Efficient surface-erosion plasma formation in air due to the action of pulse-periodic laser radiation

A study was made of the interaction of a series of periodic laser (λ = 1.06 μm) pulses with a number of materials (aluminum, copper, graphite, ebonite) in air at laser radiation power densities q = 10⁷–10⁹ W/cm² and repetition frequencies f≤50 kHz. The radiation was concentrated in spots of ~ 10 ^– 2 cm² area. Efficient formation of plasma as a result of laser erosion (q > 2 X 10⁸ W/cm², f≥5 kHz) was observed. A screening layer of an air plasma created by the first pulse of the series was expelled from the interaction zone and this was followed by erosion plasma formation under conditions of slight screening of the target during the action of the subsequent laser pulses.