Longwave infrared absorption properties of ZnS and ZnSe

摘要

ZnS and ZnSe are two of the most extensively used longwave infrared optical window materials. Standard grade ZnS exhibits excellent transmittance properties from the 7-12 micrometer region. Post-deposition hot-isostatic pressing converts the standard grade ZnS to multispectral ZnS. Multispectral ZnS is transparent from the ultraviolet to the longwave region. ZnSe is optically superior to any grade of ZnS, but significantly weaker. In this paper, the experimental characterization of the multiphonon absorption edge in standard and multispectral grade ZnS and ZnSe as a function of temperature and frequency is presented. A broadband FTIR transmissometer is used to acquire data at temperatures ranging from 10 to 800 K for both materials. The frequency range is from 600 to 5000 cm~(-1) for ZnS and 400 to 5000 cm~(-1) for ZnSe. Using this experimental data set a multiphonon absorption model is developed that represents the experimental data over all temperatures and frequencies.