Experimental study of the transmission of breakdown plasma generated during laser shock processing

Shock wave generation from laser-produced plasma in water confinement regime for an incident 25-30 ns / 40 J / lambda = 1.064 mu m laser beam has been studied. Transmitivity measurement of the parasitic plasma breakdown at the surface of water confinement has been performed with a continuous laser probe. Above 6 GW/cm(2) incident laser intensity, the critical electronic density for the laser wavelength is achieved inside the plasma by cascade ionization during the pulse duration. Above 10 GW/cm(2), peak power density transmitted through the plasma saturates. The laser pulse transmitted through the breakdown plasma corresponds to the part of incident laser pulse preceding the transmission cut-off.