Phase-conjugate reflection by degenerate four-wave mixing in 2-(2′-hydroxyphenyl)benzimidazole dye solutions: solvent effects Original Research Article

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 time domain is reported. Evidence of oscillatory acoustic modes in the non-linear medium is presented and existing theories are shown to explain satisfactorily the experimental results. Several aspects of the thermally induced phase conjugation process have been explored, with emphasis on the effect in the process efficiency of variables such as dye concentration, fluorescence quantum yield, and read beam time delay. The fast processes leading to the formation of the electronically excited tautomer seem to be the main contributors to the formation of thermal grating in the studied media.