Diagonal scan measurement of Cr:LiSAF 20 ps ablation threshold.

We report the measurement of the 20 ps ablation threshold of pure and Cr(3+) doped LiSAF samples using a simple method that employs a single scan of the sample across a focused laser beam waist. During the scan, a profile is etched in the sample surface, and the measurement of the maximum transversal size of the profile and the pulse peak power determine the ablation threshold, without any further knowledge of the beam geometry. Also, it was possible to measure the depth of the ablation profile, to calculate its effective volume, and to identify that the maximum material removal rate per pulse does not occur at the beam waist, which is not intuitively expected.