Reduction in NIR absorption of Spinel through annealing

Transparent magnesium aluminate spinel (MgAl2O4) has been developed as an optical ceramic for a variety of applications, including as windows. As a broadband, ultraviolet (UV) thru midwave infrared (MIR) material, it has been developed for windows and has many desirable properties compared with alternative infrared glasses and other transparent ceramics. Current efforts to advance high strength spinel manufacturing processes have demonstrated progress toward large format windows. Although low-absorption spinel, specifically in the near-infrared (NIR) has been demonstrated previously, additional processing is required for new, large-scale spinel manufacturing processes to decrease the effects of impurities near one-micron wavelengths. In this work we present recent results that show measured absorption near 1 μm is reduced by annealing, which reduces effects of trace impurities. Experimental results from photo-thermal common-path interferometer measurements are reported.