Periodic structures generated by light in chiral liquid crystals.

We discuss materials that reveal fundamental intercoupling of light and chirality in creation of complex structures. These materials are based on cholesteric liquid crystals (CLCs) photosensitized by azobenzene nematics. Transformation of the one-dimensional periodic structure of such CLCs into complex spatial patterns takes place on macroscopic scales, over the whole area of the CLC layer, under the influence of low power radiation including LED, ambient illumination, and sunlight. The obtained structures, with their origin in the strain of the CLC layers caused by trans-cis photoisomerization precede a shift in the bandgap position of the CLCs. The effect is observed both in red-shifting as well as blue-shifting CLCs.