Ion-assisted deposition of nontoxic coatings for high-power CO2 laser optics

Rare earth fluorides have been investigated as possible coating materials for carbon dioxide laser optic components. AR and PR coatings on ZnSe substrates were produced by means of ion assisted deposition (IAD) of YF3 and YbF3. Optics with total absorption of about 0.1% and with damage thresholds of up to 30 J/cm2 were produced. Effects of IAD on stoichiometry and chemical state of the rare earth ions have been examined by x-ray photoelectron spectroscopy (XPS). In-situ XPS revealed that ion bombardment, as used in IAD, and sputter cleaning result in fluorine deficient films. Oxygen incorporation during preparation could be kept below 1 - 5at%.