High performance DLC/BP and ZnS/YbF3 double-layer protective and antireflective coatings

A double-layer coatings structure on the surface of ms-ZnS substrate is designed and fabricated. The outer face of the ms-ZnS is coated with DLC/BP as high performance protective and antireflective coatings, and the inner face is coated with YbF3 and ZnS as high efficient antireflective coatings. The transmittance, nano-hardness and environmental durability of the coated ms-ZnS are measured by FTIR spectroscopy, nano-hardness tester and simulative harsh environmental test specified by MIL-48616, respectively. It shows that, in the waveband of 8–12 μm, the measured maximum transmittance is about 93.3% and the average transmittance is about 87.9%. After coated with DLC/BP, the nano-hardness of ms-ZnS samples increases from 2.5 to 19.5 GPa. The coated ms-ZnS passes the environmental tests, which indicates that it can meet the demands of (long-wave infrared) LWIR electro-optics systems working in harsh environment.