A guide to selecting CaF2 grades
With a wide transmission band spanning the complete UV to MWIR optical spectrum, Calcium Fluoride is a highly versatile material supporting many applications. Being cubic in crystalline structure, the material is naturally isotropic with respect to both its optical and mechanical properties, allowing it to be used in any orientation without introducing birefringence or non-uniform thermal expansion.
Large material ingots are artificially grown via a vacuum Stockbarger process, enabling the production of lenses / windows / prisms more than 300 mm in diameter. Additionally, given the crystal’s relative hardness and (in)solubility, windows can be polished to an exacting flatness of better than L/20 (0.03 um) and sub-nanometre surface finish (Rq).
Crystal ingots are qualified by purity and categorised into a number of particular grades, as follows. All grades transmit well throughout the IR band, but for UV or spectroscopy applications, material selection can be balanced against cost.