Single layer coatings of Al2O3·H2O have been prepared on fused silica and BK-7 substrates from aqueous colloidal suspensions of hydrated alumina at room temperature. These coatings were porous and had a refractive index of ∼1.44. Multilayer, high reflectivity, dielectric coatings were also prepared by laying down quarterwave-thick, alternating coats of this alumina with silica, also prepared from colloidal suspension, and having a refractive index of 1.22. To achieve 99% reflectivity, 30–35 layers were required. Single shot, laser damage threshold measurements at 1064 nm wavelength with a pulse length of 10 ns were carried out on both the single layer and multilayer system. The thresholds averaged 21 and 12 J/cm2, respectively.
© 1989 Optical Society of America
Ian M. Thomas, "Single layer Al2O3·H2O and multilayer Al2 O3·H2 O-SiO2 optical coatings prepared from colloidal suspensions," Appl. Opt. 28, 4013-4016 (1989)