Method for making a tantala/silica interference using heat treatment

Abstract

A method for making a tantala/silica interference filter on a vitreous substrate, which filter retains integrity at temperatures in excess of 600.degree. C., includes the steps of depositing by low pressure chemical vapor deposition a first coating of tantala/silica on the substrate, heat treating the first coating, and depositing by low pressure chemical vapor deposition a second coating of tantala/silica, the first and second coatings in combination providing a tantala/silica interference filter with a thickness of at least 3.5 microns on the vitreous substrate. There is further presented an electric lamp having an envelope and an interference filter applied thereto, in accordance with the above method.

Dependencies are inferred from the claim text.