Nano-Silica-Based Double-Layer Antireflective Coatings with Mildew Resistance and Moisture Resistance for KDP Crystals.

Sol-gel nano-silica antireflective (AR) coatings with moisture resistance are widely used for optical elements, such as potassium dihydrogen phosphate (KDP) crystals, but their mildew resistance is often disregarded. This work reports a double-layer AR coating with moisture resistance and mildew resistance for KDP crystals. A polydimethylsiloxane-modified dense silica coating and a quaternary ammonium salt (QAS) modified nanoporous silica coating are selected as the bottom layer and top layer, which effectively serve as a moisture barrier and an antireflection layer, respectively.