Phase conjugation in methyl orange doped polyvinyl alcohol film by DFWM based on excited state absorption

Abstract

The kinetic process of degenerate four-wave mixing (DFWM) based on excited state absorption is studied for the first time. A four-level model of two singlet states and two triplet states was used to explain the DFWM. The lower triplet state could be significantly populated through intersystem crossing between an excited singlet state and the triplet state, therefore the degenerate four-wave mixing based on triplet-triplet absorption was achieved. The phase conjugation signal in the DFWM process was modulated by the preexciting intensity. A typical experiment was performed, in which methyl orange doped in polyvinyl alcohol film was used as the experimental sample, an argon ion laser at 514.5 nm was used as the preexciting field, and a HeNe laser at 632.8 nm was used as the DFWM source. The experimental and calculated results were in good agreement.