Degenerate four-wave mixing in phenylbenzimidazole proton-transfer laser dyes

Thermally induced phase conjugation by degenerate four-wave mixing in 1,4-dioxane solutions of the 5′-fluoro and 5′-chloro derivatives of the 2-(2′-hydroxyphenyl) benzimidazole proton-transfer dye is reported in the weak absorption region, low-reflectivity regime and nanosecond time domain. Efficiency-related aspects of the nonlinear process are investigated and the different contributions to the thermalization processes are discussed. Evidence of oscillatory acoustic modes in the nonlinear medium is presented.