Abstract. The laser damage threshold for the onset of surface melting is measured. The dynamics and evolution of surface morphology are observed for different pulse power densities and number of laser pulses. With the power density increase, a sputtering phenomenon in the radial direction towards the periphery of the ablated zone is observed. The accumulation effect of heat due to pulses successively bombarding the surface is also evident. The damage threshold value calculated by the thermal model is in good agreement with the measured data in our experiment. As for the morphological changes, the thermal pressure model and shock pressure model can give a reasonable explanation. The periodic structure of ripples on the surface can be explained well by transverse surface acoustic wave theory.

Keywords: laser melting damage threshold, the mechanism of morphological changes, periodic structure

Print publication: Issue 1 (January 2006)
Received 16 July 2005, accepted for publication 15 November 2005
Published 22 December 2005