Coupled-mode approach to the nonlinear dynamics induced by an elliptically polarized laser field in liquid crystals at normal incidence.

A coupled-mode theory is presented to describe the dynamics of the molecular director induced by an elliptically polarized light plane wave normally incident onto a homeotropic liquid crystal film. The model provides a set of time ordinary differential equations for the lowest two modes of the system while the influence of the higher-order twist modes is accounted for by means of the adiabatic approximation. The resulting dynamics is complex above the reorientation threshold, according to the intensity and polarization of the incident light, rotating, oscillating, or steady states may settle. The dynamical regimes have been studied as functions of external parameters. The agreement with the experimental data was very good.