From bulk Janossy effect to nonlinear self wave-guiding or spatial solitonin 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 c rosses it. Few studies have been done for a geometry in which the light int eracts with the matter on a large volume. In this paper, we report the resu lts we have obtained in this configuration (Bulk Optical Freederisckz Effec t) and for dye-doped liquid crystals. In such mixtures, the nonlinear effec t occurs at low input powers and is called the Janossy effect. Besides simi lar behaviors which occur in the Bulk Freederisckz Effect, it is reported i n this paper a beam behavior, namely a self wave-guiding or "spatial solito n," which is probably more specific to the bulk Janossy Effect. This self c reated wave-guide is assigned to be a consequence of the dye absorption: th e optically induced refractive index gradient is finely tuned by the additi onal anisotropic thermal contribution, allowing a quasi perfect optical cou pling of the fiber source with the optically induced liquid crystal wave-gu ide.