Optical phase conjugation and efficient wave front correction of weak light beams by dye-doped liquid crystals

We report the observation of optical phase conjugation by thin nematic liquid crystal films by using submilliwatt incident power without any external applied field. The light-induced average birefringence evaluated by solving the wave equations for the four interacting waves, is in agreement with that typical of the colossal optical nonlinearity recently observed in the same materials. The high conjugated reflectivity values, obtained with the analyzed samples, allows correction of severely aberrated wave fronts of very weak light beams. (C) 2003 American Institute of Physics.