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Laser damage testing according to ISO 11254 was performed with an automatic testing facility. With a Qswitch Nd:YAG laser up to 700 single "1 on I " tests were performed for each measurement. A detailed description of the experimental setup is given. Damage was on-line detected by light scatter measurements. Associated problems to this method are discussed here. To evaluate the energy-depended damage frequency values from the measured data, a reliable procedure is needed; different methods are tested. For the linear extrapolation of the damage frequency values to 0% damage frequency, as prescribed by ISO, a certain selection of data points is necessary. We discuss different types of damage statistics and the problems occurring using linear extrapolation.

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JB is now with Leybold AG, JunkersstraBe 1, D-8755 Alzenau (ERG)) ABSTRACF ISO-DIS 11254 specifies a test method for determining the laser radiation induced damage threshold of optical surfaces. It has been the intention to provide a method for obtaining consistent measurement results, which may be rapidly and accurately compared between different testing laboratories. Measurements according to ISO-DIS 11254 were performed with a Nd:YAG -laserwith 15 ns pulse duration. 544 test sites are included in the determination of the damage probability in dependence of the power density. An extrapolation of the damage probability to zero results in the damage threshold. Critical parts of the experimental set-up like beam diagnostics, beam attenuation and damage detection are considered in detail. Some shortcomings of the specified testing procedure are discussed on the basis of selected examples.

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