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Journal of Nanophotonics

Broadband and wide-angle hybrid antireflection coatings prepared by combining interference multilayers with subwavelength structures
Author(s): Stéphane Bruynooghe; Marcel Schulze; Michael Helgert; Michel Challier; Diana Tonova; Michael Sundermann; Thomas Koch; Alexandre Gatto; Ernst-Bernhard Kley
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Paper Abstract

To reduce the intensity of the Fresnel reflections of optical components, subwavelength structures prepared by reactive ion etching of SiO2 thin films were combined as the outermost layer with a multilayer system made of conventional thin-film materials. A hybrid coating was thus realized, with the nanoscaled structured outermost layer expected to further improve the antireflection properties of common interference stacks. The microscopic and optical spectroscopic analysis of the subwavelength structures revealed that pillar-shaped nanostructures formed during etching exhibit low-refractive-index properties and have a depth-dependent refractive index. To take into account the refractive-index gradient in the coating design, the optical properties of the nanostructures were modeled using the effective-medium approximation. The calculated average effective refractive index turned out to be 1.11 at 500-nm wavelength. A hybrid coating was designed to minimize the residual reflectance in the 400-nm to 900-nm spectral range for BK7 glass substrate. Experimental results demonstrated that the hybrid-coating approach yields a low residual reflectance with very good omnidirectional properties, owing to the properties of the nanostructured surface.

Paper Details

Date Published: 3 February 2016
PDF: 11 pages
J. Nanophoton. 10(3) 033002 doi: 10.1117/1.JNP.10.033002
Published in: Journal of Nanophotonics Volume 10, Issue 3
Show Author Affiliations
Stéphane Bruynooghe, Carl Zeiss AG (Germany)
Marcel Schulze, Friedrich-Schiller-Univ. Jena (Germany)
Michael Helgert, Carl Zeiss Jena GmbH (Germany)
Michel Challier, Carl Zeiss Jena GmbH (Germany)
Diana Tonova, Carl Zeiss Jena GmbH (Germany)
Michael Sundermann, Carl Zeiss Jena GmbH (Germany)
Thomas Koch, Carl Zeiss AG (Germany)
Alexandre Gatto, Carl Zeiss Jena GmbH (Germany)
Ernst-Bernhard Kley, Friedrich-Schiller-Univ. Jena (Germany)

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