Abstract:
Generation of the sum and difference frequencies ωvis±2ωir as a result of coherent four-wave frequency mixing of quasiresonance (relative to vibrationai transitions) CO2 laser radiation and of visible radiation in the form of the second harmonic of a YAG:Nd laser was studied in media consisting of various molecules (SF6, BCl3, CF3Br, CF3I). The signal was very sensitive to tuning of the infrared radiation frequency relative to the Q branch of a two-photon vibrationai transition. A theoretical model was developed which ensured a good agreement with the experimental dependence of the intensity of the signal on the infrared radiation frequency in the case of gaseous CF3Br. It was predicted theoretically that the investigated process should cause a considerable narrowing of the Q branch of a two-photon transition compared with the usual thermal width.