Quasi-real-time visualizations of dynamics of light-induced index changes during thermal fixing in LiNbO₃ crystal

The dynamics of Gaussian-beam-induced index changes in LiNbO₃:Fe crystal during thermal fixing are visualized in quasi-real-time by using digital holography. The on-line method is employed to fix the light-induced index changes, and an incoherent white beam emitted from a cold light source is used to develop the fixed index changes. By numerically reconstructing the recorded digital holograms, the distributions of light-induced index changes corresponding to different stages of thermal fixing can be obtained. The results illustrate that the reversal of the Gaussian-beam-induced index changes during thermal fixing are visualized in quasi-real-time successfully by employing the digital holography, and the optimal developing time can be obtained by monitoring the evolvement of light-induced index changes.