Sensitivity of the photorefractive processes

Sensitivity of the different known photoiefractive processes are computed from experimental datas, and compared to an ideal non dissipative process. The minimum absorbed light energy for a change in birefringence of 10-5 in LiNbO3 is found to be Wm-m # 20 mJ/cm3. The real photorefractive processes are shown to be less sensitive by one order of magnitude, excepted the process assisted by photoconductivity, which reaches the photographic sensitivity.