In continuation to our search program on laser-damage resistant coatings and in synergy with the Lawrence Livermore National Laboratory, we have prepared porous single layer coatings of ZrO2 on fused silica and BK-7 substrates from suitable aqueous colloidal suspensions of crystalline zirconia at room temperature. By adding judiciously a soluble inorganic binder to the suspension prior to application, it has been possible to increase substantially both the coating refractive index and the abrasion-resistance. The optimum binder concentration was about 30 % and at this level the optical properties and laser damage threshold of the zirconia coating were satisfactory. Multilayer high reflectivity dielectric coatings were also elaborated by laying down quaterwave-thick, alternating coats of this binder-aided zirconia with silica, also prepared from colloidal suspension. To achieve 99 % reflectivity, 17-19 layers were required. Single shot (1- on-1), laser damage tests at 1064-nm wavelength with a pulse length of 3-ns were carried out on both the single layer and multilayer systems. The thresholds averaged 8.6 and 8.2 J/cm2 respectively. With a laser- annealing post-treatment, n-on-i threshold values were higher than the 1-on-1 figures by a factor of about 1.5.
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