Improvement on contamination resistance to volatile organics and moisture of sol-gel silica antireflective coating for 351 nm laser system by structural modulation with fluorinated compounds

A new silica antireflective (AR) coating with excellent spectral stability and laser-induced damage threshold (LIDT), which are crucial characteristics in high-powered laser systems, was prepared using the sol-gel method. First, aided by 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-octanediol (simplified as DFDO), cross-linking among silica particles was facilitated. Thus high and adjustable inter-particle porosity was obtained and hence the refractive indices of the coatings were modulated. Next, poly(2,2,3,4,4,4-hexafluorobutyl) acrylate (simplified as PHFBA) was utilized to occupy micro-pores inside the coating in order to protect them from contamination. Consequently, the volatile organic and water vapor resistance of resultant DFDO/PHFBA/silica coatings was improved dramatically. By characterizing aggregating manner and stacking condition between particles, the modification process of the proposed AR coating was clarified in details.