Studies of self-phase modulation under cw and picosecond laser pumping: White light continuum generation in water

White light continuum generation (WLC) has been studied in water, D2O and their mixture under ps laser pumping. Its spectrum extends from 450 to 970 nm. Strong contributions from self-phase modulation (SPM) and stimulated Raman scattering (SRS) are observed. To study the spatial SPM and SRS separately from each other, the stimulated Raman scattering spectrum has been recorded for acetone by using the ps laser at 1064 nm while the effect of spatial SPM is demonstrated with a Gaussian profile of Ar ion laser in an organic dye. The high optical nonlinearity of the dye results in diffracted rings in the far field of the observed diffracted pattern. A comparison with the WLC obtained by fs pumping, has been given on the basis of the available data in the literature. © 2005 IACS.