Mechanisms of excimer laser ablation of strongly absorbing systems

Abstract

The absorption behavior of model polymeric systems is investigated in the low (< 50 mJ/cm2) and high (> 1 J/cm2) fluence regime at standard excimer laser ultraviolet wavelengths. The new technique of nanosecond time resolved thermometry is exploited to resolve the heating and cooling rate, as well as the total thermal load of a thin polymer film that is exposed to low fluence irradiation. The results suggest that a thermal model of heating and ablation is appropriate for these systems. This represents the first direct measurement of the time resolved heating of a strongly absorbing polymer system. In addition, a new nanosecond time resolved digital photographic technique has been used to image the shock wave and debris dynamics of a polymer undergoing high fluence ablation. These results suggest that, at high fluences, the total energy in the incident photon pulse can be entirely accounted for in the energy driving the shock wave.