The presentthesis, aimed to design, fabrication and hardening of multi-layers broadband anti-reflection coating in the range from 8 to 12 ?m by using germanium and zinc sulfide, on zinc sulfide substrate. We selected Ge as high index material and ZnS as low index material. The design was performed by the Essential Macleod program. The optimization was performed by the simplex method in which the desired transmission is obtained by changing the thickness of the layers. Deposition was performed by physical vapor deposition (PVD) technique in a vacuum chamber, by using electron gun and thermal boat. The arrangement and optimized thickness of the layers in the fabricated antireflection coating are as follows: ZnS substrate/Ge(162 nm) /ZnS(395 nm)/Ge(551 nm)/ZnS(1293 nm). The coating was studied by FTIR, nanoindentation, AFM and environmental tests. The FTIR spectroscopy shows that the coating increases the IR transmission by about 22 - 26 %. An average transmittance of 93% was achieved in the wavelength range of 8-12 ?m. In the next step, in order to improve the mechanical properties of the coating, we deposited a bilayer of Y 2 O 3 /Carbon on the coating. Nanoindentation test shows that the bilayer enhances the mechanical properties. Finally the environmental analyzes such as abrasion, adherence, salt spray, thermal shock and humidity were performed on the coating. The results show that the four layers coating with the protective bilayer of Y 2 O 3 /Carbon has successfully passed durability and environmental tests.
