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Proceedings Paper

Ultrathin lamellar gratings as solar-selective coatings
Author(s): Martin Brunotte; Rudolph H. Morf; Karl-Heinz Schlereth; Harald Boettner
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Paper Abstract

Ultra-thin lamellar gratings represent a new kind of transparent heat mirror based on the principle of waveguides. Wavelengths shorter than double the waveguide diameter are propagated, while longer wavelengths are reflected at the opening of the waveguide. Parallel metal strips mounted perpendicular to a transparent surface exhibit equivalent behaviour for waves polarized perpendicular to the strips. For unpolarized radiation, two of these lamellar gratings have to be crossed. These gratings are manufactured by embossing a profile of right-angle triangles onto a transparent substrate. They have a period and depth of approximately 0.8 m. The vertical faces of the profile are then covered with a thin conducting metal layer by oblique evaporation. According to theoretical calculations, the JR-reflectance of the optimized grating is as high as the reflectance of a coherent metal coating, whereas the solar transmittance is very high even for diffuse radiation. The grating has a very sharp cut-off wavelength which can be adjusted depending on the application. A nickel master profile for embossing has been manufactured by photolithographic techniques. The structure has been replicated on transparent PVC. First measurements of evaporated gratings show the expected characteristics.

Paper Details

Date Published: 1 August 1990
PDF: 10 pages
Proc. SPIE 1272, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion IX, (1 August 1990); doi: 10.1117/12.20428
Show Author Affiliations
Martin Brunotte, Fraunhofer-Institut fuer Solare Energiesysteme (Germany)
Rudolph H. Morf, Paul Scherrer Institute (Switzerland)
Karl-Heinz Schlereth, Fraunhofer-Institut fuer Physikalische Messtechnik (Germany)
Harald Boettner, Fraunhofer-Institut fuer Physikalische Messtechnik (Germany)

Published in SPIE Proceedings Vol. 1272:
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion IX
Claes-Goeran Granqvist; Carl M. Lampert, Editor(s)

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