Parametric Bistable Resonance in the Four Wave Interaction in Molecular Systems

Nonlinear optical processes due to the interaction of the vibrational modes in crystals (molecules) with external fields are usually described in terms of the nonlinear polarization of the medium. This polarization can be expressed as the power series of the small vibrational amplitudes, which are generally dependent on the external field intensity. In the procedures most frequently used the polarization is expanded only to the first order. The vibrational amplitude of the mode resonantly coupled to the field is found as the solution of the equation of the driven and damped oscillator (e.g. CARS).