Superfast thermal melting of solids under the action of femtosecond laser pulses

The homogeneous formation of nucleation centers (nucleation) is regarded as a mechanism for the superfast thermal melting, of solids under the action of femtosecond laser pulses. On the basis of classical nucleation theory, it is shown that, for a high degree of superheating of the solid, the melting process is determined to a greater extent by the time of heating of the crystal lattice as a result of electron-phonon interaction than by the nucleation kinetics. Thus, the melting process can be completed in the course of several picoseconds. On one hand, this time is less than the characteristic time of heterogeneous surface melting and, on the other hand, it is greater than the time for possible superfast nonthermal melting. Experimental data on the melting dynamics of tellurium, obtained by polarization microscopy with femtosecond time resolution, confirm that superfast thermal melting is possible. (C) 2004 Optical Society of America.