TRANSIENT GRATING OPTICAL HETERODYNE DETECTED IMPULSIVE STIMULATED RAMAN-SCATTERING IN SIMPLE LIQUIDS

The real and imaginary parts of individual tenser elements of the nonr esonant third-order nonlinear optical susceptibility of simple liquids , carbon tetrachloride and benzene, have been characterized for the fi rst time by transient grating optical heterodyne detected impulsive st imulated Raman scattering (TG-OHD-ISRS). Optical heterodyning is achie ved through additional scattering induced by a thermal grating. Vibrat ional modes to 1000 cm(-1) are impulsively prepared and probed using 1 5 fs laser pulses. This technique allows for a precise determination o f frequencies and dephasing times of intramolecular Raman-active vibra tions. It is shown that the symmetry of these modes defines the measur ed phase of the oscillatory modulations of the various linearly detect ed tenser components of chi((3))(t). Advantages to conventional techni ques, such as optical heterodyne detected Raman induced Kerr effect sp ectroscopy or homodyne detected impulsive stimulated Raman scattering, are demonstrated. Further detection of the real or imaginary part of the susceptibilities using phase locked femtosecond optical pulses is discussed.