Investigation On Spatial Solitons And Soliton-Induced Waveguide In Methyl-Red Doped Nematic Liquid Crystals

The spatial optical solitons in liquid crystals refer to the non-diffracting optical beams propagating in nematic liquid crystals. By changing the time of recording or the incident intensity, permanent or instantaneous waveguides can be stored in the doped nematic liquid crystals; in addition, the permanent waveguides in the deeply doped samples can't be erased by uniform illumination, biased electromagnetic field or heating. As a result, the spatial optical solitons will be used widely and prospectively in optical information processing, integrated optics, optical bistability, optical storage, optical connection and optical computation. The dissertation focuses on the formation and evolution of spatial optical solitons in methyl-red doped nematic liquid crystals, which can be a foundation for actual application.At first, both abroad and domestic achievements in the field are analyzed and summarized. Starting from hydrodynamics, solid-state continuum theory and sets of Maxwell equations, the coupled equations of the spatial optical solitons in nematic liquid crystals are described theoretically, then the general theory of dynamics of spatial solitons in doped nematic liquid crystal (strong nonlocal nonlinear) are introduced, which is profound and meaningful.By making appropriate planar liquid crystal cells, using the semiconductor laser as the incident source and the He-Ne laser as the detecting light source, planning and building optical experimental facilities independently and attempting different experimental parameters, spatial optical solitons and their induced waveguides are finally observed in unbiased methyl-red doped nematic liquid crystals. By illuminating the cells for a longtime, permanently stored waveguides are formed in our experiment, which makes it possible to realize the large-scale storage, transmission and processing of information.The influence on the producing solitons and their induced waveguides of the factors such as the intensity of incident light, the state of polarization, the cells'thickness and the concentration of methyl-red are discussed separately. It's found in our experiment that the intensity of semiconductor laser decides whether the solitons and their induced waveguides can be formed in medium or not, while the intensity of He-Ne laser doesn't play the same role; under appropriate incident intensity, both the horizontally polarized light along x-axis and the vertically polarized light along y-axis can form spatial solitons and waveguides; when increase the cells'thickness, the intensity of semiconductor laser needed to produce solitons and waveguides reduces; the stronger of the methyl-red liquid, the more obvious phenomenon can be observed, and the longer distance that solitons can propagate. In addition, the formation of spatial solitons whose propagating distance is longer than 8mm has been observed in our experiment.In the end, spatial optical solitons formed in doped and pure liquid crystals are compared as far as the elements including incident intensity, polarization states, biased voltage and responding time.