External Electric Fields Action on Liquid Crystalline Layers, Modifying Their Degree of Order (original) (raw)
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2006
The main refractive indices and the birefringence of MBBA and PPMAEBOBA10 -2 g/cm 3 in TCM nematic liquid crystals at room temperature were determined by interferometric means for some visible monochromatic radiations in the absence and in the presence of external electrostatic or alternate electric fields of different frequencies. This study revealed the increase in the degree of order with the magnitude of the electrostatic field acting on the MBBA thin layer at room temperature. The increase in the frequency of the external alternate electric field decreases the order degree of PPAMAECOBA in TCM lyotropic liquid crystal, showing that the dipolar collective interactions of the side chains of polymer are responsible for the liquid crystal nature of this mixture.
Influence of additional electric field on the birefringence of a nematic liquid crystal
Journal of Contemporary Physics (Armenian Academy of Sciences), 2009
⎯Influence of the longitudinal voltage applied along the semiconductor substrate of a planar-oriented liquid crystal cell on the birefringence of a nematic liquid crystal (NLC) was investigated. It is shown that for a fixed magnitude of the transverse field the application of a longitudinal voltage creates an additional possibility to control the electro-optically induced phase incursion of the radiation passing through NLC. Dependence of the phase incursion on the control voltages is obtained. The results of simulation of the longitudinal voltage effect on the NLC reorientation are described. The obtained results can be used in development and designing of NLC phase modulators.
THE BIREFRINGENCE OF THIN FILMS OF SOME NEMATIC LIQUID CRYSTALS
2000
Birefringence and birefringence dispersion of N-(p-methoxy-benziliden)-p-n'-butylaniline (MBBA) as well as of poly-(pheny-methacrylic)-ester of cetyloxybenzoic-acid (PPMAECOBA) in tetrachloromethane (TCM) thin films have been determined. Measurements have been made, at room temperature, by two methods: interferometrically in monochromatic light and from the visible channeled spectra of thin layers. The dependence of the main refractive indices on light wavenumbers has been established using
Journal of Applied Physics, 2011
A simple optical method to measure the electric-field-induced birefringence and Kerr constant of polymer-stabilized blue-phase liquid crystals (PSBP-LC) is demonstrated. By measuring the phase shift of PSBP-LC and the averaged refractive index of PSBP-LC at the voltage-off state, the ordinary refractive index and extraordinary refractive index of PSBP-LC as function of applied voltage can be obtained experimentally. As a result, the electric-field-induced birefringence and Kerr constant can be determined as well. The method we proposed can help in designing PSBP-LC-based photonic devices. V
Optics Express, 2010
We demonstrate a method to directly measure the electric-fieldinduced birefringence of a polymer-stabilized blue-phase liquid crystal (PS-BPLC) composite. The induced birefringence follows the extended Kerr effect well and is approximately 3X the ordinary refractive index change. The measured data are validated by comparing the simulated and measured voltage-dependent transmittance with an in-plane switching cell. The impact of these results to the material optimization of emerging BPLC displays is discussed.
Birefringence measurements of liquid crystals
Applied Optics, 1984
A convenient and accurate technique for measuring the birefringence of liquid crystals at discrete wavelengths or as a continuous function of wavelength in the ultraviolet, visible, or infrared spectral regions is described. The method is based on determination of the phase differences which occur when monochromatic polarized light propagates through a medium with an anisotropic refractive index. Birefringence measurements at 0.6328 Am for two liquid crystal materials, BDH-E7 and ZLI-1132, and a continuous birefringence spectrum of ZLI-1132 from 2 to 16 Am are reported. Additionally, a liquid crystal based phase retardation plate which can be voltage tuned and calibrated to provide any degree of phase shift from 0 to 27r over a wide wavelength range (0.4-16 Am) is discussed.