Bulk Optical Properties of Fine Grained Forged Calcium Fluoride

Single crystals of CaF₂ having ⟨111⟩. ⟨100⟩. ⟨112⟩. and ⟨113⟩ orientations have been routinely isostatically foreed in a helium atmosphere at 750°C. The crvstals were deformed 60 percent to ensure a uniform grain size of less than 15µm. A fine cloudiness of “veiling” occurs when the forging is done below the recrvstallization temperature of about 800°C for CaF₂. Nomarski micrographs show that voids are distributed within the bulk of the forgings. Polariscope photographs show internal stress. Total integrated forward scattering measurements have been made on the sample immersed in a cell containing index matching fluid to eliminate scattering from the sample surfaces. These measurements show variations cannot be definitely correlated with the positions of veils in the CaF₂.