Infrared optical glasses for applications in 8-12-microm thermal imaging systems.

Measured data are presented on glass transition temperature, thermal expansion coefficient, and refractive index for glasses in the Ge-As-Se system. The range of reciprocal dispersive power between 8 microm and 12 microm of 110-159 for these glasses is discussed in relation to their basic physical properties, and it is shown that useful compositions for bulk synthesis can be identified. A brief account is given of the preparation techniques, which enable glass to be made with an oxide content of the order of 1 ppm wt as measured by gamma photon activation analysis. The influence of oxide impurity on the transmission is shown for the three glasses Ge2O-Se80, As40-Se60, and Ge30-Asl5-Se55.