Optical tuning of nonlinear dynamics induced by light in nematic liquid crystals

We study optical control of the nonlinear dynamics generated by an ordinary polarized light at a small angle of incidence in a nematic liquid crystal film. Recent experiments have demonstrated the possibility of modifying the molecular reorientation dynamics by the addition of a weak incoherent beam orthogonally polarized to the pump beam. We present a theoretical model for the director dynamics and we demonstrate the possibility to tune the complexity of the dynamics (optical tuning) using the weak beam intensity as a control parameter. The generation of new dynamical regimes, not observed in the single beam geometry, is also predicted. Finally, interpretation of optical tuning effects is discussed on the basis of an effective model.