4 June 2013 Performance measurements of infrared windows with surface structures providing broadband wide-angle antireflective properties
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Abstract
Infrared and visible windows have been fabricated with surface structures that function as broadband and large angle-of-incidence antireflective (AR) coatings. The AR coating is composed of nanoscale pillars formed by reactive ion etching of either a sacrificial buffer layer or the underlying optical substrate using a random array of nickel dots as an etch mask. The Ni dots are formed using a rapid thermal annealing process. The size and spacing of the Ni dots are found to be highly dependent on the initial Ni film thickness and the annealing parameters, as well as the nature of the surface interaction between the Ni and the buffer layer. The diameter and spacing of the resulting pillars can be parametrically tuned between <100 nm to <1 μm to yield broad antireflection properties from visible through the long-wave infrared. Cleartran (ZnS) and ZnSe optical substrates treated (both sides) with the AR coating process have exhibited a greater than 90% transmittance over the short-wave infrared and mid-infrared wavelengths (1-5 μm), and at incident angles up to 70°. The process for fabricating the surface structures is suitable for low-cost application of broadband, wide-angle, AR coatings on curved optical surfaces.
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Byron Zollars, Steve Savoy, Qizhen Xue, Jeremy John, Kyle Hoover, Gabriel Elpers, Roger Wood, "Performance measurements of infrared windows with surface structures providing broadband wide-angle antireflective properties", Proc. SPIE 8708, Window and Dome Technologies and Materials XIII, 87080Q (4 June 2013); doi: 10.1117/12.2016123; https://doi.org/10.1117/12.2016123
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