Effect of excited singlet states of molecules on the efficiency of four-wave interaction in dye solutions

Abstract

This paper studies the characteristics of wave-front reversal with FWI in dye solutions modeled by a three-level scheme. The model takes into account the transitions between the excited singlet states 2-3 and can be used to describe the dye when the triplet states can be ignored. Presented are the results of a numerical analysis of the effect of the excited singlet levels on the energy efficiency of the WFR under the assumption that the Einstein coefficients B/sub 12/, B/sub 21/, B/sub 23/, B/sub 32/ at the maxima of the Gaussian contours are equal. It is determined that when pumping intensity is increased, the heating of the dye solution by means of thermalization of the energy by transitions between the excited states of molecules has a significant effect on the energy efficiency of reflection of the reversed wave. A decrease in the quantum yield of luminescence leads to an increase in the amplitude of the thermal gratings and therefore to an even larger effect of the thermal nonlinearity on the energy efficiency of reflection in the region of the second maximum.