Reversal of degradation of information masks in lithium niobate.
We report on the reversal of degradation of information masks stored in self-defocusing lithium niobate. After a long writing time, the image degradation appears as the splitting of refractive-index patterns stored in the medium. The reversal is achieved simply by illuminating the crystal with incoherent light from a halogen lamp. The reversal occurs because the refractive-index changes responsible for the splitting are of a smaller magnitude and are therefore erased first during incoherent illumination. Additionally, we gain insight into the storage, degradation, and erasure dynamics using a time-dependent numerical model of the photorefractive effect in this medium. Since the data can be recovered from a degraded state in which the original data are unrecognizable, this technique could be utilized in such applications as image scrambling or encryption.
Sando
Daniel
D
Applied Optics and Nanotechnology Program, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. d.sando@qut.edu.au
Jaatinen
Esa
E
Devaux
Fabrice
F