Studies of low power and high power optical phase conjugation

Abstract

This dissertation investigates mechanisms associated with very low and high power optical phase conjugation. The first part is a study of low power wave-front reconstructions produced by the surface reshaping through spatially nonuniform thermal expansion of an absorbing epoxy resin with a pump power in milliwatt range. A simple thermodynamic model is used to compare with the experimental data. The feasibilities and the limitations of this process in general real-time holographic applications are discussed. The second part is a study of high power OPC with a speckled pump beam in megawatt range. The experimental results show that self-focusing occurs at the onset of stimulated backscattering for focused speckled pump beams in CS$\sb2$. This implies a cooperative self-focusing effect within the speckled field. At regions beyond saturation, the compressibility of a liquid is limiting effect rather than beam depletion. A theoretical model which incorporates the nonlinear compressibility of a liquid at saturation region is developed. This theoretical model is in good agreement with the experimental data. Whereas Zel'dovich's theoretical model, which only includes the effect of pump depletion, predicts a result which is in an order of magnitude higher than the experimental measurements at regions beyond saturation.