Abstract: There is disclosed a fiber optic waveguide which is particularly suited for infrared radiation transmission at extended wavelengths. The core of the waveguide is fabricated from heavy ionic compounds selected from metal halides in order to achieve such extended infrared transparency. While it is impossible to prepare these materials into optical fibers using conventional fiber drawing techniques, the present invention teaches how such materials may be prepared into optical fibers using an extrusion process at elevated temperatures and high pressures.

Abstract: We have discovered that alkali halides may be purified, particularly of trace anionic and cationic impurities, by scrubbing a melt of the alkali halide with gaseous nascent halogen. The halide radical of the gaseous nascent halogen preferably corresponds to the halide radical of the alkali halide. The purified material may then be used to form single crystals from which laser windows may be produced.