Interferometric diagnostic of picosecond laser ablation in air

Investigations of a spatial density distribution at the focus of an intense picosecond Nd:YAG laser pulse ls1064 nm. near a metallic target in air have been performed by interferometry and absorption photography with high temporal and spatial resolution 50 ps, -1 mm.. An effect of microchanneling and an intense shock-wave formation in laser-produced plasma were observed. Estimations show that the current density in the microchannel is of the order of 1010 Arcm2, followed by the generation of a self-magnetic field in the narrow channel having a magnitude of 7 MG. When the power density of laser radiation was reduced to a value of the order of 9=109 Wrcm2 a significant change in electron density distribution has been estimated: a shock wave with a strong boundary front vanished, an electron density failed under the value of the order of 1018 cmy3. q1998 Elsevier Science B.V.