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For the first time to our knowledge, the results of the investigation of some photorefractive characteristics of lead germanate crystals doped by neodymium (PbsGe3011 :Nd) are reported along with those of Pb5Ge3011 :Cu and Pb5Ge30 11 crystals. The furnace charge concentration for Nd and Cu amounts 0.2% and 0.5% respectively. We have not used any monodomained crystals. There was no external electric field applied to crystals. All the crystals under study have exhibited the photorefractive properties when irradiated by a He-Ne laser. The total intensity of the irradiation was about 2 mW/mm2. The diffraction efficiency of the gratings recorded on PbsGe3011 :Nd, Pb5Ge30 11 :Cu, and Pb5Ge30 11 crystals was equal to 2.8, 2.5, and 2.2%, respectively. The holograms were recorded in counterpart beams, too. So, the crystal resolution appears to be not less than 3175 lines/mm. The response time for the crystals have ranged from a few seconds up to several minutes depending on mutual orientation of the optical axis of the crystal and the grating vector the recorded hologram, and upon the grating constant. The time of photoinduced erasure of the crystals when effectuated by one of the recording beams, has appeared to depend on the above parameters and ranged from 5 sec to 30 min. The grating on Pb5Ge30 11 :Nd, once recorded, have preserved its properties, if stored in the dark, for about 10 days. The gratings recorded in counterpart beams have lost their properties in the dark in 10 seconds. Only minor photorefractive effect has been registered under the irradiation by green line (A.=4880 A) of an Arlaser.
Keywords: holographic gratings, formation and erasure time. diffraction efficiency, holographic image processing
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