The intensity profile of a radially symmetric laser beam is shown to be invertible from knife-edge data via the inverse Abel transform of the first derivative of the data. Two numerical algorithms for inverting pulsed-beam data are applied to a knife-edge scan of the focused output of a confocal unstable resonator laser. The resulting beam profiles are shown to be in good agreement with each other but significantly different from the profile obtained by assuming the beam to be approximately Gaussian. The results are shown to predict that the laser damage threshold of polymethylmethacrylate is ~4 times as large as previously reported.
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