Thermodynamic evolution of phase explosion during high-power nanosecond laser ablation

It is argued that phase explosion plays an important role during high-power laser ablation. A theoretical model which includes the effect of an expanding mass plasma has been developed to describe the process of phase explosion during the interactions of a high-power nanosecond laser pulse on an aluminum target. For a laser with a 3-ns pulse duration, if the laser intensity is high enough (>or=5 x 10(10) W/cm(2)), phase explosion was found to occur after the completion of the laser pulse, but not during the process of laser energy deposition. This result is consistent with recent experiments. It is also found that the pressure of the induced ablation plasma plays a crucial role in the process of phase explosion.