Interferometric investigation of optical breakdown in air at the surface of a metallic target

An investigation was made of the thermal processes which accompany optical breakdown in air at the surface of a metallic target. A titanium target was subjected to radiation of power density $\thicksim0,3$ MW/cm${}^2$ from a $CO_2$ gas-discharge laser, for a period of $\thicksim1$ msec. The use of interferometric diagnostics having adequate spatial and temporal resolution ($\thicksim300\mu m$ and $\thicksim30\mu s$) made it possible to describe the heating of the air at the target surface before breakdown, the formation and propagation of the breakdown plasma, the absorption of laser radiation in it, and the heating of the air by the plasma. Estimates were made of the plasma parameters.