Overview: Far-Ultraviolet and Broadband Mirror Coatings
Far-ultraviolet (FUV) spectroscopy and imaging provide access to star formation, hot interstellar and circumgalactic plasmas, and exoplanet atmospheres, but demand mirror coatings that maintain high reflectance at wavelengths where most optical materials are strongly absorbing. Aluminum protected by a fluoride overcoat remains the reference reflector into the FUV, yet its performance is highly sensitive to deposition conditions and overcoat design. ZeCoat develops protected-aluminum coatings that maximize FUV reflectance while providing the environmental durability required for extended ground- and space-based operation.
The Technology
FUV reflectance of aluminum is governed by the growth of the native oxide during and after deposition and by the transparency of the protective overcoat. Achieving high short-wavelength reflectance therefore requires precise control of evaporation rate, chamber pressure, substrate preparation, and overcoat deposition, so that the metal is sealed before significant oxidation occurs. ZeCoat employs precision vacuum deposition to produce protected-aluminum coatings with high reflectance, low scatter, and uniformity across the optical surface, and has demonstrated high-temperature protected-aluminum processes on low-expansion substrates. Complementary large-area, multi-source deposition methods extend these recipes to the meter-class primary mirrors envisioned for future FUV/optical/IR (FUVOIR) observatories.
