PULSED PHOTOACOUSTIC APPLIED TO DETERMINATION OF LASER ABLATION THRESHOLD ON METALS

The laser ablation thresholds of the copper, gold and silver metals were determined for the laser radiation of 1064 nm of a nanosecond Nd:YAG laser using the pulsed photoacoustic technique to record the photoacoustic signals produced due to the interaction of the metal with the laser pulses. These signals were analyzed using the standard correlation and changes in the photoacoustic amplitude as the laser fluence increased. The results indicate that the photoacoustic signals are very sensitive to physical changes that a solid sample experiences due to the interaction with laser pulses, being able to clearly differentiate the change from the thermoelastic to the ablation regime and consequently the ablation threshold. The values obtained for the threshold fluence were: (1.71 +/- 0.08) J/cm(2) for copper, (1.65 +/- 0.09) J/cm(2) for gold and (1.15 +/- 0.05) J/cm(2) for silver.