Laser-radiation bleaching of LiF crystals containing color centers

An experimental investigation was made of saturation of the absorption of $\lambda$ = 1.06 $\mu$ laser radiation by an LiF crystal containing color centers. The results were interpreted using a two-level approximation. A method for determining the color center density was developed. The excitation cross section of $F_2^-$ centers and the saturation threshold were used to estimate the cross section for the stimulated interlevel transition (6$\cdot10^{-19}$ сm$^2$) and the nonlinear absorption threshold (0.15 J/cm$^2$).