The use of ion beam sputtered optical coatings as protective overcoats

Abstract

Diamond turned aluminium mirrors are being used more often in forward looking infrared (FLIR) imaging systems (operating in the 8–12 μm region) because they provide high optical performance at low cost. The original high reflectivity of these surfaces must be maintained through military standard humidity/temperature cycling tests. We have developed ion beam sputtered Y2O3 as a protective coating that meets all optical and environmental requirements. Data are presented that show that ion beam sputtered optical coatings are much less permeable to water than electron-beam coatings while retaining many of the desirable features of e-beam coatings. The deposition process and the properties of the coatings will be presented. Thin protective coatings of Y2O3 that exhibit very little angular dependence in reflectivity on aluminum have been prepared by ion beam sputtering.