Interaction of CO2 laser nanosecond pulse train with the metallic targets in optical breakdown regime

Abstract

Many phenomena accompaning the air optical breakdown (in particular the electric fields and currents arising in breakdown plasma) sufficiently depend on the temporal parameters of laser radiation. For example, utilization of two successive laser pulses results in considerable increase of the magnetic fields and currents. In the present chapter, the electric fields and currents in the air breakdown plasma produced by a train of CO2 laser nanosecond pulses near the surface of uncharged metallic targets were studied. The breakdown thresholds as well as efficiency of plasma-target heat transmission for different temporal parameters of CO2 laser radiation were measured. Regenerative amplification (RA) enables transformation of free running mode laser pulses into the train of nanosecond ones with varied duration of the individual pulse and time interval between the pulses. For this reason, we have used RA for carrying out the experiments. The numerical calculations made it possible to predict the influence of RA scheme parameters upon the temporal structure of the nanosecond pulse train and thus facilitate realization of the experimental set up.