PHASE DYNAMICS IN BISTABLE AND CHAOTIC BEHAVIOR OF A SOFT CRYSTAL MODE PARAMETRICALLY DRIVEN BY AN OPTICAL-FIELD

The dynamic behaviour of the amplitude and phase of the overtone of lo w-frequency lattice mode, generated in a crystal by a biharmonic optic al field via parametric process, is investigated theoretically. For de incident field amplitudes the vibrational amplitude undergoes strong bistable resonant enhancement, whereas it exhibits period doubling tra nsition to chaos when the field amplitude is slowly periodically modul ated. The evolution of the material system is shown to manifest itself in the similar features of the intensity of the optical field generat ed in the crystal in four-wave-mixing process.