Laser swelling model for polymers irradiated by nanosecond pulses

Mechanisms of laser swelling of polymers are considered. A theoretical model for one of such mechanisms is constructed and investigated. This mechanism is based on the formation of a thermoelastic wave upon absorption of a laser pulse. Tensile stresses in this wave lead to elastic and plastic deformation of a polymer in the heated region and to the formation of convex structures (humps). The threshold fluence of a laser pulse required for the production of a residual hump under laser irradiation is obtained analytically. A formula for the height of this hump is also derived. The model explains the earlier experimental data from the literature on swelling of a PMMA film irradiated by UV pulses.