Single layer Al (2) O (3) .H (2) O and multilayer Al (2) O (3) .H (2) O-SiO (2) optical coatings prepared from colloidal suspensions
Applied Optics 28(18): 4013-4016
ISSN/ISBN: 1559-128X PMID: 20555813 DOI: 10.1364/ao.28.004013
Single layer coatings of Al(2)O(3).H(2)O 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/cm(2), respectively.