2ND-HARMONIC GENERATION OF AMPLIFIED FEMTOSECOND TI SAPPHIRE LASER-PULSES

We study theoretically and experimentally second-harmonic generation ( SHG) of 150-fs-duration amplified Ti:sapphire laser pulses at a wavele ngth of 780 nm in the nonlinear crystal KDP of different lengths and a t different power densities as high as 150 GW cm-2. The experimentally observed SHG conversion efficiency does not exceed 50%. It is shown t heoretically that one possible process limiting the SHG efficiency at low as well as at high intensities is the modulation of the phase of t he fundamental wave. In addition, continuum generation is observed at high intensities and can decrease the SHG efficiency.