Antireflection coatings designed for two different infrared substrates.

It is shown that it is possible to design normal-incidence antireflection coatings that simultaneously reduce the reflectance of two different substrates. Although this is at the expense of some deterioration in performance when compared with that of conventional coatings, it can lead to significant time and cost savings in small thin-film production facilities. Numerical examples are presented for ZnS/ZnSe, Si/Ge, and ZnS/Ge substrate pairs. The experimental measurements on one such coating are in good agreement with the calculated performance.