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14 July 1995 Removal of dust particles from metal-mirror surfaces by excimer-laser radiation
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The effect of particle desorption from Al mirror surfaces by the influence of pulsed UV laser radiation has been studied. The investigations are closely related to the demands of astronomers, who are looking for a more effective way of cleaning the Al coatings of future very large telescope mirrors. A systematic parameter study has been performed in order to determine the irradiation conditions which yield the highest dust removal efficiency (i.e. reflectivity increase) on contaminated samples, taking particularly into account laser-induced damage and degradation effects of coating and substrate. The particle removal rate increases with increasing laser fluence, being limited however by the damage threshold of the coating. Therefore, parameters influencing the damage threshold of metal coatings like wavelength, pulse width, and number of pulses have been studied in detail. Data indicate that on Al coated BK7 and Zerodur samples KrF laser radiation yields the optimum result, with cleaning efficiencies comparable to polymer film stripping. The initial reflectivity of the clean coating can nearly be reinstalled, in particular when an additional solvent film on the sample surface is applied. Hence, laser desorption seems to be a viable method of cleaning large Al mirrors for telescopes.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Klaus R. Mann, B. Wolff-Rottke, and F. Mueller "Removal of dust particles from metal-mirror surfaces by excimer-laser radiation", Proc. SPIE 2428, Laser-Induced Damage in Optical Materials: 1994, (14 July 1995);


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