Hafnium Dioxide: molecular weight 201.49, density 9.68g/cm3, melting point 2812 ℃, evaporation temperature 2500 ℃ under vacuum of 10-2Pa. The evaporation can be heated by an electron beam. The transparent region of HfO2 film is 0.22 ~ 12 μ m, and its refractive index is n = 2.15 (λ = 0.25 μ m, TS = 250 ℃), n = 1.95 (λ = 0.55 μ m).
Because of its high melting point, good chemical stability and strong thermal neutron capture ability, Hafnium Dioxide has high application value in atomic energy industry. In recent decades, with the rapid development of optical thin film technology, the excellent optical properties of Hafnium Dioxide have attracted more and more attention of scientific and technological workers, especially in the near ultraviolet to mid infrared transmittance, high to refractive index and excellent chemical stability, has become the first high refractive index material for the preparation of high-power lasers and high refractive index in other optical film system design. It has a good application prospect.
One of the important applications of HfO2 coating materials is to prepare high-power lasers. With the continuous improvement of the output power requirements of high-power lasers and the miniaturization of devices, as the laser energy density of optical elements is pushed to the limit, the threshold value of some small aperture reflectors is required to be greater than 30J / cm2 (1054nm, 1ns)for high-power lasers built in China, such as pick-off mirror in multipass amplifier, is a typical representative of high threshold reflectors. HfO2 and SiO2 multilayer reflective films were deposited by electron beam evaporation, and the threshold value was 26 J / cm 2(1054nm, 1ns), the pick-off mirror prepared by this process can basically meet the requirements of high-power laser on the threshold of the mirror.