OVERHEATED METASTABLE STATES IN PULSED-LASER ACTION ON CERAMICS

Volume overheating of solid and liquid phases in pulsed laser evaporation of superconducting ceramics is analyzed by numerical simulation. The mathematical model includes the processes of heating (with a volume energy release), melting-solidification, and evaporation. It is shown that the maximum values of overheating of the solid phase (with respect to its melting point) exceed 100 degrees and those of the liquid phase exceed several hundred degrees (with respect to the surface temperature). The times of existence of these metastable states are tens and hundreds of nanoseconds, respectively. The dynamics of the processes are analyzed in a wide range of variation of the absorption coefficient (i.e., laser wavelength). It is shown that the probability of explosive decay of the metastable states in the solid phase increases with laser wavelength, whereas for the metastable states in the liquid phase the overheating parameters exhibit a maximum versus laser wavelength. © 1995 American Institute of Physics.