alcium Fluoride is a cubic single crystal material grown using the vacuum Stockbarger Technique with good vacuum UV to infrared transmission. CaF2 has a wide spectral range and is an excellent choice for deep UV to infrared applications because of its non-birefringent properties. CaF2 has a transmission above 90% between 0.25 and 7µm, and is commonly used for excimer laser optics due to its low absorption and high damage threshold. Material for IR use is grown using naturally mined fluorite, at much lower cost. CaF2 has very poor thermal properties with its high coefficient of thermal expansion, and should be avoided in high operating temperature environment. Calcium fluoride can be used without an Anti-Reflection coating due to its low index of refraction.
Note that this material is mildly hydroscopic. If used under normal operating conditions, no pitting is expected. However, it is not recommended for water immersion applications.