The optical properties of high-porosity calcium fluoride ceramics

The effective absorption coefficient and the radiation diffusion coefficient are determined for high-porosity calcium fluoride ceramics. A laser photometer designed for recording low transmissions is used for measuring the normal hemispherical transmissivity of cylindrical samples of different thicknesses. Results are given for wavelengths of $0.63$, $1.15$, $3.39$, and $5.25$ $\mu$m. The thus obtained data are used to calculate the dependence of the bihemispherical reflectivity of a plane layer on the layer thickness.