Durability Improvements for Detector Antireflection Treatments

Anti reflection (AR) coatings, used for detectors in space-based long-wavelength infrared (LWIR) sensor systems, are subjected to a variety of environmental loadings in space such as extreme temperature variations and solar radiation. The resulting damage to the coatings can cause inoperability of the detectors. Consequently, there is a need of significant improvements to broadband transmission and durability of antireflective treatments over those currently used for space detectors. In this program, Surmet will develop antireflective surface treatments to improve broadband transmission and durability of the space detectors. The proposed Phase I effort will consist of the application of antireflective coatings and surface relief structures on cadmium-zinc telluride (CZT) substrates. Both the coatings and the surface relief structures will be characterized and evaluated for durability, optical transmission, and reflection loss. Prototype CZT coupons (of a size and thickness suitable for an actual detector), with an antireflective surface treatment on one side and an average transmission in excess of 72% over 8-12 micron waveband, will be delivered at the end of Phase I. Improved durability and cost effectiveness will be demonstrated during the proposed phase I option.