For the past 15 years, the SPIE Window and Dome Technologies and Materials Conferences have been a community focal point for dissemination of information on the state of the art in materials, properties, and design, evaluation, and test methods for high-performance windows. This paper reviews developments over that time, the current state of window development, and future expectations. Examples are used to illustrate both progress and the need for continued development.
An optical technique for measuring surface stress in chromium-doped sapphire windows is reported. The approach utilizes the well-known effects of temperature and stress on the spectral profile of chromium ion fluorescence in crystalline sapphire. In this study, the sapphire samples were selectively doped with a surface concentration of chromium ions, which provided a direct measure of the stress and temperature in the surface region of the window. A series of fluorescence measurements were performed to calibrate the effects of temperature and mechanical stress on the spectral characteristics of the surface fluorescence. The results of this laboratory study are currently being developed into a dynamic, non-contact probe of stress in infrared seeker windows while under simulated conditions of flight.