Environmental Stable SiO2 Antireflective Coating Modified via NH3/HTMS Vapor Phase Treatment

Sol-Gel derived silica antireflective coatings have been widely used in high power laser system because of their ultra-low refractive index and high laser damage threshold. However, water vapor and volatile organic compounds in the laser system contaminate these coatings and reduce their antireflective efficiency and laser damage resistance. In this work, environmental stable SiO2 antireflective coating was prepared by vapor phase treatment of ammonia and HTMS. Monodisperse colloidal silica sol was synthesized by Sol-Gel method using tetraethylor-thosilicate (TEOS) as precursor, ammonia as catalyst, and ethanol as solvent. The silica coatings were then deposited on the BK7 glass using dip-coating method. Ammonia vapor phase treatment and HTMS vapor phase treatment were combined to improve the environmental stability of the antireflective coating. The peak transmittance of the BK7 glass coated with the modified coating decreased only 0.03% after being exposed in the humid environment for 2 m. Meanwhile, the transmittance curve of the BK7 glass coated with modified coating had almost no change after being placed under low vacuum condition with oil pollutants for 2 m, indicating that the coating modified via combined vapor phase treatment of ammonia and HTMS possessed an excellent environmental stable performance. Therefore, the combination of ammonia and HTMS vapor phase treatment is effective to improve the working life of SiO2 antireflective coating in high power laser system.