THERMAL FIXING OF VOLUME HOLOGRAMS IN POTASSIUM NIOBATE

Volume holograms are thermally fixed in a pure and an iron doped potas sium niobate crystal through the screening of a photorefractive space- charge field by a nonphotoactive species at elevated temperature (110 degrees C). The nonphotoactive species is identified as the hydrogen i on, Fixed holograms are reconstructed at different temperatures, A dif fraction efficiency of 16% in a 6 mm thick KNbO3:Fe sample is measured . The time constant and activation energy associated with the thermal induced decay of the hologram are determined to be 2.9 X 10(-7) s and 0.81 eV for the KNbO3:Fe sample, and 1.35 X 10(-7) s and 0.79 eV for t he pure KNbO3 sample. (C) 1996 American Institute of Physics.