Effect of the Molecular Interaction Between Anisotropic Molecules on the Optical Kerr Effect. Field-Induced Phase Transition

Abstract

The effect of molecular interaction between anisotropic (prolate) molecules in liquids on the nonlinear refractive index is studied. The model, without the driving term describing the strong optical-field molecular reorientation, is the same as the Maier and Saupe model of the isotropic to nematic phase transition in liquid crystals. The local field corrections are analyzed with the Onsager theory, the average polarizability being given by the Lorentz-Lorenz formula. It is found that the temperature dependence of the nonlinearity is modified and becomes ${(T-T_i)}^{-1\mathrm{}}$ and that the electric field required to achieve a certain nonlinear index change can be very much smaller than required when only molecular reorientation is considered. Under certain restrictive conditions the liquid can be driven into a new ordered phase, similar to a liquid-crystal mesophase.