Optical multilayer thin-film filters and methods for manufacturing same

Abstract

Optical multilayer thin-film filters (OMTFFs) are disclosed. An exemplary filter includes a transparent substrate, a multilayer film (MF) on a surface of the substrate, and a top layer. The MF is of alternatingly laminated layers of a high-refractive-index (HRI) material and a low-refractive-index (LRI) material. The top layer is on an uppermost layer of the MF and is of a material having atoms of lower atomic weight than atoms of either the HRI or LRI materials. The OMTFFs are made in a vacuum environment by alternatingly laminating respective thin films of the HRI and LRI materials on the substrate. The top layer is formed on the MF. Between forming the MF and top layer is a suppression step in which the newly formed MF is exposed to moisture by briefly venting the vacuum to atmosphere. The moisture inhibits migration of the low-molecular-weight atoms into the HRI and LRI materials.

1 . A method for manufacturing an optical multilayer thin-film filter, comprising:
 performing a first deposition step comprising forming, on a substrate, a multilayer film including multiple alternating thin-film layers of a high-refractive-index material and of a low-refractive-index material;   performing a second deposition step comprising forming, on an uppermost layer of the multilayer film, a top layer of a material including atoms having lower atomic weight than either of the high-refractive-index and low-refractive-index materials; and   between the first and second deposition steps, performing a suppression step that inhibits the atoms of lower atomic weight in the top layer from entering one or more thin-film layers of the multilayer film.   
     
     
         2 . The method of  claim 1 , wherein the suppression step includes exposing the multilayer film to moisture. 
     
     
         3 . The method of  claim 2 , wherein:
 the first deposition step comprises forming respective thin-film layers of the high-refractive-index material and of the low-refractive-index material in an alternating manner by vacuum deposition in a vacuum chamber evacuated to a vacuum level;   the suppression step comprises venting the vacuum chamber to atmospheric pressure; and   the second deposition step comprises forming the top layer by vacuum deposition in the vacuum chamber re-evacuated to a vacuum level.   
     
     
         4 . The method of  claim 1 , wherein:
 the first deposition step comprises forming respective thin-film layers of the high-refractive-index material and of the low-refractive-index material in an alternating manner by vacuum deposition in a vacuum chamber evacuated to a vacuum level;   the suppression step comprises venting the vacuum chamber to atmospheric pressure; and   the second deposition step comprises forming the top layer by vacuum deposition in the vacuum chamber re-evacuated to a vacuum level.