Influence on temporal and spatial intensity distribution on materials processing by excimer lasers

Presently available commercial excimer laser systems show variation of the beam power in time and space across the beam diameter. Depending on the position in the beam cross section with respect to the optical axis variations of local pulse energy (J/cm/sup 2/), local pulse power (W/cm/sup 2/), local pulse length (ns), and pulse shape have been recorded. The effect of such variations for general characteristics of materials processing by laser radiation is evident. For example, threshold phenomena such as ablation, surface melting, vaporization or laser-induced plasma formation depend on the laser intensity and time of irradiation sensitivity. Changes of intensity or time of only about 10% can result in the occurrence or absence of the mentioned phenomena. At the very least the influence of beam inhomogeneities on the homogeneity of the processing result has to be visualized. For example, processing characteristics and results of surface treatment in the cm/sup 2/ range are presented. The effect of intensity distribution variations on the result is shown in several examples. As criteria for characteristic processing the resulting surface structure and degree of oxidization have been chosen; as sample materials aluminum and copper were used