Photoacoustic studies of excimer laser induced ablation of polymethylmethacrylate

Abstract

The ablation of polymethylmethacrylate (PMMA) at both 248 and 193 nm has been studied using photoacoustic techniques. The acoustic responses of PMMA during the ablation process are resolved into a bipolar, thermal component, and a unipolar, ablative component. This latter component is correlated to the center-of-mass velocity of the ablated material. Fluence-dependent studies show that the fragment center-of-mass velocity increases with increasing fluence even after the etch rate has reached saturation. In addition, results are presented suggesting that an increase in the absorption of the laser radiation by the fragments occurs at fluences above ∼4 J/cm2 causing a change in the profile of the ablated area.