RAR Nano-Texturing For High Performance Super-Hydrophobic Beam Director Head Windows

As technical requirements for photonic masts become more stringent, the Navy has identified that current anti-reflection (AR) coatings for photonic mast head windows do not adequately meet specifications for bandwidth, durability, and hydrophobicity. In a Phase 2 effort completed in 2022, TelAztec demonstrated and qualified an AR nano-texture solution as a replacement for AR coatings, in a manner that the Technology Readiness Level (TRL) of the solution was significantly advanced. Uniform normal incidence and off-axis reflection levels were shown to be far beyond the capabilities of AR coatings. Extreme hydrophobicity levels were routinely demonstrated, and a new application process was developed for the large head windows for re-application of the surface treatment in the submarine’s operational conditions. The extended lifetime of the hydrophobic head window treatment was qualified through a series of maritime environmental tests with Salt/Fog testing and sea water exposure. In the most important validation of the Phase 2 effort, system level photonic mast testing with photonic mast manufacturer L3 Harris confirmed that the nano-textured head window produced greatly improved performance over the standard LPPM AR coated head window for all optical metrics. By the completion of the Phase 2, the head window inner surface nano-texture treatment was assessed to be at an advanced TRL 7-8, with the outer surface nano-texture that sees continual seawater exposure being rated lower at a 5-6 level. This Commercialization Readiness Program will allow NAVSEA and TelAztec to address the TRL gating items of environmental testing of nano-textured head windows. In particular, TelAztec will nano-texture new head windows for critical hydrostatic pressure testing. These samples will be fully optically characterized before and after hydrostatic pressure testing. The advancements made during this program will move the nano-texture technology for head windows towards to a TRL 8-9 status, potentially leading to a Temp Alteration for integrating a nano-textured window in a submarine photonic mast.In a second but related aspect of the program, TelAztec will develop a super-hydrophobic nano-textured solution for germanium (Ge) head window apertures that are also employed on photonic masts for mid-wave infrared (MWIR) imaging. The hydrophobic properties will be demonstrated to be self-cleaning, and mitigate the on-going issue of salt deposits on the window surface. The nano-textured surface will provide improved AR properties, enabling enhanced imaging capabilities. The solution will also address another issue- the current AR coated germanium head windows have very significant glint issues which leads to exposure to hostile forces. The proposed solution will address this by suppressing visible through SWIR specular reflections while maintaining high transmission in the MWIR, and has the potential for rapid TRL advancement.