Scale-up of the Heat Exchanger Method (HEM) Sapphire Crystal Growth Process for IR Window Applications

The increased use of high resolution Infrared (IR) sensors is leading to growth in demand for large aperture, high optical quality sapphire for a variety of DoD programs. Increasing the size of sapphire windows can improve sensor capabilities while at the same time reduce system cost, increase reliability and decrease maintenance issues. Crystal Systems, Inc. (CSI) currently produces 15" diameter, high quality sapphire boules using the Heat Exchanger Method (HEM) of crystal growth. Plates fabricated from these boules supply JSF EOTS windows, THAAD windows, the Lockheed Sniper Pod and other DoD programs. The goal of this program is a production ready sapphire growth process for the manufacture of IR sensor windows for military applications. The Phase I objective is to demonstrate the feasibility (to MRL 4) of scaling the HEM growth process to 25" diameter sapphire to supply these large plates. The deliverable at the end of Phase I is: a manufacturing process development plan with progress and completion performance goals for this scale up. BENEFIT: The successful outcome of this program after Phase II will result in an increased MRL to MRL 7 or above for Crystal Systems’ production process for large high quality sapphire windows for DoD applications such as IR sensor windows and transparent armor. The HEM process produces the highest quality sapphire, and the resulting high yields will produce a robust, cost effective, and reliable supply of windows. Secondary benefits include establishing a second supplier for large 14” x 20” x 0.8” EOTS sapphire windows, and the possibility to produce c-axis blanks. In addition there are numerous commercial applications for sapphire, including LED substrates, endoscope windows, machine vision windows and sight glass windows, wafer carriers, and mechanical applications. Additionally, if unit production costs are reduced as a result of a scale-up for large area sapphire windows, other large area window products will see commercialization and the unit cost of existing commercial products will be reduced.