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Proceedings Paper

Recent developments in highly durable protective/antireflection coatings for Ge and ZnS substrates
Author(s): Wasim Hasan; Steven H. Propst
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Paper Abstract

Antireflection coated ZnS and Ge substrates erode under severe operational environmental conditions. High velocity water drop impact and high velocity sand particle impact are primarily military concerns that originated with the advent of faster aircraft. High speed flight through rain and sand storms seriously erodes forward facing components such as infrared transmitting windows and/or domes. This erosion of windows and/or domes causes reduction in transmission, resulting in the reduction of detection and recognition sensitivity of the electro-optical sensor. A single film of one quarterwave thick hard-carbon coating has been used on germanium to increase optical transmission (reducing Fresnel's reflection losses on Ge surface) as well as to reduce rain and sand impact damage to some extent, at a lower speed. At high speed, the damage becomes more severe, resulting in unacceptable large transmission losses. Recently, new hard carbon coatings have been developed for Ge which have substantially increased the damage threshold of the coated substrates. The rain erosion test was performed at Wright-Patterson AFB facility in Dayton, Ohio, and the sand tests were performed at PDA Engineering in Santa Ana, California. In addition, a multilayer AR coating utilizing hard carbon film as one of the low index films has also been developed at Hughes for ZnS substrates. The optical properties, rain erosion, sand erosion, and sand abrasion test results of these coatings are also presented in this paper.

Paper Details

Date Published: 4 November 1994
PDF: 8 pages
Proc. SPIE 2253, Optical Interference Coatings, (4 November 1994); doi: 10.1117/12.192093
Show Author Affiliations
Wasim Hasan, Hughes Danbury Optical Systems, Inc. (United States)
Steven H. Propst, Hughes Santa Barbara Research Ctr. (United States)

Published in SPIE Proceedings Vol. 2253:
Optical Interference Coatings
Florin Abeles, Editor(s)

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