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

摘要

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 χ_(xxxx)~((3)) to anisotropic χ_(xyyx)~((3)) tensor elements is demonstrated in liquid CS_2 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.