Dynamic absorptance behavior of hybrid multilayers at 193 nm

Abstract

In previous years different multilayer systems were investigated with respect to their optical performance at the wavelength 193 nm of the ArF excimer laser. For most applications in this spectral range, fluoride coatings have been qualified and are widely established. Even though the applicability of oxide coatings is strongly restricted by the significant intrinsic absorptance of the Al203 component, these materials are utilised for special technology fields.In contrast to the dielectric deposition materials, the potentiality of protected and enhanced metal layer systems has not been investigated in detail as a basis for high reflectivity minors at the wavelength of 193 nm. The major advantage of metal layers is their relatively high reflectivity which can be achieved at low film thickness. Thus metal layers can be employed as a substitution of the first HL-pairs in a high reflecting dielectric stack, and the number of layers can be drastically reduced. Furthermore, the upper residual fluoride stack shields the metal coating from the E-field improving the power handling capability of the metal layer structure.The present investigations are focused on the determination of the absorptance in dependence on the different number of fluoride HL-pairs in metal/dielectric layer systems. In order to elucidate this loss channel, the laser calorimetric (LCA) method in accordance to ISO 1 1551 is employed. The dynamic behaviour of the absorptance is measured on the basis of the thermal lens technique (ii) using the obtained data of the LCA method for calibration. With regard to both experimental methods, the absorptance can be defined in a wide range of fluence values including the damage onset, and the laser induced damage behaviour of the coatings can be studied. keywords: laser calorimetry, thermal lens technique, ISO 1 1 55 1 , LIDT, predamage, UV dielectric coatings, enhanced metal coatings