Chemical precursor to optical damage detected by laser ionization mass spectrometry

Mass spectrometry was used in conjunction with Nomarski microscopy to characterize the initiation of optical damage in selected commercial optics. The reflective optics (351 nm) consisted of Sc2O3/SiO2 multilayer coatings on 7940 (glass) substrates. These samples were exposed to loosely focused 1.06 μm, 10 ns pulses at 10 Hz. At fluences above 100 mJ/cm2, transient iron signals were observed at each increasing fluence level, with concomitant appearance of small circular (10 μm) pits in the surface. The latter was observed by Nomarski microscopy. These small pits were also associated with macroscopic damage features resulting from threshold damage testing.