Dynamic gratings and the associated self diffractions and wavefront conjugation processes in nematic liquid crystals

The origins and the dynamics of optical nonlinearities in nematic liquid crystal films, namely, laser-induced molecular reorientational and thermal refractive index changes, are analyzed in the context of optical wave mixings. Theoretical expressions for the basic non-linearities, the rise and decay time, diffraction efficiencies, and other pertinent parameters involved in the dynamic grating formation are derived. Experimental results obtained with visible and infrared laser pulses are analyzed. Some newly observed novel nonlinear processes are also reported.