From Bulk Janossy Effect to Nonlinear Self Wave-Guiding or Spatial Solution in Dye-Doped Liquid Crystals

The pure liquid crystalline state of matter is known for its large optical nonlinearity. The effect has been widely studied in thin film as the beam crosses it. Few studies have been done for a geometry in which the light interacts with the matter on a large volume. In this paper, we report the results we have obtained in this configuration (Bulk Optical Freederisckz Effect) and for dye-doped liquid crystals. In such mixtures, the nonlinear effect occurs at low input powers and is called the Janossy effect. Besides similar behaviors which occur in the Bulk Freederisckz Effect, it is reported in this paper a beam behavior, namely a self wave-guiding or "spatial soliton," which is probably more specific to the bulk Janossy Effect. This self created wave-guide is assigned to be a consequence of the dye absorption: the optically induced refractive index gradient is finely tuned by the additional anisotropic thermal contribution, allowing a quasi perfect optical coupling of the fiber source with the optically induced liquid crystal wave-guide.