New coating materials for IR laser optical components

Concepts of reactive atmosphere processing are applied to the preparation, purification, and thermal characterization of three rare-earth fluorides (LaF₃, CeF₃, and PrF₃) and BiF₃, BiI₃, and KGaF₄. The rare-earth fluorides have optical absorption coefficients between 0.6 and 0.9 cm^?1 at 9.27 μm; of the rare-earth fluorides, only LaF₃ is a good coating material at 3.8 μm. BiF₃ and KGaF₄ appear to have low absorption at 9.27 μm and 3.8 μm. BiI₃ shows a flat response between 2.5 and 20 μm.