Light-induced macroscopic chirality in azo-dye-doped polymers

Light-induced macroscopic chirality in a nonchiral azo-dye-doped polymer film is reported. A helicoidal standing wave was used to achieve a twisted molecular organization. Polarization properties of obtained helicoidal Bragg gratings are similar to cholesteric liquid crystals, where the response of the system is different for left and right circularly polarized light. A theoretical analysis with coupled-wave equations is done.