There are a lot of ways to make large commercial sapphire crystals. But none of them really work for making large sapphire windows using sapphire’s a-plane. We mean really wide so that they can be used in a military plane as a targeting system window. So, the Air Force Research Laboratory (AFRL) asked Rubicon Technology to develop a new growth platform for very large polished sapphire infrared (IR) windows. The project is supported by a grant from the AFRL, with a total value of $4.7 million over three years.
Sapphire is perfect for military and other high-performance applications due to its hardness and strength, transparency in the visible and IR spectrum, thermal conductivity, thermal shock resistance, abrasion resistance, high melting point and chemical inertness. The project will begin with intermediate sizes, then will step it up to windows as large as 36 x 18 x 0.8 inches.
Why do we need this new method? Existing methods used to produce sapphire windows don’t meet the demands of military applications for thickness and size. Rubicon’s new technological platform will grow panels approximately two inches thick, which can be cut into multiple windows of varying thickness. The new method also allows growth of very large windows up to 36 x 18 inches. This is an improvement over smaller faceted windows that require piecing together for large applications.
The sapphire windows for the AFRL will be applied to fighter jet targeting systems. For example, the Lockheed-Martin F-35 Lighting Joint Strike Fighter’s fuselage has a durable sapphire window in the fuselage for use by the Electro-Optical Targeting System (EOTS). The sapphire is preferred due to its durability, hardness and strength and the way it allows transmission light in the IR spectrum.
Lockheed-Martin F-35 Lightning II Joint Strike Fighter, http://airsoc.com/articles/view/id/4fe4b7f8c6f8fa2443000009/lockheed-martin-f-35-lightning-ii-joint-strike-fighter
Rubicon Technology, http://rubicon-es2.com/index.php?page_id=23