Reexamination of the theory and experimental results of optically induced molecular reorientation and nonlinear diffractions in nematic liquid crystals: Spatial frequency and temperature dependence

We present a detailed calculation of, and experimental results on, the dependence of degenerate four-wave mixing and nonlinear diffraction in a nematic film on the spatial frequency of the intensity grating generated by two overlapping lasers. The explicit analytical expressions allow a critical reexamination of previous results and lead to better agreement between theory and experiments. Some of the previous theoretical and experimental results are reconfirmed. We also present further detailed results on the temperature dependence of nonlinear diffraction.