Long-time radiation resistant optical coatings for UV excimer laser applications

An example of a multilayer components for 248nm excimer laser applications is explained in this contribution. By means of a polarising beam splitter the potential of plasma-assisted deposition is shown. Such a coating shows a high reflecting and a high transmitting function for different polarisation at a certain angle of incidence. High reflection requires a considerable number of layer pairs with a large total optical film thickness. Despite of large film thickness the optical absorption can be minimised and high transmission can be obtained. The laser induced damage threshold of such a coating is in the order of 2.5 J/cm(2) for single shot measurements at 20ns pulse length. The life time is > 5x10(9) shots at a fluence of 10mJ/cm(2). Very stable deposition conditions must be maintained to produce these coatings within small tolerance of the optical function. It was found that plasma-assisted deposition is a more reliable technology for producing these coatings compared to classical evaporation.