Femtosecond investigation of the non-instantaneous third-order nonlinear suceptibility in liquids and glasses

The symmetry of the noninstantaneous Kerr susceptibility is investigated in different liquids and glasses using a time-resolved two-beam energy transfer technique with pulses in the 100-15 fs range. The pulse duration dependence of the ratio of the isotropic chi(xxxx)((3)) to anisotropic chi(xyyx)((3)) tensor elements is demonstrated in liquid CS2 and in silica, showing that the elementary mechanisms mediating the observed optical beam energy transfers are modified for short pulses. This effect is ascribed to alteration of the nuclear contribution and increasing influence of the electronic one. (c) 2005 American Institute of Physics.