Investigation of optical damage via resonance ionization mass spectrometry

Resonance ionization mass spectrometry (RIMS) has been used as a diagnostic for interrogating optical damage events. RIMS involves multistep laser photoionization, generally through real intermediate states, followed by mass separation and detection. It is a sensitive and selective means of detection, and has the potential for detection of ultratrace inclusions in substrates and/or coatings. In initial experiments, damage on uncoated CaF2 substrates was initiated by pulses of 1.06-(MU)m light from a Q-switched ND(+3):YAG laser. Interrogation of the spalled plume revealed CaF radicals only when damage events occurred. No Ca atoms were observed, and no attempt was made to detect F atoms or CaF2. In subsequent experiments conducted at laser intensities below the damage threshold, we observed the presence of surface adsorbents and a correlation between the presence of the adsorbents and the occurrence of optical damage.