INFLUENCE OF THE LASER-SPOT DIAMETER ON PHOTOABLATION RATES

The dependence of the ablation rate of various materials on the laser spot diameter on the sample surface has been investigated. The experim ents have been performed with excimer lasers at the wavelengths 193, 2 48 and 308 nm. Polymers, aluminum oxide ceramics and glasses have been ablated under vacuum and ambient atmosphere conditions. In general, a ll materials show a more or less pronounced increase of the ablation r ate with decreasing spot diameter in the range of 10-200 mu m if pulse s with nanosecond pulse durations are applied. For ultrashort pulses ( 500 fs) at 248 nm this diameter dependence is not observed. The expans ion of the ablation plume over areas of different size seems to be the main reason for this effect.