Guided Wave Studyof Reflective MTN Liquid Crystalcell

In recent years, among the developed optical guided wave techniques, the fully leakyguided wave technique has been widely used to study the distribution of director in the liquidcell. This technique is mainly on the basis of the measurement of the reflectivity andtransmissivity of linearly polarized light (p light or s light) with different incident anglesthrough the liquid crystal cell. By using the liquid crystal continuum and the4×4multilayeroptics theory to fit the data of reflectivity and transmissivity, we can obtain the informationabout the director distribution in the liquid crystal cell.In this thesis, the90°reflective-mode MTN (mixed twist nematic) liquid crystal cell,which is used for liquid crystal on silicon (LCOS) display, is studied by using the improvedfully leaky optical guided wave technique. The biggest characteristic of the experimental liquidcrystal cell is that the transparent electrode indium-tin-oxide (ITO) was replaced by aluminumcoating, so there are only four sets of reflective signals: Rpp, Rss, Rps, Rsp. From the results ofexperiment, we found that there are differences between the polarization-conversion signals Rpsand Rsp, which illustrates that the director has small tilt angle on the upper and lower substrates.Then the experiment data were fitted to the modeling predictions from the program based onliquid crystal continuum theory and multilayer optical theory, we finally obtained the detailedinformation of the director. Meanwhile, we also got the related information of different layersof the cell (alignment layer, ITO, aluminum coating), including the optical permittivity and thecorresponding thickness. From the results of best fits, we found that the pre-tilt angle on theupper substrate is different from that on the lower substrate, which suggests that the ITO andthe aluminum coatings have different effects on the alignment layers.