Ultrathin lamellar gratings as solar-selective coatings

Martin Brunotte; Rudolph H. Morf; Karl-Heinz Schlereth; Harald Boettner

doi:10.1117/12.20428

1 August 1990 Ultrathin lamellar gratings as solar-selective coatings

Martin Brunotte, Rudolph H. Morf, Karl-Heinz Schlereth, Harald Boettner

Proceedings Volume 1272, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion IX; (1990) https://doi.org/10.1117/12.20428
Event: The International Congress on Optical Science and Engineering, 1990, The Hague, Netherlands

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.

Citation Download Citation

Martin Brunotte, Rudolph H. Morf, Karl-Heinz Schlereth, and Harald Boettner "Ultrathin lamellar gratings as solar-selective coatings", Proc. SPIE 1272, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion IX, (1 August 1990); https://doi.org/10.1117/12.20428

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