Numerical Study of the Dynamics of Gold Heating by Ultra-Short Dichromatic Laser Pulses

The interaction of femtosecond laser pulses of moderate intensity with metals by the example of gold is studied. The main attention is paid to dichromatic regimes of laser irradiation corresponding to a new trend in the field of laser pro-cessing of materials. Based on the two-temperature approximation, a new model is created which involves a dichro-matic source of the laser radiation energy and also takes into account the influence of the electron temperature on the reflection coefficient of the irradiated material and thermophysical properties of its electronic subsystem. For numerical implementation of the model, an implicit divergent finite-difference scheme is created with an improved method for describing the melting process in comparison with previous works. The model calculations have shown that the absorption of the laser energy by gold depends on the sequence of two pulses at different wavelengths and the delay time between them, and for correct description of the absorbed energy, it is necessary to take into account the change of the reflection coefficient of the surface during irradiation. The developed model may be of interest for optimizing the processing of materials with ultra-short dichromatic laser pulses.