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Calcium Fluoride Windows
Thorlabs offers calcium fluoride (CaF2) High-Precision Windows either uncoated or with a broadband anti-reflective coating. The uncoated windows provide high transmission from the ultraviolet (180 nm) to the infrared (8 μm). The AR-coated windows feature an antireflection coating on both sides that provides increased transmission within the 1.65 - 3.0 µm specified wavelength range. Given its low absorption coefficient and high damage threshold, uncoated calcium fluoride crystal is a popular choice for use with excimer lasers. CaF2 windows are also commonly used in cryogenically cooled thermal imaging systems.
Calcium fluoride has a low absorption coefficient and high damage threshold, making these windows a good choice for use with free-space lasers. Optical calcium fluoride offers low dispersion (with an Abbe Number of 95) and low fluorescence, as well as excellent water, chemical, and heat resistance. In dry environments, CaF2 can be used up to 1000 °C, but in the presence of moisture, degradation will occur for temperatures exceeding 600 °C. Each window has a randomly oriented crystal axis.
Thorlabs offers High-Precision Windows fabricated from various substrate materials for use in a large variety of laser and industrial applications; see the selection guide to the right for windows manufactured using other substrates. We also offer laser windows, which have wavelength-specific AR coatings centered around commonly used laser wavelengths, and Brewster windows, which are used to eliminate p-polarization reflectance.
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This graph shows the measured transmission of an AR-coated calcium fluoride window at normal incidence. The shaded region denotes the AR coating range, over which Ravg < 1%. Performance outside of the specified range is not guaranteed and varies from lot to lot.