The characteristics of diffracted waves derived from four- and six-wave mixing in a solution of \nRhodamine 6G dye are studied in different combinations of the polarization states that participate in wave \ninteraction.
This work presents theoretical and experimental studies of the energy efficiency of multiwave mixing in complex molecular media (dye solutions) exhibiting higher order nonlinearities. There is a great variety of such media, including the resonance ones revealing nonlinearities of higher orders due to the absorption saturation effect and transitions between different excited states of the molecules. However, the majority of previous studies of multiwave mixing have been performed in the resonant medium approximation disregarding the induced anisotropy effect. A new method for enhancement of multiwave mixing in solutions of laser dyes has been proposed and substantiated with the use of lasing as an additional light beam, whose absorption by the molecules in the excited states leads to the formation of thermal dynamic gratings resultant in the improved efficiency of the energy exchange. The theoretical models for the formation of nonlinear dynamic holograms adequately describing the control process over multiwave mixing by an independent light beam, the frequency of which is tuned into the induced absorption band from the molecules in the excited state, have been developed. Polarization multiwave mixing has been realized in Rhodamine-6G dye solution using nonlinearities up to the ninth order inclusive. It has been demonstrated that on orthogonal polarization of the hologram recording waves the diffraction efficiency is lowered by one-two orders, the diffracted wave polarization being dependent on the diffraction order (the polarization plane alignment is identical within the orders of the same evenness).
In this work the different schemes of propagation and interaction of the light beams in nonlinear Fabry-Perot interferometer have been studied theoretically and experimentally. Degenerate and non-degenerate four-wave mixing have been realized in the cavity of Fabry-Perot type using Rhodamine-6G dye and polymethine dye 3274U solution as saturable absorber. The diffraction efficiency of intracavity dynamic grating has been studied in dependence on intensity of interacting beams and parameters of resonator. The theoretical model of the processes of intracavity degenerate and non-degenerate four-wave mixing has been developed and applied to the analysis of the efficiency of light beams conversion by mean of Bragg diffraction from intracavity dynamic gratings. For theoretical description of typical experimental situations we used the round-trip model of nonlinear interferometer adapted for the geometry of degenerate four-wave mixing, which can be realized in the scheme of symmetrical oblique incidence of pump, signal and probe beams to the front and back mirrors of cavity.