Nonlinear optical director reorientation in heliconical cholesteric liquid crystals: a brief review

Cholesteric liquid crystals, also known as chiral nematics, possess a right-angle helicoidal structure with pitch in the submicrometer and micrometer range. Although the possibility of getting optical reorientation in this kind of materials has been considered since the discovery of giant optical nonlinearity in nematic liquid crystals, a significant light-induced modulation of the helical structure has shown to be a challenging task. The recent experimental realization of a chiral phase with an oblique helicoidal structure, identified as the heliconical phase predicted by Meyer and DeGennes in 1968, offers the opportunity to observe such an optical reorientation of the optic axis. This paper is a brief review of the nonlinear optical properties of these unconventional chiral nematic liquid crystals and is aimed at showing that the world of liquid crystalline phases can still amaze with new material properties and new physics.