CaF2 is a cubic single crystal. It has good transmission from UV to middle infrared wavelength. It is always used in excimer laser components. While, it is a little hygroscopic and susceptible to thermal shock. CaF2 material is relatively soft and somewhat hygroscopic so polishing, coating and handling are more critical than UV Fused Silica components
Transmission range: 170 nm~7775 nm
Thermal Expansion coefficient: 18.85X10 -6 /K
Density: 3.18 g/cm3
 

Beside UV application, CaF2 also is commonly used in IR components such as windows, Lenses and prisms.