Difference of spectral superbroadening behavior in Kerr-type and non-Kerr-type liquids pumped with ultrashort laser pulses

The spectral superbroadening behavior of forward coherent radiation from a 10-cm-long liquid-filled cell is investigated by using an ultrashort (∼0.5 ps) and intense (∼10 GW/cm(2)) laser pulse as the pump source. Five different transparent liquids (heavy water, water, carbon tetrachloride, benzene, and carbon disulfide) have been studied with a special experimental design that can distinguish the predominant contributions from the various possible mechanisms. Under the same pump condition, a very wide and symmetrical superbroadening (continuum) is observed on both the Stokes and the anti-Stokes side of the pump line for non-Kerr-type liquids such as heavy water and water, whereas only a red-shifted spectral broadening can be observed on the Stokes side for Kerr-type liquids such as carbon disulfide and benzene. For an explanation of the latter behavior, the dominant contributions from stimulated Rayleigh-Kerr and Raman-Kerr scattering are proposed.