New solution for broadband geometrical phase liquid crystal devices

Coating water-soluble photoalignment material AbA-2522 on top of the patterned polymerizable liquid crystal (PLC) retarder obtain liquid crystal photoalignment direction at the angle to the direction of the bottom retarder. Combination of single patterned exposure of the bottom photoalignment layer with linear polarized light for orientation of the bottom retarder and non-patterned exposure of the top photoalignment layer with circular polarized light allows fabricating of the patterned top PLC layer that is at every point at 45° degree to the orientation pattern of the bottom PLC retarder. We optimized the PLC layers design in optical simulations with respect to PLC dispersion and obtained a solution that can be equivalently represented as a broadband half-wave retarder (420 to 620nm). The measured polarized transmission spectra are in good agreement with the derived analytical model.