Barium fluoride (BaF2) optics

Barium fluoride (BaF2) has nearly 90% transmittance in the wavelength of 200-9500 nm. It has a widest broadband optical transmittance and can transmit from far ultraviolet to long wave infrared, therefore it can be used in various applications, such as infrared spectroscope. The low refractive index of barium fluoride is 1.48, which can provide high transmittance without anti reflection film. In a dry environment, calcium fluoride windows can endure up to 800 degrees of ambient temperature, but exposure to water for a long time will reduce the transmittance in the range of vacuum ultraviolet light. However, compared to the calcium fluoride window, the resistance of the barium fluoride window to the moisture is lower, and the BaF2 window is the most resistant to high energy radiation, but it has a lower transmission of UV. The knoop hardness of BaF2 is 82, and it is very sensitive to thermal shock. It is usually applied to cryogenic imaging system, lens in space optical system and laser optical system, beam splitter, filter, prism and window. The material has a certain degree of water solubility which is suitable to be used in dry environment.