Stabilization and Characterization of Nanosized Niobium and Tantalum Oxide Sols — Optical Applications for High-Power Lasers

Stable nanosized particles of niobium and tantalum oxides were obtained by hydrolysis of the metal ethoxides in ethanol with triethylamine. These sols were amorphous hydrated oxides M2O5·nH2O. They were used to prepare thin porous films on SiO2 disks via spin-coating techniques. These coatings displayed thicknesses ranging from 100 to 300 nm and a refractive index of about 1.7. Laser damage tests at 1053-nm wavelength with a pulse duration of 3 ns were conducted on the single-layer systems. Ta2O5 coatings exhibited much higher threshold values (averaging 14.5 ± 2.1 J/cm2) than those of Nb2O5 (averaging 8.3 ± 1.6 J/cm2). Buildup of multilayer stacks of high- and low-index materials was prevented because of internal stress.