Study On The Orientational Photorefactive Effect In Methyl-Red Doped Nematic Liquid Crystal

Nematic liquid crystal is an excellent nonlinear photorefractive material with high performance. In the last decade, it has been investigated extensively. Since the first report of the orientational photorefractive effect in nematic liquid crystals in 1994, the materials have attracted considerable attention for its excellent optical properties recently.The threshold of orientational photorefractive decreases very apparently by doping the material with dye. Therefore doped nematic liquid crystals have be used in many applications. The key problem for holographic storage is to record and reconstruct photorefractive gratings in the material, which is the main work of this paper.First of all, The nematic liquid crystal 5CB cell doped with Methyl-Red 1% by weight was presented, Then we analyze theoretically the orientational photorefractive effect in the nematic liquid crystals, namely the mechanism of grating formation without applied field. The basic optical characteristic is studied. Two beams coupling method was used to measure the first order diffraction efficiency under different experimental conditions, such as the separation angle between writing beams or the intensity, the thickness of the sample, temperature and so on.Optimal experimental conditions were given for the holographic storage by discussing the above diffraction efficiency in details. The holograms are storied under the best experiment conditions. We could get reconstruction of the best hologram and the edge-strengthened hologram. We also stored and reconstructed two holograms. Additionally, we also simply discussed the polarization characteristic of MR/5CB sample with applied magnetic field.