases and Kerr phase gradually disappears. |
URI: | http://etd.lib.nctu.edu.tw/cdrfb3/record/nctu/#GT070350513 http://hdl.handle.net/11536/140647 |
显示于类别: | Thesis |