Investigation of distortion and damage of molybdenum-silicon multilayer reflective coatings with high-intensity ultraviolet radiation

Studies are performed to determine an upper limit on the optical damage threshold of a soft-x-ray molybdenum-silicon multilayer reflective coating by the use of a 308-nm, 15-ns pulse from a Xe-Cl excimer laser in order to simulate the potential damage induced by the x-ray flux from a pulsed laser-produced plasma. Experimental results yield a value of 0.26 J/cm² to produce visible signs of damage as determined by optical microscopy. Experiments are conducted first on silicon, as a reference point of a bulk material, and then applied to molybdenum-silicon in an effort to facilitate a theoretical comparison between a simple and a more complicated material. Theoretical predictions are in reasonable agreement with experimental results, but suggest that a lower value of 0.085 J/cm² might cause significant thermal-induced damage.