2ND-HARMONIC GENERATION OF A PICOSECOND LASER-PULSE AT HIGH INTENSITIES WITH TIME PREDELAY

We describe an experiment on second-harmonic generation of a picosecon d laser pulse with time predelay at intensities of up to 200 GVV/cm(2) . Duration of the second-harmonic pulse was reduced to 0.6 ps from the 1.5 ps width of the fundamental pulse at an optimum intensity of 50 G W/cm(2). The spatial profile of the laser beam is not degraded by self -focusing at an input intensity of near 50 GW/cm(2).