PROCESS FOR FORMING AN ENVIRONMENTALLY STABLE OPTICAL COATING AND STRUCTURES FORMED THEREBY

摘要

An optical coating which is stable upon sustained exposure to water vapor is provided by a low-temperature photochemical vapor deposition process. First, there are provided a first vapor phase reactant containing silicon, a second selected vapor phase reactant, and an oxygen-containing precursor which are capable of interacting upon radiation inducement to form the corresponding oxides of the vapor phase reactants. A chosen substrate is exposed to the first and second selected vapor phase reactants in predetermined proportions and the chosen oxygen-containing precursor in the presence of radiation of a predetermined wavelength to induce a reaction to form a coating on the substrate. The coating comprises a silicon dioxide containing a predetermined proportion of the second oxide, such as lead oxide. The coating maintains stable optical properties upon sustained exposure to water vapor, as indicated by stable peak wavelength of reflectance and stable optical transmittance. Graded index optical elements as well as quarterwave stack structure may be formed by this process.