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Published online by Cambridge University Press: 15 March 2011
The Boeing Company has developed a unique nanotechnology for antireflective coatings that can perform at near grazing angles (∼80°), in the long wave infrared (LWIR). This technology has been validated through mathematical modeling and the fabrication and testing of small scale components. The coatings were designed to perform best at 10 micron wavelengths, and moderately well over the 8 to 12 micron region. The technology is based upon a circuit analog sheet (capacitive) buried within a dielectric, to produce a reflection that adds out of phase with respect to the face sheet reflection. Since the TE component of the reflection is highest near grazing, the sheet is designed to primarily affect that polarization (low impedance) while leaving the TM wave unaffected (high impedance).
When desired, in order to improve the TM transmission as well as TE, two layers are used at different depths. This dual-layer approach has also been modeled (in closed form), fabricated and tested. Also, explored in this paper, are the impacts of a design that works well azimuthally at grazing angles.
Until recently, the above solution was limited to RF frequencies, but with advances in fabrication it has become possible to fabricate very small nanostructures that operate in LWIR using traditional thin-film vacuum deposition techniques. It is envisioned that eventually such a concept could be used in the visual regime via self assembly.