High performance, stable, and scalable UV aluminum mirror coatings using ALD

This proposal aims to further develop mirror coating technologies that can meet the needs of future large aperture space telescopes on mission concepts such as the Large UV/Optical/IR Surveyor (LUVOIR) and the Habitable Exoplanet Observatory (HabEx), with a thin film coating technology that can offer several advantages over the current state-of-the-art. In previous programs, work at NASA's Jet Propulsion Laboratory (JPL) has resulted in the development of new atomic layer deposition (ALD) processes for ultraviolet protective coating materials such as MgF2, AlF3 and LiF. This has led to the demonstration of protected aluminum mirror coatings by combining these ALD materials with evaporated aluminum. To date, these are the only high performance FUV mirrors (>80% R at 120 nm) with protective coatings that are not deposited by conventional physical vapor deposition methods like evaporation and sputtering. The self-limiting nature of the ALD process holds the promise of improved reflectance uniformity and improved coating stability. In this proposed effort we will take these laboratory demonstrations and fully characterize their environmental stability and investigate scaling trends toward the meter-class by utilizing the combined expertise of team members at NASA JPL, the University of Colorado Boulder (CU), and the University of California Santa Cruz (UCSC). The main objectives of this proposal are: 1. Perfecting the combination of ALD processes and Al PVD to produce wide band pass (90-2500 nm) aluminum mirror coatings with high reflectivity (~90%), placing particular emphasis on high reflectivity performance in the FUV. We will demonstrate full mirror coatings on shaped optics relevant to sounding rocket and cubesat programs at CU. 2. Studying and ensuring long term performance stability by comparing the most promising ALD coating methods directly with PVD-based mirrors for the first time under identical accelerated aging tests. 3. Demonstrating scalability trends towards large (>1 m) size mirrors. In part, this will utilize the unique large area ALD system developed at UCSC specifically for astronomical mirror systems. 4. Work with industry partners to refine our understanding of aluminum deposition with respect to form birefringence, microstructure, and overcoat stability in the context of compatibility with ALD overcoats as well as the future needs of LUVOIR or HabEx. 5. Measurement and modeling of reflectance uniformity, wavefront error, and polarization retardance over the full aperture of shaped optics in the wavelength bands of interest to exoplanet coronagraphs. The advancement in Technology Readiness Level (TRL) achieved by meeting these objectives will allow this new mirror coating technology to reach TRL 5 from its current TRL 3 status.

The Strategic Astrophysics Technology program (SAT) supports focused development efforts for key technologies to the point at which they are ready to feed into major missions in the three science themes of the Astrophysics Division: Exoplanet Exploration, Cosmic Origins, and the Physics of the Cosmos. This program is specifically designed to address middle technology readiness level (TRL) "gaps" between levels 3 and 6: the maturation of technologies that have been established as feasible, but which are not yet sufficiently mature to incorporate into flight missions without introducing an unacceptable level of risk. NASA does not require a data management plan for proposals to SAT.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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