The applicability of hydrodynamic models for theoretical
description of UV laser ablation of polymers is studied.
The plume formation is considered as a first-kind phase
transition. In case of strongly absorbing polymers this
phase transition occurs as a surface evaporation, and in
case of weakly absorbing polymers as a bulk evaporation.
The vapor plume is assumed to be transparent for laser
radiation, and its expansion is described by the isoentropic
hydrodynamic equations. New analytical expressions for
ablation (etch) depths per pulse are obtained, which are
in good agreement with the available experimental data
(Afanasiev et al. 1997).