Silica antireflective films were prepared on flat glass substrates by spraying method. By adding n-propanol, isopropanol, n-butyl alcohol and low vapor pressure solvent 1,3-butanediol to form gradient volatilization solvents, the “whitish” in color of coating was solved. Spray coating is a single side coating technology which is suitable for flat or weakly bent substrates. This method can be flexibly applied to single-side coating, double-side heterogeneous coating and rapid coating of large-scale components. The results show that the antireflection coating prepared by spraying method has good optical properties, the transmittance can reach 99.61%, the root mean square roughness is 1.22 nm and the uniformity of the coating was smooth. The spraying method has been successfully applied to the preparation of antireflection films on flat substrates.
Modified antireflective thin films for optical crystals are developed by sol gel chemistry. Hexamethyldisilazane is added
to silica sol to prepare modified sol by the Stöber method. The particle size distribution of the modified sol is found to
have good uniformity, with an average particle diameter of about 42.14 nm. This sol can be used to prepare antireflective
films with low refractive index of about 1.2. Homogeneous double layered films of antireflective and moisture resistant
properties are demonstrated to coat small square sized KH<sub>2</sub>PO<sub>4</sub>/KD<sub>2</sub>PO<sub>4 </sub>crystals through a combination of dip and spin
coating. The modified antireflective films display residual reflectivity close to zero, and laser induced damage threshold
of 10.9 J/cm<sup>2</sup> (pulse wavelength: 355nm, pulse width: 3ns) measured by raster scan method.