Investigation of conical structures created by ArF excimer laser irradiation of polycarbonate

Conical structures develop on the surface of ArF excimer laser ablated polycarbonate between 20 and 600 mJ/cm2. The cause of this is that the particulate impurities (which are responsible for the formation of cones) are also removed above 600 mJ/cm2 and ablation of polycarbonate does not occur below 20 mJ/cm2. The dependence of the apex angle of the cones on the fluence is investigated. It is shown that the shape of the cones depends on the polarization of the UV beam. A simple computation is proposed to model the formation of the above-mentioned structure. This is in good agreement with the experimental results.