The standardization and the comparison of laser-damage testing are essential prerequisites for development and quality control of large optical components used in high-power laser facilities. To this end, the laser-induced–damage thresholds of two different coatings were measured at four laboratories involved in a round-robin experiment. Tests were conducted at 1 m in the subpicosecond range with different configurations in terms of polarization, angle of incidence, and environment (air versus vacuum). In this temporal regime, the damage threshold is known to be deterministic, i.e., the continuous probability distribution transitions from 0 to 1 over a very narrow fluence range. This in turn implies that the damage threshold can be measured very precisely. These traits enable direct comparison of damage-threshold measurements between different facilities, while the difference in the measured values are not accompanied by large statistical uncertainties.
In this presentation, the results of this comparative experiment are compiled, illustrating the challenges associated with accurately determining the damage threshold in the short-pulse regime. Specifically, the results of this this round-robin damage-testing effort exhibited significant differences between facilities. The factors to be taken into account when comparing the results obtained with different test facilities are discussed: temporal and spatial profiles, environment, damage detection, samples homogeneity and nonlinear beam propagation.