Sol-gel derived ZrO2-SiO2 highly reflective coatings

In this paper. colloid-based highly reflective coatings consisting of alternating layers of quarterwave thick high- and low-refractive index components were deposited on glass substrates by a sol-gel spin-coating method. SiO2 was used as the low-refractive index component, and ZrO2 as the high-refractive index material. The colloidal suspension of ZrO2, prepared by hydrothermal hydrolysis of ZrOCl2, contained monoclinic nanocrystalline ZrO2, with an average particle size of 15 nm. A minimum transmittance of 1% near 1064 nm was obtained from a 20-layer SiO2-ZrO2/PVP multilayer film. The ZrO2 particles were deposited in an ethanolic suspension containing polyvinylpyroldione (PVP) as a binder. The maximum transmittance in the visible range was about 85%. A 1-on-1 laser-induced damage threshold of 16 J/cm(2) for the 20-layer SiO2-ZrO2/PVP film was observed using a Q-switched Nd:YAG high power laser at a wavelength of 1.06 mu m and with a pulse width of 2.5 ns. (C) 2000 Elsevier Science Ltd. All rights reserved.