Nematic liquid crystal cells for optical spatial solitons (Nematicons)

The study of optical solitons and light filaments steering in liquid crystals requires utilization of particular cells designed for top view investigation and realized with an input interface which enables both to control the molecular director configuration and to prevent light scattering. Up to now, the director orientation imposed by this additional interface has been only estimated by experimental observations. In this paper, we report on the design and characterization of liquid crystal cells for investigation of optical spatial solitons as well as on a simple model describing the configuration of the molecular director orientation under the anchoring action of multiple interfaces. The model is based on the elastic continuum theory and only strong anchoring is considered for boundary conditions. Controlling of the director orientation at the input interface, as well as in the bulk, allows to obtain configurations that can produce distinct optical phenomena in a light beam propagating inside the cell. For a particular director configuration, it is possible to produce two waves: the extraordinary and the ordinary one. With a different director configuration, the extraordinary wave only is obtained, which propagates inside the cell at an angle of more than 7 degrees with respect to the impinging wave vector direction. Under this peculiar configuration and by applying an external voltage, it is possible to have a good control of the propagation direction of the optical spatial soliton.