Optical interference coatings prepared from solution

Recently E. M. Laboratories introduced colloidal silica and titania solutions from which one can produce optical thin films. Single quarterwave V-coats and three-layer AR coatings for the visible as well as four-and five-layer AR coatings at 1.06 microm were prepared using these solutions. Reflection spectra and ellipso-metric measurements showed that these films are essentially optically equivalent to those prepared by e-beam evaporation. However, the former films lacked the rub durability of the latter films. This deficiency was traced by frustrated multiple internal reflectance (FMIR) spectroscopy and by Auger electron spectroscopy (AES) to organic solvents trapped within the titania matrix. X-ray diffraction (XRD) showed the silica films to be amorphous whereas the titania films were slightly crystalline with the anatase structure.