Abstract

Liquid crystals (LC) are composed of rod-like organic molecules. As a result of intermolecular interaction, for specific temperature ranges, these molecules are arranged to have a similar molecular orientation. When LC molecules are oriented in a given direction, we can obtain a monodomain. One of the most used configurations in electrical devices with liquid crystals are planar cells. These cells are characterized by the fact that the molecules are anchored tangentially to the walls. By using transparent electrodes adhered to the glass layers, an electric field can be applied orthogonally to the cell. For large enough applied voltage, in the case of positive (negative) dielectric anisotropic susceptibility, the molecules try to reorient parallel (orthogonal) to the applied field. For small voltages, the molecules are not reoriented due to the interaction induced by the surface anchored molecules. Only when the voltage exceeds a critical value, the molecular reorientation begins. This phenomenon is known as the Freedericksz transition. Indeed, this transition corresponds to an exchange Indeed, this transition corresponds to an exchange of balance between electrical and elastic force. Harnessing the light intensity is crucial to all optoelectronic and electronic devices based on liquid crystals and using the birefringence and molecular reorientation. The determination of the Fréedericksz transition voltage is fundamental for all technological applications.