Theory of high-temperature photorefractive phenomena in LiNbO 3 crystals and applications to experiment

We develop a theory of high-temperature photorefractive phenomena in ${\mathrm{LiNbO}}_{3}$ crystals related to the problem of thermal fixing and storage of optical information. The theory covers the temperature range 20\char21{}300 \ifmmode^\circ\else\textdegree\fi{}C relevant to the experiment. It is based on a systematic exploiting of small physical parameters, typical of the subject, and distinguished by general and simple expressions for characterization of the fixing, developing, and decay processes. It is shown that thermally excited electrons are competitive with protons (responsible for the charge compensation) within a wide high-temperature region 200\char21{}300 \ifmmode^\circ\else\textdegree\fi{}C. They are not only responsible for the dark decay of information, but also for pronounced high-temperature peculiarities of the recording and relaxation processes. A good qualitative agreement between the theory and a great amount of accumulated factual data are obtained.