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Proceedings Paper

Complex Index Interference Films On Metal Substrates
Author(s): Keith A. Snail
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Paper Abstract

A spectral reflectance model for a homogeneous complex index film on a metal substrate is presented which illustrates the importance of interference in producing selective absorption. In this model the real part of the film's index of refraction (n) and the film thickness (d) are chosen to satisfy the normal quarter wave condition at a shoulder wavelength of approximately 1-2 microns, while the imaginary part of the film's index (k) is chosen so as to match amplitudes of a front and back surface reflected wave. In order to isolate the effects of interference, all optical constants are assumed to be independent of wavelength and all surfaces are considered smooth. The conditions under which zeroes in the reflectivity occur are investigated with a vector diagram technique and the effect of varying these conditions on the spectral reflectivity is studied. A tradeoff between the solar absorptance and the width of the visible-infrared transition region is shown to be a natural consequence of the conditions placed on (n,k) of the interference film. The effect of grading the film's index on this tradeoff can be treated analytically without approximating the film as a stack of homogeneous layers. This analytical approach is outlined and preliminary results are presented.

Paper Details

Date Published: 2 November 1984
PDF: 7 pages
Proc. SPIE 0502, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion III, (2 November 1984); doi: 10.1117/12.944790
Show Author Affiliations
Keith A. Snail, Naval Research Laboratory (United States)


Published in SPIE Proceedings Vol. 0502:
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion III
Carl M. Lampert, Editor(s)

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