Optically Reconfigurable Reflective/Scattering States Enabled with Photosensitive Cholesteric Liquid Crystal Cells

Circularly polarized light is employed to write information into cholesteric liquid crystal (CLC) cells that initially exhibit homogeneous planar alignment and are fabricated with a photoaligning boundary layer. Overlap of the writing beam with light reflected from the CLC phase disrupts the reflective Grand-jean texture, resulting in a localized region that strongly scatters light. These scattering areas can be geometrically patterned using circularly polarized light and a mask, erased and brought back to the original reflective condition by exposure to linearly polarized light, and then repatterned with a different mask using circularly polarized light. The light-induced scattering is localized to the side of the cell being exposed. Within the scattering region a microscopic texture is formed, which exhibits an average feature, or "domain", size related to cell thickness and helical pitch. The behavior occurs only when the CLC and incoming writing radiation exhibit the same handedness and when the reflection bandwidth of the CLC is commensurate with the wavelength of the incoming radiation. This new phenomena provides the ability to reconfigure reflectivity from a CLC cell and is expected to be useful for systems where all optical control of dynamic information is needed.