Spatial Solitons Due To Photorefraction Effect In Nematic Liquid Crystals

The spatial optical solitons in nematic liquid crystal refer to the non-diffracting optical beams. Solitons in nematic liquid crystal can interact in long distance, for the strong nonlocal nonlinearity and nonlinear saturation of refractive index of this material, for which the all-optical control can be studied in a new case. In this dissertation, the optical solitons induced by the light-induced index redistribution (photorefraction) in nematic liquid crystal are observed systematically in experiments, and the theoretical explains on the phenomenon are presented.At first, the research findings on this field are introduced and analyzed. The photorefraction effect in nematic liquid crystal, which is the mechanism of nonlocal solitons'generating progress, is discussed.Using the band transporting equations, we conceive the formation of the spatial electric field in nematic liquid crystal. Through minimizing the total free energy, and using the Helmholtz equation, we get the nonlocal nonlinear Schr?dinger equation of nonlocal optical solitons, originating from photorefraction effect in undoped nematic liquid crystals applied dc bias-voltage. And we numerically simulated the solitary solution and interaction between two solitons.The satisfactory liquid crystal cells are prepared. And we design the experiment layout independently, select appropriate experiment parameters, and observed the formation of the optical spatial solitons.We particularly discussed those factors influencing the formation of solitons in experiment, by setting different conditions, including power, polarization, wavelength of input beam, voltage applied on liquid crystal cells, thickness of cells etc.