Research on the optical property stability of sol-gel antireflective films

The sol-gel antireflective films have been applied in Large-scale, high-power laser facility for several years to improve its output capability. While, the loose, porous films are under the baneful influence of contamination. The concentration of contamination and the optical properties of films are difficult to be measured when the laser facility is operated. Therefore, it will be important to study the stability of optical property of the coated substitute optics. To study the optical property stability of films in different environments, the samples coated with technological process at present were placed under 10⁵Pa, 10³Pa, 10^-3Pa in laser facility, and spectrum transmittance of them was tested before and during the storage. The spectrum transmittance decrease of the films with storage time is described quantitatively. The tested results shows that, the sol-gel antireflective films consequently can maintain its high transmittance under room pressure. The transmittance will be decreased significantly under 10^-3Pa owing to plenty of contamination. The test under 10³Pa shows that there is much more contaminants on higher fluent. Further experiment after intensified NH₃ and HMDS posttreatment has been performed at the same time. The results shows that these samples have lower rate of the transmittance decrease. Both the control of the cleanliness and the intensified post-treatment will extend the lifetime of the sol-gel antireflective films.