Quasi-stable nematic liquid crystal director reorientation under the influence of focused Gaussian laser beam and electric fields

For liquid crystals with positive dielectric anisotropy a torque is generated in the liquid crystal to align the highest polarizability with the electric field, in order to get an equilibrium with minimal energy density in the system. Director reorientation due to the laser beam and electric fields We report on the generation of quasi-stable domains (Fig. 1) in nematic liquid crystal due to the combined influence of optical and electric fields. The generated domains are an order of magnitude larger than the size of the optical field profile due to a leverage mechanism. To achieve the formation of quasi-stable domains with opposite tilting with respect to the rest of the cell, the optical field needs to be applied first. The final reorientation strongly depends on the starting conditions and properties of this optical field. It reverses the pre-tilt and an additional application of the voltage amplifies it dramatically. The resulting reorientation of the director due to the joint influence of the focused Gaussian laser light and the electric field leads to an unusual refractive index profile which itself causes lensing effects. Our experiments confirm the concept of competitive switching when simultaneously electrical and optical torques are present in a nematic liquid crysta

Light-controlled reorientation of nematic liquid crystal driven by an electric field

The joint influence of optical and (quasi-)static electric fields on the orientation of liquid crystal gives rise to peculiar effects. In this article we report on the generation of transient domains in liquid crystals, which are an order of magnitude larger than the size of the optical field profile. The formation of such a domain is due to the fact that the initially present optical field reverses the pre-tilt, and the voltage that is then applied gives rise to an amplification of the tilt angle. The resulting reorientation of the director strongly depends on the starting conditions of the preliminary present optical field. We demonstrate different switching conditions, depending on the relation between the incident angle of the beam and the pre-tilt angle. The resulting refractive index profiles give rise to lensing effects

Observation of symmetry breaking in photoalignment-induced periodic 3D LC structures

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