E. Stenzel et al., LASER DAMAGE OF ALKALINE-EARTH FLUORIDES AT 248 NM AND THE INFLUENCE OF POLISHING GRADES, Applied surface science, 110, 1997, pp. 162-167
Citations number
21
Categorie Soggetti
Physics, Condensed Matter","Chemistry Physical","Materials Science, Coatings & Films
Damage behaviour and thresholds for single 248 nm/14 ns excimer laser
pulses have been investigated for single crystals of CaF2 and BaF2 wit
h (111) surface orientation. The probe beam deflection technique was a
pplied as a sensitive tool for detecting the onset of single-shot dama
ge. Below the plasma threshold, we observed one- and two-photon absorp
tion for CaF2 and BaF2, respectively, When testing the influence of di
fferent polishing techniques, we found the lowest thresholds for conve
ntional hard-polish. Advanced methods as ductile machining or chemical
polishing lead to a distinct increase in damage threshold up to and e
ven better than what is observed for cleaved surfaces, SEM investigati
ons of irradiated areas show that damage preferably takes place at res
idual steps or other structural defects.