Sol–gel derived ZrO2–SiO2 highly reflective coatings

Abstract 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. SiO 2 was used as the low-refractive index component, and ZrO 2 as the high-refractive index material. The colloidal suspension of ZrO 2 , prepared by hydrothermal hydrolysis of ZrOCl 2 , contained monoclinic nanocrystalline ZrO 2 , with an average particle size of 15 nm. A minimum transmittance of 1% near 1064 nm was obtained from a 20-layer SiO 2 –ZrO 2 /PVP multilayer film. The ZrO 2 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 SiO 2 –ZrO 2 /PVP film was observed using a Q-switched Nd:YAG high power laser at a wavelength of 1.06 μm and with a pulse width of 2.5 ns.