Study On The Photonic Crystaleffects Of Cholesteric Liquid Crystal

Cholesteric liquid crystals are the ones of a naturally forming periodic structure, and theyhave the characteristics of photonic crystals. It will be play a significant rule in opticalcommunication. In this paper, we did some research on the photonic crystal effect of cholestericliquid crystals, such as:Firstly, we studied the theory of photonic crystals and liquid crystals to introduce the basicphotonic crystal theory of liquid crystals. It contains the methods of simulating the liquid crystalswith periodic structure, the theory of forming photonic band gap by Maxwell equations, theoptical properties of the photonic liquid crystals and the theoretical derivation of transfer matrixof cholesteric liquid crystals in planar texture.Secondly, in this paper we introduced the Bernard effect of a cholesteric liquid crystalwhich also named periodic gridlike deformation in temperature field. When the sample ofcholesteric liquid crystal in planar texture was prepared, the sample texture changed withtemperature field and had a two-dimensional structure like pane grate of which the periodicstructure were10μm. The phenomena of Bernard effect we observed showed that thetemperature field induced the liquid crystal molecule convection, the birefringence interferencewas occurred, and liquid crystal director distribution varied periodically. We then used the theoryof Rayleigh-Bénard convection in fluid dynamics to study the two-dimensional periodic structureof the liquid crystal. Compared with Helfrich effect, we could know the mechanism of pane grateeffect in temperature field.At last, given the three dimensional photonic crystal of liquid crystal in blue phase, wefound that liquid crystal with Bernard effect which had two dimensional photonic crystalstructure would be widely used. And then we prepared one dimensional photonic crystal samplesof cholesteric liquid crystal in planar texture to study the photonic band gap effect. After that wetried to do experiment on its application. The meaning of this paper was the first mention of Bernard effect in cholesteric liquidcrystal. It showed there was a two-dimensional periodic structure in Bernard effect. Qualitativeanalysis was studied to show the mechanism of this effect. And the paper also elaboratessystematically the photonic crystal effects of cholesteric liquid crystal. By doing this we couldenrich our knowledge of liquid crystal experiments and cholesteric liquid crystal material.Meanwhile we laid a foundation of future research and application.