A CaF2 window is an optical window made of crystalline calcium fluoride. These windows are versatile and resistant to laser damage, and exhibit a high, stable transmission from 200 nm to about 7 μm. Shanghai optics produces high quality custom CaF2 windows optimized for UV and IR applications.
The optical properties of CaF2 are comparable to that of BaF2, but with a Knoop hardness of 158.3 it is almost twice as hard as barium fluoride. It is also significantly lighter: the density of CaF2 is 3.18 g/cm3, vs 4.89 g/cm3 for BaF2. CaF2 optics tend to be more economical than their BaF2 counterparts, as, unlike barium fluoride, the optical crystalline substrate can be found in nature. Calcium fluoride is resistant to water, HF and many other acids, although it will dissolve slowly under contact with nitric acid. CaF2 is often a good choice for spectroscopic windows and cryogenically cooled thermal imaging systems; situations where broadband transmittance is essential.
The high damage threshold and low UV absorption of calcium fluoride make it a good choice for excimer laser optics. These specialty UV lasers are used in micro-machining devices and in eye surgery, and we ensure that each of our CaF2 windows is precisely polished and features the high surface quality necessary for these precise laser applications. Our quality check is second to none, and we use state of the art metrology equipment to check that every window which levels our factory fully meets all applicable standards.
The crystalline structure of CaF2 means that a calcium fluoride window will have different properties depending on how it is cut. Our standard calcium fluoride windows are randomly cut. For broadband continuum generation (white light generation), we are also able to supply windows cut along the  axis. Please contact us to discuss the specific need of your application.
In dry conditions CaF2 does not experience significant degradation of form or optical properties until about 800 C, but under normal atmospheric conditions it may begin to soften at around 600. At high temperatures it may be prone to thermal shock, but it is less sensitive to temperature changes than BaF2. The coefficient of thermal expansion is 18.85 x 10-6/C.
Our factory standard CaF2 windows are produced with a clear aperture of greater than 85%, and a diameter tolerance of +0.0, -0.05mm. This ensures a good, tight fit into any prepared mounting. The parallelism is determined to be no more than 5 arc min, and the surface quality is 40-20 scratch dig.
Please contact us for manufacturing limit or custom specifications. Our design team would be happy to work with you as you determine the best optic for your specific application, and our broad range of precision equipment allows us to produce high quality windows to meet any requirements.