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Proceedings Paper

High durability antireflection coatings for silicon and multispectral ZnS
Author(s): Shay Joseph; Orna Marcovitch; Ygal Yadin; Dror Klaiman; Nitzan Koren; Hedva Zipin
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Paper Abstract

In the current complex battle field, military platforms are required to operate on land, at sea and in the air in all weather conditions both day and night. In order to achieve such capabilities, advanced electro-optical systems are being constantly developed and improved. These systems such as missile seeker heads, reconnaissance and target acquisition pods and tracking, monitoring and alert systems have external optical components (window or dome) which must remain operational even at extreme environmental conditions. Depending on the intended use of the system, there are a few choices of window and dome materials. Amongst the more common materials one can point out sapphire, ZnS, germanium and silicon. Other materials such as spinel, ALON and yittria may also be considered. Most infrared materials have high indices of refraction and therefore they reflect a large part of radiation. To minimize the reflection and increase the transmission, antireflection (AR) coatings are the most common choice. Since these systems operate at different environments and weather conditions, the coatings must be made durable to withstand these extreme conditions. In cases where the window or dome is made of relatively soft materials such as multispectral ZnS, the coating may also serve as protection for the window or dome. In this work, several antireflection coatings have been designed and manufactured for silicon and multispectral ZnS. The coating materials were chosen to be either oxides or fluorides which are known to have high durability. Ellipsometry measurements were used to characterize the optical constants of the thin films. The effects of the deposition conditions on the optical constants of the deposited thin films and durability of the coatings will be discussed. The coatings were tested according to MIL-STD-810E and were also subjected to rain erosion tests at the University of Dayton Research Institute (UDRI) whirling arm apparatus in which one of the coatings showed no rain drop impact damage at all.

Paper Details

Date Published: 2 May 2007
PDF: 10 pages
Proc. SPIE 6545, Window and Dome Technologies and Materials X, 65450T (2 May 2007); doi: 10.1117/12.713081
Show Author Affiliations
Shay Joseph, Rafael-Optical Components Ctr. (Israel)
Orna Marcovitch, Rafael-Optical Components Ctr. (Israel)
Ygal Yadin, Rafael-Optical Components Ctr. (Israel)
Dror Klaiman, Rafael-Optical Components Ctr. (Israel)
Nitzan Koren, Rafael-Optical Components Ctr. (Israel)
Hedva Zipin, Rafael-Optical Components Ctr. (Israel)

Published in SPIE Proceedings Vol. 6545:
Window and Dome Technologies and Materials X
Randal W. Tustison, Editor(s)

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