a dynamic hologram is formed in anisotropic liquid crystal gel materials . by applying an electric field , the orientation of part of the liquid crystals can be altered and the hologram can be turned on and off . using lc gels allows for holographic elements with no diffraction in the voltage off state so that the hologram appears only during application of an electric field . also , the anisotropic lc gels maintain polarization dependence . the dynamic holograms are suitable in e . g . dynamic holographic optical components whereby an optical function can be included / excluded in a beam path without introducing or removing elements .