Near-Surface Plasma Formation in Air with Exposure to Dual Laser Pulses at Two Wavelengths.

We have experimentally studied the spectra and structure of a near-surface plasma and measured the recoil impulses when brass and graphite targets are exposed in air to dual laser pulses at the wavelengths 0.532 μm and 1.065 μm, as a function of the time interval between the laser pulses and the pulse sequence. We have established the dependences of the temperature of the laser plasma and the concentration of charged particles and also the recoil impulse on the parameters of the dual laser pulses for laser power density 4·109 W/cm. We show that the optimal conditions for recording the spectra of the ablation plasma occur when the second-harmonic radiation arrives first with time interval between laser pulses of 1.5-6 μs, and the optimal conditions for generating the recoil impulse involve an interval of 1.5-2 μs, which is important for improving the performance of emission laser spectral analysis and laser plasma micromotors for aerospace applications. [ABSTRACT FROM AUTHOR]