This paper discusses achromatic antireflection coatings of increased optical efficiency with a residual reflectance of ρave=0.1-0.3% in the spectral regions 3-5 and 8-12.5 µm for silicon, germanium, and zinc selenide. Designs are presented for such coatings of various compositions, based on operationally stable thin-film materials. The spectral characteristics of the reflectance are also shown for the coatings under consideration.
R. S. Sokolova, A. V. Mikhailov, and G. A. Muranova, "Antireflection coatings of increased optical efficiency for the IR region," J. Opt. Technol. 72, 795-798 (2005)