Investigation of the plasma bursting process in short pulsed laser induced film damage

Abstract

Investigations on the interaction of short pulsed laser with optical films usually terminate at the ejection of film material. The plasma bursting process will happen, because the superhot ejection will absorb the remainder of laser energy. A two-steps numerical method has been used to deal with this process. In every computation time-step, two phases are used: the first one is the adiabatic expansion and cracking phase; the second one is the phase of absorbing laser energy. By this method, the energy absorption process and the bursting process are effectively coupled. For the thermodynamic parameters of the plasma micro-droplet, such as the radius, expansion speed and acceleration cracking speed and acceleration, densities and temperatures of electronic and ionic systems have been investigated. The results revealed that: the ejection will be atomized to micro-droplets in the early stage, and expansion dominates the latter part. The cracking velocity is cyclic, and the expansion velocity increases all the while. In specific cases, the expansion process may keep a dynamic stable state after the atomization. But it is difficult for this dynamic stable state to form.