POLARIZATION INTERFERENCE IN FEMTOSECOND CARS

The polarization properties of three-colour coherent Raman spectroscopy are investigated theoretically and experimentally; it is shown that three scattering contributions with different polarization behaviour occur via the nonresonant, resonant isotropic and resonant anisotropic parts of the third order nonlinear susceptibility. Proper choice of the polarization geometry allows to adjust destructive interference; i.e. magic angles with elimination of individual scattering components. Perturbation via the optical Kerr effect of the input pulses is discussed. More than three orders of magnitude of suppression are measured for the nonresonant CARS signal (example CCl4) while a suppression factor of 10(4) is achieved for the isotropic signal contribution (example acetone). The potential to study the molecular reorientational relaxation is demonstrated.