STRUCTURAL INFLUENCES ON THE LASER DAMAGE RESISTANCE OF OPTICAL OXIDE COATINGS FOR USE AT 1064 NM

Optical coatings of titania (TiO2) and tantala (Ta2O5) prepared by reactive r.f. diode and d.c. plasmatron sputtering were investigated for the influence of structural properties on the 1064 nm laser damage resistance. Using various methods of characterizing the compositional, crystallographic, microstructural and optical properties, it was found that the damage thresholds are directly related to the content of oxygen in the films in excess of the stoichiometric value, whereas grain sizes and refractive indices show no systematic influences valid for both oxide materials. The highest oxygen-to-metal atomic ratios and thus the highest damage thresholds were achieved by the use of r.f. diode sputtering. X-ray photo spectroscopy investigations of tantala coatings with different oxygen-to-tantalum atomic ratios up to 2.75 revealed for both constituents of the oxide only binding energies representative for tantalum pentoxide. © 1990.