Calcium fluoride (CaF₂), a cubic single-crystal material, has widespread applications in the ultraviolet and infrared spectra. CaF₂ is an ideal material for use with excimer lasers. It can be manufactured into windows, lenses, prisms, and mirror substrates. It is slightly soluble in water and is susceptible to thermal shock. Common CaF2 uses include IR components such as windows, lenses and prisms.

CaF₂ transmits over the spectral range of about 130nm to 10000nm as shown in the figure below. Traditionally, it has been used primarily in the infrared, rather than in the ultraviolet. CaF₂ occurs naturally and can be mined. It is also produced synthetically using the Stockbarger method, which is a time- and energy-consuming process. Unfortunately, achieving acceptable deep ultraviolet transmission and damage resistance in CaF₂ requires much greater material purity than in the infrared, and it completely eliminates the possibility of using mined material.