Mechanistic studies of resonant infrared laser ablation of polystyrene

We investigate the phenomenon of resonant-infrared laser ablation of polymers using polystyrene as a model material. Ablation is initiated by a picosecond free-electron laser tuned to various infrared wavelengths that are resonant with vibrational modes of a polystyrene target. Time-resolved plume imaging, coupled with etch-depth measurements and finite-element calculations of the temperature rise indicate that ablation begins after a superheated surface layer reaches a temperature of nearly 1000C and undergoes spinodal decomposition. The majority of the ablated material is then expelled by recoil-induced ejection as the pressure of the expanding vapor plume compresses the laser-melted volume.