Conformal Thin Film Epitaxial Sapphire Coating for Window/Dome Refurbishment and Repair

The use of sensor systems in the IR spectrum have become widespread in the military services over the last fifty years. The sensors used by the military services can be found on vehicles and systems ranging from simple troop transport systems to drones and seeker systems. As the theater of operation in which these systems have deployed has moved into desert environments and environs with prolonged exposure to salt spray, the degradation of the windows and domes that protect these systems has become a challenge. These caustic operating environments accelerate the degradation of these windows and domes through pitting, gouging, scratching, wide-area abrasion, and surface contamination from operational environments. Although methods have been adopted to repair the coatings often used in these IR applications, there is not currently a satisfactory solution for the repair of the underlying single crystal or poly-crystalline substrate (e.g., sapphire, spinel, Silicon (Si), or Germanium (Ge)). Past attempts at repair of these windows have resulted in degraded optical quality, due to mismatches in the indices of refraction, stress, or thermal expansion.Summit Information Solutions, Inc. proposes the development of a polishing and coating process. This polishing process will use a standard industry practice for ultra-low roughness polishing of dielectric materials. This will first require a rough polish of the sapphire windows to remove non substrate material, such as metal or dielectric coatings, surface abrasion, scratches, and other surface damage. Summit will use an automated polishing stand with controlled polishing head. Summit has previously used this process to prepare X-Ray mirror substrates to an RMS roughness of less than 0.4 angstroms. After the sapphire substrates are prepared through the above polishing process. Summit will rebuild the sapphire surface through epitaxial growth using Atomic Layer Deposition (ALD). Summit has experience with epitaxial growth of sapphire using the proposed technique and has the capability to quickly scale up from development to batch process manufacturing without significant retooling.