Influence of the beam spot size on ablation rates in pulsed‐laser processing

Ablation rates in pulsed‐laser processing depend heavily on the laser beam spot size. This has been observed for the first time for a number of different materials. Detailed investigations on this effect, performed by means of XeCl excimer‐laser radiation and the example of LiNbO3, are reported in this letter. With this material, the ablation rate at constant fluence saturates at laser beam spot sizes of 2w≳80 μm and increases by about a factor of 3 when 2w is decreased to 24 μm. The effect is interpreted as being due to changes in the material transport which depend on the size of the region being processed.