Femtosecond three‐colour CARS of liquids with magic polarization conditions

It was shown recently that three scattering mechanisms with different time behaviours can be separated in time‐domain CARS simply by varying the polarization of the detected anti‐Stokes signal. In an extension of this work, the magic angle 49.1° for the elimination of the resonant‐anisotropic contribution was verified experimentally. It was also found that the residual non‐resonant scattering component observed at −60° with suppression of the common CARS interaction represents a six‐wave mixing process involving the optical Kerr effect. Using the novel polarization techniques the vibrational dynamics of neat dimethyl sulphoxide was studied in the CH stretching region. Evidence is reported for homogeneous broadening of the symmetric mode at 2913 cm −1 and for a doublet splitting of the asymmetric Raman band of the liquid at 2996 cm −1 not resolved in spontaneous Raman spectroscopy.