Continuous rotation of a cholesteric liquid crystalline droplet by a circularly polarized optical tweezers

We studied the opto-mechanical response of droplets composed of cholesteric liquid crystal (ChLC) to a circularly polarized optical tweezers. Although the alignment of LC molecular within a droplet depends on the relative ratio of the droplet diameter d to the helical pitch p, the optically induced rotation was found to be asymmetric to the direction of circularly polarized light irrespective to the inner molecular alignment. We studied the rotation of the droplets with various sizes, helical pitch (strength of chirality) and different chirality. In the case of d/p ∼ 1, the direction of the rotation was simply determined by chirality of ChLC and the rotation was also observed for linearly polarized light, which has already been reported by Yang et al.