Abstract
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.