AR Coated Zinc Sulfide Advanced Window Technology

Multispectral zinc sulfide (ZnS) has been identified as a candidate seeker window material for defensive interceptor applications. Zinc sulfide is currently being tested for thermophysical and optical properties to confirm its performance and validate analytical predictions. The ZnS currently being tested does not contain an antireflective (AR) coating. Due to the increase in spectral bandwidth for ZnS, a broadband AR coating will be required to optimize its transmission characteristics. The objective of this effort is to develop and demonstrate multilayer antireflective coating(s) applied to ZnS. Optical transmission testing will be conducted at incidence angles from near normal up to 60 degrees at ambient and service temperature levels using the a bandwidth of 3um to 11um. Material test coupons will be prepared using current THAAD specifications for machining and polishing of the ZnS substrate surfaces. The AR coatings will be selected based on durability, ability to withstand the thermal environment, compatibility with to the ZnS bandwidth, abrasion resistance and cost. The resulting data will be compared to uncoated materials and analysis conducted to identify application performance capabilities.