Calcium Fluoride (CaF₂) is commonly used for optics looking at the IR and UV spectrums and has a very low change in refractive index with wavelength. It shares similar optical properties with Barium Fluoride although it has a transmission that is 2.5µm less into the infra-red. Calcium Fluoride is however cheaper than Barium Fluoride as the optical grade occurs naturally as opposed to BaF2 being man made.
|Commercial Grade||Precision Grade||High Precision Grade|
|Parallelism||<3 arc min||<30 arc sec.||<2 arc sec.|
|Coating||Upon customer's request|
Calcium Fluoride is used for optical windows, drilled discs, lenses and prisms in transmision range 0.15-9µm. Degradation due to to moisture in the atmosphere is minimal, and polished surfaces of the CaF2 windows may be expected to withstand several years exposure to normal atmospheric conditions.Since they are nonaxial, CaF2 crystals do not require consideration of axial direction. Because of CaF2 low refractive index, Calcium Fluoride windows can be used without an anti-reflection coating.Calcium Fluoride is attacked by atmospheric moisture at 600°C, where it begins to soften. The top use temperature is 800C, when moisture is not present. Irradiation of Calcium Fluoride windows causes some loss in UV transmission. CaF2 is sensitive to thermal shock.
Typical applications: VUV - UV - IR imaging systems, excimer laser windows, CaF2 viewport, demountable cell windows in spectroscopy and all kinds of lenses. Alkor produces CaF2 windows and mirrors for European manufacturers of gas detectors and gas analyzers.
Maximum diameter of CaF2 windows by Alkor - 220mm (8").
Alkor manufactures vacuum UV grade CaF2 windows and lenses (193nm and 157nm) upon request.