PHASE-CONJUGATE REFLECTION BY DEGENERATE 4-WAVE-MIXING IN 2-(2'-HYDROXYPHENYL)BENZIMIDAZOLE DYE SOLUTIONS - SOLVENT EFFECTS

Thermally induced phase conjugation by degenerate four-wave mixing in solutions of the proton-transfer dye 2-(2'-hydroxyphenyl)benzimidazole in methanol, acetonitrile, 1,4-dioxane, and N,N-dimethylformamide in the weak absorption region, low-reflectivity regime, and nanosecond ti me domain is reported. Evidence of oscillatory acoustic modes in the n on-linear medium is presented and existing theories are shown to expla in satisfactorily the experimental results. Several aspects of the the rmally induced phase conjugation process have been explored, with emph asis on the effect in the process efficiency of variables such as dye concentration, fluorescence quantum yield, and read beam time delay. T he fast processes leading to the formation of the electronically excit ed tautomer seem To be the main contributors to the formation of therm al grating in the studied media.