Stimulated orientational and thermal scatterings and self-starting opticalphase conjugation with nematic liquid crystals

A quantitative theory and experimental results on self-starting optical pha se conjugation, using stimulated orientational and thermal scattering in ne matic liquid crystal films, are presented. The coupled wave-material equati ons for the laser-induced refractive index changes, grating formation, and coherent wave mixing effects are developed. Analytical solutions are obtain ed for the case of negligible pump depletion, and numerical solutions for v arious input and generated signals, taking losses into account, are obtaine d. Experimentally, we demonstrate the feasibility of realizing these stimul ated scattering and phase conjugation processes in thin (200 mum) nematic l iquid crystal with a milliwatt-power cw laser. Theoretical estimates for va rious gain constants and threshold intensities, and their dependence on var ious physical parameters, are found to be in good agreement with experiment al observations.