γ-Ray induced color centers in pure and Yb doped LiYF4 and LiLuF4 single crystals

γ-Ray irradiation was used to carry out a comparative study of the induced optical absorption phenomena and color center creation in the ultraviolet and visible spectral regions. The F-center absorption band at 315 and 330 nm in LiLuF4 and LiYF4, respectively, is the dominating induced absorption feature. The amplitude of the induced absorption is reduced by more than a factor of 3 in Yb-doped crystals compared to the undoped ones. Comparison was made with other fluorides, such as CaF2, KY3F10 and BaY2F8. In Yb-doped CaF2, LiLuF4, LiYF4, BaY2F8 and KY3F10 we observed arising of two possible types of Yb2+ centers after γ-ray irradiation. For the entire materials exclude KY3F10 we found Yb2+ centers related to Yb3+, as an effect of recharging one of Yb3+ ion from pair, while for KY3F10 we found mainly Yb2+ centers related to isolated Yb3+ ions, as an effect of Compton electron capturing by isolated Yb3+ ion.