Superbroadening inH2O andD2O by self-focused picosecond pulses from a YAlG: Nd laser

The dielectric breakdown intensity threshold, the critical power for self-focusing, and the power threshold for the production of spectral superbroadening have been measured in ${\mathrm{H}}_2$O and ${\mathrm{D}}_2$O. For bandwidth limited pulses of 30 psec duration at 1.06 μm, and 21 psec duration at 0.53 μm, the superbroadening in water always required power levels sufficient for catastrophic self-focusing and intensities equal to the electric breakdown threshold.