Bragg reflection properties of electrically controlled helix distortion in cholesteric liquid crystals

The optical properties and the change of Bragg reflected light intensity of the cholesteric liquid crystal in planar texture induced by helix distortion were studied when the applied electric field was perpendicular to the direction of the helical axis. Using LCD matrix optics, Jones matrix method, and Matlab matrix calculation software, reflectance spectra characteristics were analyzed and numerically calculated. According to the numerical and experimental results, the center wavelength of reflected light does not change with voltages and the Bragg reflected light intensity decreases with the increasing voltage. A model of field induced helix distortion was proposed to give the reasonable explanation on the experimental and numerical results. It is also found that the theory for designing the LCD with color change using electrically controlled helix distortion is not feasible.