Preparation and Optical Properties of Sol-Gel SiO2 Antireflective Films

Base-catalyzed sol-gel porous SiO2 antireflective film, an important part of high power laser (such as "Shenguang II" high power laser) facilities, has excellent optical properties and laser damage resistance. However, its low binding strength with optical components can lead to the film frustrated with contact destruction. Based on this antireflective film, a double-layer SiO2 antireflective film (SiO2-MTES) was prepared with improved mechanical strength by coating a thin dense SiO2 film on its surface using dip coating method. Then the SiO2-MTES was compared with a commonly used single-layer ammonia cured SiO2 antireflective film (SiO2-HMDS). Results indicate that the peak transmittance of the fused quartz substrate coated with SiO2-MTES reaches greater than 99.6% at about 800 nm and the zero probability laser damage threshold is measured to be 51.9 J/cm(2) (1064 nm, 9.1 ns) by 1-on-1 laser induced damage threshold testing method, equivalent to the performances of the fused quartz substrate with SiO2-HMDS. Meanwhile, the contact angle between SiO2-MTES and water reaches 117.3 degrees, and the transmittance stability of the SiO2-MTES is good in the high humidity environment with relative humidity greater than 90%. Results of multi-wiping experiments show that the friction-resistant mechanical strength of SiO2-MTES is significantly better than that of SiO2-HMDS, which effectively improves the binding strength between the film and the optical components.