Laser damage studies of polymer oxide coated silica optics at 350 nm

A single layer SiO2 film with graded porosity applied from a polymer solution derived from organometallic silicon compounds on fused silica lenses provides antireflectivity over the transmission range covering the first, second, and third harmonics of neodymium glass lasers. The damage thresholds of initial samples at 350 nm (3ω) varied from less than 1 to 9 J/cm2. The main causes of this large variation in the damage threshold were determined to be substrate polishing, substrate surface cleaning, and the coating solution chemistry and processing, which, under certain conditions, leads to carbon formation during the heat treatment of the coating.