The mechanism of ablation of solids by intense femtosecond laser pulses isdescribed in an explicit analytical form. It is shown that at high intensitieswhen the ionization of the target material is complete before the end of thepulse, the ablation mechanism is the same for both metals and dielectrics. Thephysics of this new ablation regime involves ion acceleration in theelectrostatic field caused by charge separation created by energetic electronsescaping from the target. The formulae for ablation thresholds and ablationrates for metals and dielectrics, combining the laser and target parameters,are derived and compared to experimental data. The calculated dependence of theablation thresholds on the pulse duration is in agreement with the experimentaldata in a femtosecond range, and it is linked to the dependence for nanosecondpulses.
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